|Water Commander™ is the "no battery"/ "no electricity"
water powered backup sump pump.
Water Commander™ is reliable, powerful and uses no battery
Water Commander™ is fully automatic, protecting your basement
from flooding during a power outage or primary pump failure.
Water Commander™ uses your home's city water pressure as
the source of its pumping energy. Because it does not depend on
a battery, it will operate at full power, as needed, for years to come.
Water Commander™ can remove up to 1800 GPH (gallons per
hour) when connected to a 3/4" water supply and up to 2830 GPH
with a 1" water supply.
Advantages of Water Commander™
Water Commander™ is a non-electric backup sump pump that
uses your home’s water pressure to operate – no battery or
electricity is needed. It will pump, as needed, during power
outages or primary sump pump failure. It will also work in tandem
with your electrical sump pump if necessary in an extreme
Water Commander™ is powerful. It can easily match or outpump
your electric sump pump. (see pumping capacities model MG22 or
Water Commander™ is dependable. The pump will activate and
empty your sump automatically, there is no need to be home as
you would if using a generator. Even if you are gone for weeks,
Water Commander™ will stay on duty and operate at full power as
Water Commander™ operates silently. It handles solids up to a
diameter of .033” (MG22) or .042” (MG36). It easily mounts on
ceiling above sump well or can be mounted in various positions
(see Install Considerations) as the situation requires. Suction and
discharge lines can have multiple 90° turns.
Beats Battery Backups
Unlike battery backups, Water Commander™ will operate as
needed for an unlimited amount of time. No maintenance is
There is no future battery replacement needed. A battery backup
will give you 7 to 8 hours run time when new, but loses power
capacity consistently as time goes by, until the battery must be
replaced after two to three years. Also, there is no possibility
of battery acid spills or battery disposal issues.
Water Commander™ will run reliably without limit for many years
after a battery backup has lost its power.
For more information on this fine product, please visit them at their
corporate website. . .
Tankless water heaters have been sweeping the nation with a huge growth over the last 5 years or so. These are water
heaters that do not have a tank. Many of the larger tankless companies have seen their sales grow by hundreds of percent
each year! These compact units mount on a wall either inside or even outside the house and supply hot water on demand
literally without end! Many people believe that within the next 5 to 10 years 50% or more of all American homes will have a
tankless water heater in them! Even the big tank water heater companies have tried to jump on board by partnering with larger
Japanese companies to have units private labeled for them Tankless water heaters are available in electric, natural gas and
propane fired models. The electric tankless water heaters have advantages over tank type electric models but very few
provide enough capacity to serve multiple fixtures with only one unit and may require a larger electrical service to operate
them. This has kept most builders from using them in new construction. Although they do tend work well in small homes,
condos or apartment applications where gas is not an option. For the purpose of this tutorial we are going to talk about the
gas fired units. Watch for a future article containing information on electric tankless heaters. Tankless water heaters work
on demand by using sensors and computer boards to monitor the flow of water and change the rate of firing to
supply just the amount of hot water required for the current demand. (They are also called on demand heaters)
This means that they burn less gas to supply hot water to something like a sink than they would if you are using
multiple fixtures at the same time. This modulating firing rate also make them very efficient to operate as you are
only using the exact amount of fuel needed at that time. A term that should be avoided is “instantaneous”. Tankless
water heaters are not instantaneous. It does take them about 2 seconds to go from their at rest “off” mode to producing hot
water at the set point temperature. This is not a big issue however. The problem is if a consumer thinks by hearing the term
“instantaneous” that they will get water at every outlet in the house instantly if they get a tankless heater, they will be
disappointed. Most homes have many feet of piping between the water heater and the outlets and do not have a recirculating
system. The amount of time it takes from when a faucet or other hot water fixture opens to when the set point water gets to
that point is called “Lag Time”. In today’s large homes with low flow fixtures it is not uncommon to see a lag time of over 3
minutes to get hot water to remote fixtures in a home. Changing the type of water heater will not improve the speed of the
delivery of water unless the location of the heater is altered or if a recirculating system is installed. Because of their small size
of course, many times when a tankless heater replaces a tank, it can be moved to a more central location or nearer to the
fixtures it is to serve. This may cut down on the lag time considerably. Tankless Water heaters save space in a home because
they take up NO floor space. They also do not require protection from vehicles if installed in a garage and are so small they
can be installed in a crawl space or attic as well. If you really need space, many can be installed outdoors giving you all of your
interior space back. Just be sure to choose a model designed for outdoor installation and with freeze protection for your area.
