How a Tankless Water Heater Works
Overview of the Tankless Hot Water Heating System
Most people in North America currently use a storage tank water
heater to provide hot water in their homes. At ProEnviro Construction,
we have a better solution and we are here to help you understand
the pros and cons of a tankless water heater. A storage tank
water heater keeps water hot 24 hours a day, even while you're
at work or sleeping. A tankless hot water heating system, on
the other hand, does not store hot water. It heats the water
as you use it, providing endless hot water. There are additional
links at the bottom of this page which can help you in the selection
of specific units that would be best for your home. Please
review this section thoroughly.
What are the advantages of
a tankless system? A tankless water heater also known as
point of use water heater or on demand units, turns on when
you open a hot water faucet and turns off when you close the
faucet, so the energy that is consumed is only for the hot water
that is being used. Since there is no storage of hot water and
thus no constant heating and re-heating of stored hot water,
you're not wasting energy heating water when you don't need
it, such as when you're sleeping or not at home. This energy
savings translates to dollar savings for you and reduced impact
on our environment. Furthermore, since a tankless water heater
heats the water as you use it, you can have an endless supply
of hot water, provided you size the unit appropriately. Tankless
water heaters are also designed to last for 20 years and are
smaller than tank units.
How do they work?
When a hot water
tap is opened, the cold water enters the heater and triggers
the heating elements or burners to turn on. Your hot water tap
acts as an ignition key for the energy used to heat the hot
water you need. The water is then heated as it flows through
the heating elements or heat exchanger. As you change the water
flow, a water valve or thermostat controls the heating elements
or burner flame to maintain a constant temperature. The amount
of energy used is always proportional to the volume of hot water
being used. When the hot water tap is turned off, the system
The water temperature
can be adjusted to produce outlet temperatures ranging from
100° to 140° F.
How can a tankless water heater heat water instantly?
When you open a faucet, the flow of the water triggers the heater
to turn on. Whether you use gas or electricity, the powerful
gas burners or electrical elements will turn on, rapidly heating
the water as it passes through the unit. The water is heated
instantly, and the time it takes to obtain hot water is directly
related to the distance the hot water has to travel from the
water heater to where hot water is being used. The burners or
elements then shut down when you shut off the hot water. The
energy that is consumed is only for the hot water that is being
How much money can I save?
Depending on which model of tankless water heater you purchase,
and what size storage tank you have now, and if it runs on gas
or electricity, you could save anywhere from 11% to
69% off your hot water heating bill. How? Most homes
use hot water for a cumulative total of about one hour per day,
yet they typically keep 40 or 50 gallons (oftentimes more) of
water hot 24 hours a day. Having a system that eliminates the
storage and heats water only as you use it can dramatically
reduce your energy consumption.
Can it really provide an endless supply of hot water?
Yes. Because storage tank water heaters store a finite amount
of water, when that amount is used up your shower goes cold
and you have to wait for the heater to heat the water back up
(this is known as recovery time). Because a tankless water heater
heats the water as it passes through the heater, you can never
run out, provided flow limitations are not exceeded.
Are there other benefits of a tankless water heater?
There are many advantages of having a tankless water heater
in your home. Besides the money savings, endless hot water and
smaller impact on the environment, a tankless water heater:
- Is very small and can hang on the wall, thereby saving you
valuable floor space.
- Is designed with replaceable parts and is built with such
materials as copper, stainless steel, and aluminum (the AquaStar)
so as to last a lifetime. Energy savings is only one segment
of savings - with proper care this could be the only water
heater one needs in a lifetime.
- Is almost entirely recyclable, so if you ever decide to
replace it, it doesn't have to go to the landfill.
- Will not develop a corrosive leak like a storage tank water
heater, saving you from expensive water damage in your home.
Note: A tankless water heater can leak if it is exposed to
freezing temperatures or has a manufacturing defect.
- Maintains its efficiency throughout the lifetime of the
unit. Storage tank water heaters decrease in efficiency over
time due to mineral build-up inside the tank. This is due
to the fact that storage tank water heaters store hot water,
giving those minerals a chance to settle out and bake from
the heat onto the walls of the tank, and onto the heating
element in electrical models, thereby reducing heat transfer.
Will I still get the hot shower I'm used to now?
