Be Green, Save Water, Time, Energy and Stop Running Water Down the Drain!
We would like to be green. But we all do it. Run water down the drain while waiting for hot water. It’s not exactly water conservation, but who is going to jump into the shower when the water is freezing cold! Well no one. Is there a way to be green and avoid wasting all that water by running it down the drain?
Yes. A hot water circulating system will eliminate the need to run that water down the drain. There are several types of hot water circulating systems available, and they are fairly easy to understand.
Full time hot water circulating systems provide for water conservation but do not save energy!
The first type of system is the full-time circulating system. In this type of system the hot water outlet of the water heater connects to a pipe that runs past each fixture in the home, and then back to the water heater. A small pump circulates the hot water through the pipe, thus there is always hot water near every fixture. Instant hot water!
But there is a price to pay! This is an expensive system to operate, since the pump consumes some energy and is running constantly; you have to pay for that energy. But far greater is the expense of heating the water. Heating water is very expensive, and so when you pump it through a long pipe, and the pipe is losing heat energy to the atmosphere around it, you end up spending a lot of money to heat the hot water piping and its immediate surroundings.
You can place the pump on a timer, so that during periods that people don’t normally use hot water, the pump is turned off. That helps, but it is still very expensive. Some systems also control the pump by monitoring the temperature of the water. The pump turns off when it reaches a set point, and then back on when the water drops to the lower set point. This reduces the energy consumption by the pump, but does little to reduce the far larger energy losses of the heat loss from the system.
A dedicated return line is needed
Another problem with these systems is that they require a dedicated return line from the furthest fixture back to the water heater to function. This is an expensive option when building a home, and a far more expensive option to add on to an existing home.
Cold water return type recirc systems
There is another class of hot water circulating systems, sometimes called recirc systems, that do not require a return line. These systems use the cold water line as the return line. The cold water line always connects to the inlet of the water heater, so it will always work. There are a number of approaches being used for these cold water return type hot water circulating systems.
Thermo siphon hot water circulating systems
In some instances, for instance, where the water heater is lower than the rest of the system like in homes with a basement, a gravity type, or thermo siphon type system can be used. Since hot water is less dense than cold water, the hot water rises up from the water heater to the fixtures and the cooled off hot water goes down the cold water return line back to the heater.
A connection is required between the hot and cold water lines, and a valve that responds to temperatures is installed between them. Without a valve, the hot and cold water would always mix when you used either one.
Warm water circulating systems
Some systems use a pump connected between the hot and cold water lines with a built in valve, and as with the full time systems, some are operated via a timer, some are temperature controlled, and some use both methods. They are set to turn off at around 85 to 90 F. They can’t circulate hot water because that would keep the cold water lines full of hot water.
These systems get you hot water faster, since the pipe is not cold when you turn on the hot water faucet and thus absorbs less heat from the hot water as it travels to the fixture. However, you must be able to live with less than cold water in your cold water pipes.
This system also wastes energy keeping the hot and cold water pipes warm. It does provide some water conservation, although you still run water down the drain if you wait for hot water as opposed to luke warm water.
You will save water, but you won’t really be green with this system.
Hot water demand systems save water, no water gets run down the drain
Another type of system is known as a “hot water demand system”. With the demand type system, the user must push a button or utilize some other signal to start the pump, and then when hot water reaches the fixture, the pump shuts off.
The demand system is the lowest cost in terms of operating costs since it does not cause any more heat loss than if you just used the hot water fixture without the system. It only pumps when you “demand” hot water. Typically such systems use only $1 to $2 per year in electricity for running the pump.
You obtain your hot water more quickly than if you ran the faucet full blast, and you don’t wastefully run water down the drain. You’re happy and the environment is happy! With a demand hot water system you are finally able to be green.