(More on this later also)
Tankless water heaters save fuel because they do not have to maintain a supply of hot water in a tank and are
typically “always off”. Tank type heaters fire on and off all the time to maintain the temperature of water in the
tank within about 10° - 15° of the thermostat setting. (This is called “Stand-by heat loss”) This also can result in
some noticeable temperature difference. Tankless water heaters provide hot water to the set point temperature
plus or minus 2°. Another thing that makes a tankless hot water heater more fuel-efficient is that they are “fully
modulating”. In other words they only use the fuel needed to heat the water to the set point at the current flow
rate. If you are washing your hands using under 1 gallon per minute (GPM) you will be at a lower firing rate than
you would be if you are filling your tub at 3 GPM. This works much like your car. When you are sitting still the car
is idling. When you want to go or go faster you give it more gas and when you get where you are going you turn it
off. With their “always off” condition and their modulating capabilities it is common to see up to a 50% reduction
in fuel use when changing from a tank type heater to a tankless unit. If you are going to change from a 50-gallon
gas heater to a tankless you are probably not going to realize quite that much energy savings. In fact a 50-gallon
tank water heater does not use much more fuel at all compared to most tankless heaters. However a 50-gallon
tank heater only can really give you about 40 gallons of hot water per use before you begin running out of hot
water. The tankless heater will deliver more than 300 gallons per hour for most of the year and you can never run
out! If it is an electric tank water heater that you are replacing, your savings may be higher than 50% depending
on the size of the tank. If you really want to know what your savings may be look for the yellow “Energy Guide”
sticker on your existing heater and look for the one on the tankless unit you are considering. This will give you a
good idea of what to expect. Of course your personal use will effect this as well. If you have a family of 6 that has
never had enough hot water with a 50 gallon tank heater, your bill might just go up because now your family will
not be taking cold showers or have to shorten them. If you have a vacation home that is occupied only on
weekends or using the tankless for something like a school locker room, your savings will be greater because
the tankless unit is “always off” eliminating wasted energy. Part of the decision making process is; What do you
want? Endless hot water may be worth the additional investment to you even without an energy payback.
Builders like the tankless water heaters for several reasons, not the least of which is space savings. When you charge by the
square foot for a home, saving space means that home is worth more. A tank type heater installed in garage requires a floor
stand, a pipe to protect against vehicle impact and normally venting all the way to the roof. In a two-story home, this means
more framing, drywall and paint to enclose it. A tankless water heater is wall mounted and can be sidewall vented, keeping the
cost of venting to a minimum. It also does not take up any of the garage floor space. Being able to install tankless heaters
outside or build them into a wall gives even more options that the builder never had before. This means even less venting cost
(practically none) and even more space savings. Some builders will locate them centrally in a crawl space to cut down on lag
time. Others will locate them near a master bath or kitchen. Some will install them in attics or outside to free up more space.
Since there is no tank to burst, installing a tankless heater in an attic is not as risky as installing a tank there. Even with a drain
pan, a tank water heater in an attic is a catastrophe waiting to happen! A drain pan that is 3” deep will not do much good if the
bottom blows out of a 50-gallon or larger tank water heater. (This is not an uncommon occurrence!)
Many of the better tankless companies have models that can be installed outdoors. This frees up all of the interior space and
does away with venting costs or combustion air issues. These units will have their own freeze prevention systems however you
will need to protect your water piping from freezing. This can be done with a pipe cover kit or recessed wall box, which can be
insulated. It is also recommended that you install self-regulating heating cable on the piping to keep it above freezing. Outdoor
units require power at all times to operate their freeze prevention system. In the event of a power outage in freezing weather,
you will need to prevent you tankless from freezing by leaving a faucet dripping or draining the unit until the power comes back
on. A “back-up” power supply or generator is also an option and there have been some solenoid valve products developed
that will automatically valve off and drain down a tankless water heater in the event of a power outage.