Yes, provided you buy the right tankless heater for you. Tankless
water heaters are able to function at a variety of temperatures
that you can choose, and can produce hot water at the same flow
rate as your standard single-headed shower provides now (since
1992 all showerheads are designed to deliver a maximum of 2.5
gallons per minute, as mandated by federal legislation).
Will one tankless water heater do my entire house?
Yes. You must choose the size model to suit your home's hot
water needs, which is based upon the maximum flow of hot water
you need at any one time. We sell tankless water heaters that
are capable of handling one shower at a time and others that
can sustain a maximum of two showers at a time.
What if I have very hard water?
Since tankless water heaters do not store hot water, minerals
do not have as much of a chance to settle onto the heater. Therefore,
you won't see the same corrosive or scale build-up problems
with tankless water heaters that you do with storage tank water
heaters. And it is fine to use a water softener with a tankless
water heater, if you choose.
What limitations do tankless water heaters have?
Because this type of water heater heats the water as you use
it, the volume of hot water that it can deliver is directly
correlated to the amount of its energy input. The bigger the
burners or heating elements in the unit, the higher the volume
of hot water that it can deliver. Today tankless water heaters
come in various sizes to suit most homes' needs. Even if you
need to be operating multiple showers at once, tankless water
heaters can keep up.
How do I properly size a tankless water heater for my home?
You need to choose the model that can deliver the volume of
hot water to meet your needs. The best method for sizing this
type of water heater is to know how many showers each model
can run simultaneously. We have models that can run either one
or two showers at a time. Our most popular sized model is the
one that delivers one shower at a time. (Remember, although
it will only deliver one shower at a time, it can do so endlessly,
shower after shower after shower.)
Can I fill a hot tub with a tankless water heater?
Yes. Because tankless water heaters provide an endless supply
of hot water, you can fill a tub of any size. It is only a question
of time, meaning that our larger units can fill a tub faster
than our smaller units. Keep in mind that some tubs draw water
at high flow rates, so it may be necessary to limit the flow
so that the tankless water heater can adequately heat the water
that is being called for.
Is this a new technology?
No. Europe, Asia and South America, where energy costs are more
expensive than here in the U.S., have been using tankless water
heaters for 75 years. Controlled Energy Corporation has been
selling and supporting tankless water heaters in the United
States since 1979. However, most Americans are just now learning
of this technology and its benefits.
What is a point-of-use water heater?
A point-of-use water heater is a very small water heater, tank
or tankless, that is designed to be installed at the point of
use, thereby eliminating a long pipe run. They are mostly sized
to supply hot water to one specific application, usually a sink.
These can be either a mini storage tank or a tankless water
heater. A common application is a remote sink, such as a bathroom
in an office building or a service station. The other sensible
application is for distant sinks in the home that typically
take too long to receive hot water.
What are the advantages of a point-of-use water heater?
Point-of-use water heaters are usually used for one of two reasons.
One is to supply hot water to a remote location that is not
served by a larger water heater. The other is to eliminate the
wait time for hot water you may have at a particular faucet.
Both offer the advantage of not having to wait for hot water.
You can install a point-of-use water heater right at the source,
e.g., under a sink. Therefore, when you turn on the faucet you
have hot water instantly available to you. This both eliminates
your wait for the hot water and saves water, our most valuable
resource, from being wasted down the drain as you wait for hot
water to arrive.
Can I use point-of-use water heaters for applications other
than a sink?
Yes. You can place a mini storage tank (see Ariston) in-line
with your main water heater. These are available in 2.5-gallon,
4-gallon and 6-gallon sizes. These provide you instant hot water
at your washing machine or dishwasher, for example, and by the
time you exhaust that supply, the main water heater that serves
these locations has caught up, so you have a continuous supply
of hot water.
Are your products difficult or expensive to install?
No, they are not difficult to install. The installation expense
depends on many factors. Although tankless water heaters are
"on" for only a small fraction of the day in most
home uses, when hot water is being called for they require a
lot of energy because they are heating water instantly. Because
of this, AquaStar (gas tankless water heaters) sometimes require
expansion of the vent pipe and PowerStar (electric tankless
water heaters) sometimes require the electrical service in the
home to be upgraded.
Can any plumber install your products?
Yes, they should, after all it is just another appliance. But
experience has shown us that many will not because, as they
say, they are not familiar with the unit. ProEnviro
Construction will work with the approved
plumber who is familiar with the tankless hot water system installation
that would meet your requirements.
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