Another reason that builders like tankless water heaters is that they are able to provide hot water to todays popular large tubs.
A standard bathtub holds about 35 gallons to the overflow. The popular soaking tubs hold anywhere from 45 gallons to over
80 and just filling up the tub leaves most without any hot water with a tank type heater for a period of time. A tankless can fill
all the tubs of a home and then provide back to back showers, do the dishes, and wash the clothes. A tank type heater has to
be very large to do all of these things without running out. We are only limited to the flow rate our tankless unit can provide.
Choosing a tankless heater with the proper capacity for our house makes it possible to handle multiple hot water needs at
once without the worry of running out of hot water. Until now, most people made “water rules” to determine who showers when,
or when they could do the clothes or dishes. This goes away with a tankless water heater. Some people mistakenly think that
they will only be able to run one fixture at a time with tankless heater. While this may be true of the “Home Center” models, this
is far from accurate when speaking about the professional grade heaters from Rinnai, Noritz and Takagi. These models have
the capacity to operate 3 showers or more at the same time! Some will correctly claim that tankless water heaters limit the flow
rate to make sure you get the setpoint temperature and say that this means you will not be able to do multiple things within the
home using hot water. This is simply not true. Choosing the right unit is important as discussed a little later, but making this
claim is like comparing all tank water heaters to the old 30-gallon tank heaters that would run out after every use. Today’s
tankless water heaters provide more than enough capacity to meet any hot water need from a one-bathroom house to a hotel.
You just need to choose the correct system for your application just like any other hot water system. Here is something else to
consider when choosing your tankless heater. Asking it to operate three showers, the kitchen sink, the washing machine, the
dishwasher and a laundry sink at the same time is not only unrealistic…your water pipes can’t carry that much water! Most
homes only have a ¾” hot water main and most are now in PEX or CPVC materials. These piping system can not carry more
than about 8 - 10 GPM total, including cold water. Also, many new homes typically see less than 2 GPM at a showerhead due
to pressure looses in the piping. In other words if you choose a tankless heater that can deliver between 6-8GPM in the warm
months and 4+ GPM in the winter months you will be quite happy in a typical 3-1/2 bath or less home. You should avoid the
tendency of some to oversize a tankless system based on unrealistic system demands. If in doubt, contact the manufacture for
help. Capacities of these water heaters have improved greatly over the first tankless models that showed up about 10 years
ago in the US. The Largest of these companies (Rinnai) has models that can run from 4.2 GPM to 9.8GPM inculding
residential and commercial units. Noritz has a commercial grade model that can produce up to 13.2 gallons per minute (752
gallons per hour from one unit!) Most of these products can be installed in multi-unit installations for high flow rate demands
like luxury homes, large shower system with body sprays, locker rooms or hotels. (More on this later as well.) Many tankless
water heaters are also installed with a remote control unit that makes it easy to change the set point temperature of the unit.
One manufacturer, Rinnai, has a remote that lets you set an alarm to the capacity of your tub that will actually stop the flow of
water once the tub is filled! You then set the temperature you would like and fill with just the hot water. When the unit
measures the gallons set an alarm sounds to remind you shut off the water and reset the remote and the flow is stopped.
Rinnai, is able to provide multiple remotes to serve the same heater to provide for multiple locations to change the
temperature of the hot water if you like. They even have a wireless remote to allow for easy locating of the remote in retrofit
instalations. These digital remote control panels also provide diagnostics for the water heater in the event that there is a
problem. They flash a fault code to help service personnel find and fix any problems that may come up quickly. The better
tankless heaters by Rinnai, Noritz and Takagi totally control outlet temperature so they can NOT be "overshot" giving you less
than the set point temperature. You always get setpoint temperature plus or minus 1 or 2° (Unlike a tank which is + or - about
10°) Electric units and home center models do not have this ability. I would advise avoiding the home center models
completely as they lack the technology and BTU’s to give you good performance. In units that can not control their outlet flow,
you will need to “throttle” the flow rate yourself at the outlet. This also means that if you are taking a shower and someone else
turns on another fixture needing hot water, you may get a big surprise as the water temperature drops considerably in your
Choosing The Right Sized Unit
The first thing we need to do is establish the peak hot water demand for the job. In a home this is usually the number of
showerheads, X the flow rate X 80%. Example: 3 showers @ 2.5GPM each = 7.5GPM X 80% = 6GPM peak demand.
You want to choose a tankless unit that can meet or at least get close to this demand during the warm half of the year.
(Remember it is VERY uncommon to have a demand like this actually happen in a home, plus we are not going to install a unit
that can not control the flow rate anyway.) If you are within 1 GPM of this rate you will be happy. It is not possible for most
people, even plumbers to tell the difference between 1 GPM and 3 GPM without a direct caparison next to it.
The proper size unit for the home above would be something like the Rinnai R85. The Rinnai website (www.foreverhotwater.
com) even has some great sizing calculators on it as well as an energy cost calculator and even an evironmental impact
calculator to demonstrate how installing their product is good for your wallet and the planet.
Professionals: Please talk to your local wholesaler about attending a training class on these products. They must be installed
properly to work well and installing them improperly may result in damage to the tankless heater, poor performance, premature
failure or injury to the homeowner.
What about the tank manufacturer’s?
Good question. In the United States, over 9.5 MILLION tank type water heaters are sold every year! About half of them are
electric. That is a huge market. Every time a tankless company sells a tankless water heater, the tank companies loose a little
bit of their market share. (They don’t sell a tank) It did not take very long for this to get the attention of the big tank companies.
These companies quickly looked into the market. They had some serious questions to ask and decisions to make. The
questions would be along these lines: Is this a fad that will go away? Do these things really do what they say they can do? How
long have these products been in use in other parts of the world and what is their track record? How long will it take us to
produce a market viable unit?
These great companies are full of very smart people. They got their answers and had a group “Uh-oh” moment. They made a
conscious decision that they would not roll over and let the “invaders” take over their market without a fight.
They found out that over 25 years of research and development went into these products. With estimates of 5 years before
half of the market flipped to tankless, they had to act fast. They knew they could “Reverse Engineer” the products but that
takes a lot of time and they would have to be careful to keep from violating patents.
The first step by a few of them was to attempt to slow things down. They did this by putting out letters, and articles touting the
“negatives” of tankless heaters. While this was going on on the surface, they were behind closed doors with the lawyers
striking deals with the tankless companies to have units private labeled for them in an effort to slow down their shrinking
market share until they can catch up with the technology.
The results so far are this: Bradford White has Rinnai manufacturing its “Everhot” tankless water heater line. It IS the Rinnai
line with the BW name on it. State and A. O. Smith have (or at least had) Noritz manufacturing theirs before Noritz severed the
One very large tank company even went to the trouble of taking “their” new tankless water heater and putting against their
tried and true gas fired tank water heaters in a “test”. The parameters of the test were set up to with high levels of water
hardness. They knew that the tankless would require cleaning because of it and their tanks would not. (Because you can’t!)
One thing they did not bother to tell anyone or include in their “short term” test was that had this test been allowed to continue,
the hardness would have certainly ruined the tanks and required them to be replaced a lot sooner than the tankless which
could simply be cleaned. This was done also to try to slow down the onslaught of tankless while they tried to figure out what to
do next. Most of these tank companies are still producing papers trying to slow the growth of tankless. (Even the ones with
their “private labeled” products!) They will sometimes make claims using the lower quality of the available units to try to show
them as “point of use” of all them a “Niche product” even eluding to tankless as a fad at times. They will make statements
claiming that they don’t believe in tankless water heaters as “whole house” units. These are just attempts to “stem the tide” as
long as they can unit they can catch up. Some will print more than others but it is all for the same reason. They need to get
people to NOT consider tankless water heaters for as long as they can to protect their own interests. Rumor has it (And they
are just rumors) that they are all reverse engineering at this moment and will have units ready sometime in the next 5 years.
We’ll have to wait and see on that one. At least for now, they are trying to keep up with the private labeled Japanese units and
they are participating in the market.
So, the big tank companies are worried, as they should be. They are doing what they can, and they are not going away.
Tankless is to water heating what indoor toilets have been to bathrooms!
Tankless water heaters usually have a warranty that covers the heat exchanger and the parts separately. The heat exchanger
is the main part, much like the tank in a tank water hater. Normally the warranty is for about 10 years on the heat exchanger
and 3-5 years on the rest of the parts. This average warranty also reflects on the average life expectancy of tankless heaters.
(20 years!) THe best warranty of all the tankless manufacturers is Rinnai with delux model that has 12 year warranty on the
heat exchanger and 6 years on all the rest of the parts! THeir standard units also boast the best warranty at 10/5.
A brief word about warranties. Manufacturers (Of all Products) tend to set warranties at about half of the life expectancy. Your
cars, your dishwasher, your water heater, all have a warranty that is about one half of the average life expectancy of that
The nice thing is that with a tankless, even if the main part (the heat exchanger) fails after warranty, you have the choice.
Replace the heat exchanger or replace the whole unit. You do not have this luxury if your tank fails in a tank water heater.
Minimum Flow Rates
A very important consideration when deciding on your tankless water heaters is minimum flow rate. All tankless heaters need a
minimum flow rate and pressure to work properly. You should look for a model that has a minimum flow rate of .5 GPM for a
residential application and one that will operate well down to about 30 PSI system pressure.
Even with a minimum flow rate of .5 GPM it is possible to have a flow related problem but it is a lot easier to solve. If you have
single handle bathroom (lavatory) faucets you are going to need to open them all the way to get the minimum flow rate to fire
the heater, especially in the summer time. This is why I advise to not use tankless water heaters with high minimum flow rates
in homes. Commercial units can have minimum flow rates of .75GPM . That is about as high a minimum flow rate as you would
want in a home. Most homes requiring these units (Large luxury homes with “carwash” shower systems) do not have very low
flow fixtures and typically do not need to worry about minimum flow rates.
Also, Debris in faucet aerators and showerheads can cut their flow rates down to a point that will keep the tankless from firing.
Make sure your fixtures are free from debris.
Most 2.5 GPM showerheads will not supply 2.5GPM of flow in a new home. This is due to system pressure looses. Every foot
of pipe and each fitting in the water main has a pressure loss. At far ends of the home these add up and can cause lower flow
rates at fixtures like showerheads. This is not a big problem though and rarely causes issues with the better tankless water
heaters. Most people never know the difference and as stated above, it is almost impossible for most people, even plumbers
to tell the difference between 1.5GPM and 2.5 GPM in today’s showerheads without measuring the flow. As long as the
velocity of the water is acceptable most people are quite happy and of course some showerheads are better than others.
Most tankless water heaters have an inlet water filter. This should be checked and cleaned regularly to make sure that flow is
not slowed or stopped by this filter. This is the first place to look whenever there is a problem with your tankless water heater.
Look for it in your owner’s manual.
Hard or Acidic water
Water quality issues can be a concern for tankless water heaters in some areas. To understand the concern you first need to
understand how certain water conditions effect tank and tankless water heaters.
Hard water is water with large amounts of dissolved solids in it. If you have hard water and pour it into a clean glass, you can
not see the hardness. The hardness is “in suspension” in the water and as the water is heated the particles cling together and
drop out of suspension. In a tank water heater they sink to the bottom and form a layer of scale where they build up. In a
tankless most of the particles are flushed from the system as they drop out of suspension.
Since a tank heater heats water when you are not using it to maintain the stored water, they tend to get that sediment on the
bottom of the tank. This is because the particles are dropping out of suspension when there is no movement of water in the
tank. Even when you are using hot water with a tank heater there is very little movement of the water. As the sediment builds
on the bottom of most gas fired tank water heater it becomes an insulator and causes the steel to be over heated without a
good transfer of the heat to the water on the other side of the sediment. Over time, the fire burns through the tank or the
welds fail and the tank begins to leak. If the leak is not spotted, then the tank will eventually rupture flooding the house!
In a tankless water heater, the particles are being flushed from the system as they drop out of suspension due to the high flow
rate through the coils. Some hardness may adhere to the walls of the tubing but it will be a lot slower process than with a tank.
If the water is so hard that the tankless coil becomes fouled the heater will send an “Overheat” or “Lime” error code (Usually
represented with a number) and lock out alerting the homeowner that something is wrong. Rinnai has a special "LC" error
code to alert the home owner before damage is done to the unit. A technician can then come out, diagnose the problem (With
help from the heater error codes) and de-scale the unit, renewing it in about 45 minutes.
Scaling of gas tankless water heaters is a fairly rare thing. When it happens the water is typically so hard that the homeowner
should consider a water softener system. Water that is that hard is effecting every other appliance in the home. Toilet fill
valves, faucets, washing machines, dishwashers, ice makers, etc. In fact if the water quality is that poor, a softener system will
pay for itself by making these other things last longer and require less maintenance and less frequent replacement, including
the tankless water heater!
Acidic water is another problem. Most water is not going to have this kind of issue, especially if you are on a public supply.
However, if you know you have acidic water, you need to consider installing a neutralizing system to protect your tankless
water heater. Any acidic water that will eat copper piping will eat the copper piping in a tankless water heater as well and
shorten it’s life as well as possibly voiding the warrantee.If you do not know if you have hard water or acidic water, chances are
you don’t and should worry about it. If you want to be sure, there are many testing services available for free from companies
that sell the treatment systems or you can contact your local water company or extension agency for testing.
Even if a tankless heater does develop a leak in the heat exchanger, that part can be replaced and your tankless is back in
service without a replacement. With a tank heater, once the tank gets a leak, you throw it away and get another one. This also
makes tankless heaters more environmentally friendly because less material is going into landfills. Think about the millions of
tank water heaters going into landfills every year! What if water heaters lasted twice as long and were repairable? How much
landfill space could we save?
“Cold water Sandwiches”
The “Cold water sandwich” is a phenomenon that can effect a tankless water heater home that is less likely to effect a home
with a tank heater. It happens in homes with tank heaters but can be less noticeable. This is where a section of piping has hot
water that has cooled off between uses and between the piping in the walls or water heater. Piping in the walls looses its heat
slower than piping in a crawl space or basement. If there is a hot water draw and then the flow is stopped for while, the water in
the most exposed piping cools off faster than the water in the piping in the walls. If someone opens a fixture at the right time,
the first water out of the tap is hot, then goes cooler as the water from below gets to the outlet, then heats up again as water
from the heater gets to the fixture. In some homes a tankless water heater can exaggerate this a bit. Imagine the large house
with a tankless heater and a short draw. One person turns on a faucet at one end of the home and gets hot water to wash
their hands. A few minutes later another person goes into another area and washes their hands. The water in the pipes is still
hot. They are almost done when the temperature goes cold for a few seconds then back to hot again. Viola’ one cold water
sandwich at it’s best. It does not happen every time and it does not seem to be a regular issue except in the case of homes
with recirculating hot water systems where this has not been accounted for. We will get into that later. Here is why it happens:
When the flow stops a tankless heater stops firing and the draft fan continues to run as a “post purge” to ensure that all
exhaust is moved out of the venting system. It runs for about one minute and during this time it cools off the heat exchanger.
The heat exchanger holds about .2 gallons of water. (a little less that a quart) When the heater senses flow again it fires back
to provide hot water for the next draw. The water in the piping may still be hot, but the very first bit of water to leave the heat
exchanger is not heated. It does take about 1 - 2 seconds for the tankless heater to get going. Now this first quart of water
enters the pipe with the water that is still hot from the last draw and begins to mix with it as it travels down the line. Eventually
the lower temperature water gets to the user and they notice the temperature fluctuation. Is this normal? Yes. Is it
acceptable? Maybe. In most homes this is perfectly acceptable since it is not a common occurrence and the short draws are
usually hand washing and when this does happen it is only a minor issue. However if you have just paid for a recirculating
system for your home and every time the pump comes on you get a little slug of cooler water in the piping, it might not be
acceptable. When you jump into the shower at the far end of the home expecting instant hot water and get the surprise from
the cold water sandwich, you probably will want to know how to deal with it. If you are an installer of tankless heaters, then you
will want to read and understand the next part well to provide a perfect hot water system every time.
Recirculating systems can work great with tankless water heaters when properly designed and installed. The proper system
will provide instant hot water at most if not all outlets in the home and save the customer water by not having to run the hot
water until hot water gets to the outlet.
The traditional way is to install a recirculation system is to install pump and a return loop back to the inlet side of the heater
with a couple of flow check valves. This will work of course but you have to install pump with enough “head” capacity to get
through the high head loss of the tankless. Higher head pumps also use more electricity to operate than their lower head
counterparts. How big a deal is that? Well if a higher head pump uses $.02 more to operate per kWh then the other pump,
over a 20-year operating period that calculates into the thousands of dollars over the life of the pump!
Another consideration is most tankless water heaters get their energy efficiency and their longevity by being “always off”.
Installing a recirculating system this way puts a lot more wear on the unit and may cut it’s warranty in many cases. Add the cold
water sandwich to the equation and there is a better way.
One of the first things that installers dealt with was the cold water sandwich. This was managed by installing a very small
storage tank (About 5 gallons) right after the tankless heater. This way, if a small slug of hot water got out of the tankless it
would mix with the 5 gallons of hot water in the tank and be diluted to a point where no temperature change would be noticed.
That fixes the cold water sandwich but still leaves the high head pump and the warranty issue to deal with.
At some point someone came up with the idea of turning that small storage tank into a 5 or 6 gallon 110V tank water heater.
They are very small, insulated, and can plug into an outlet. Then they hooked up the recirc loop between the tankless heater
and the small tank heater effectively by-passing the tankless, saving the warranty and keeping the energy efficiency of the
unit. The small tank heater does not have to heat the water very much. When the system is first turned on, a hot water fixture
is opened filling the entire system with hot water including the small tank. The tank and recirculating system now only has to
use enough energy to maintain the loop temperature. This is usually only about a 5° rise. With insulation on the hot water
piping, it is a very efficient solution! Instant hot water, as efficient as you can be with very low energy demands, and all the hot
water you will ever need.
If you would like a diagram of this system, contact Rinnai through www.foreverhotwater.com. They will be able to provide this to
you or your contractor.
Twin tankless systems
There are many reasons to go to a “Twin” tankless system. You may have a big house with 4 or more baths and a large
family, or you may have a large flow capacity shower system installed and need a higher flow rate. A good gas tankless water
heater can easily operate 3 showers in the winter months, and even 4 in the summer months due to warmer incoming water
temperatures. If you need more that that you may want to consider a twin system.
When you install a twin system you should always choose a tankless water heater that is made to operate this way. If you were
to just choose two tankless heaters and pipe them together you would compound their minimum flow rates. If you have two
tankless heaters with a .5GPM minimum flow rate and piped them in parallel without installing them properly, you will end up
with a 1GPM minimum flow rate before either heater will fire! Plus you would have a very unbalanced flow through each
heater. If you hooked them up in series, you would never be able to get a higher flow rate than the full capacity of one heater.
Rinnai, Noritz and Takagi all have units that are made for multi-unit and twin system installation.
Hooked up in a twin system, when there is a low demand one unit will work by itself with the other automatically valves and
turned off. When the demand increases to about 50% of the capacity of the first unit, the second unit is brought online and
load is balanced between them. The heaters will work together up to their peak capacity. They also will act as a “lead/Lag”
system in that the “lead” unit will change after every few operating hours so it does not get more wear than the other one.
Another great benefit of this system is that if one unit develops a problem, the system will lock it out and valve it off, sending
an error code to the remote. The other heater will operate normally up to its capacity. This is called “Redundancy” and it
means you are never out of hot water, even if there is a problem. Wiring these system is not difficult and the instructions do a
very good job in guiding the installer to hooking up the system for the first time.
There are very few homes that need more hot water than a twin tankless system can produce. With the average heater from
Rinnai, Noritz or Takagi, you will get from .5GPM – 16GPM depending on incoming water temperature. That’s from the lowest
flow rate required for hand washing up to 960 gallons per hour of hot water! All that and you still have not taken up any floor
space of the home, and have no tanks to burst.
The question comes up often “Should I just put one at each end of the house and let them be separate?” You can of course
do this if you like. It is two separate hot water systems and you do not get the redundancy of the true twin system however you
may eliminate the need for a recirculating system in a larger home. The choice is up to you and you should simply consider
what benefits are most important to you and how your home will be used. If it is just a lot of bathrooms like a 5 or 6 bath home,
but you do not have any high flow fixtures, it may make more sense to just place them at opposite ends and have two hot
water tankless systems. This is very likely to cost less money up front then a twin system with a recirculating system in a large