For those of you who have not encountered one, an on demand hot water system is a hot water delivery system that uses a pump get your hot water from your water heater to your fixture quickly without wastefully running water down the drain.
Push button hot water
When you want hot water you press a button which turns on the pump, speeding hot water to you, while pumping the cooled off water in the piping back to the inlet of the water heater. It just pumps the water around in a big loop. When hot water reaches the pump it shuts off, preventing the cold water line from filling with hot water. At that point you have instant hot water when you turn on the tap. Several manufactures of these systems offer other methods than a button to turn on the pumps, such as motion detectors and photo cells.
Where is the best location for the pump?
Depending upon how your house is plumbed you may be able to cover a number of fixtures with just one pump. Most often the pump is placed at the fixture furthest from the water heater; however it’s not difficult to find the best location for the pump. To do so, go to the sink where you think the pump should be located, and turn on the hot fixture letting the water run until it is hot, then shut it off.
You have just simulated the operation of an on demand system. The difference is you ran water down the drain waiting for the hot, but the pump would not. Now if you go to another fixture and turn on the hot water, you will be able to tell it you get hot water more quickly than normal. You have to wait at least an hour between tests to let the piping cool off.
Save time and water
There are a number of benefits to having an on demand system in your home. With most installations you save time since you don’t have to wait quite as long as you would with a normal plumbing system. Better than that though is the water savings. In homes with long pipe runs to the most frequently used fixtures the water savings can be huge. Studies have shown that a family of four can save over 15,000 gallons of water per year.
You might get cleaner dishes. The number one complaint that dish washer manufacturers hear about from their customers is the dishes don’t get clean enough. According to the manufacturers the reason is nearly always the temperature of the water. If it is not hot enough it doesn’t completely dissolve the soap, and hence the dishes don’t get as clean. Before you it the run button on the dishwasher, hit the button.
If you are the kind of person who turns on the shower and then goes and does something else while waiting for the hot water to arrive, and comes back to find the water is hot, then you could save significant amounts of energy. Heating the water is far more expensive than paying for the water itself, so running heated water down the drain is expensive. An on demand pumping system eliminates this waste of energy.
If you have a septic system, then you know that reducing the amount of sewage entering the system is a good thing. Homes with septic systems often have a well to supply fresh water. If you have a well, you have a water pump. Reducing the amount of water being used by the system reduces the run time for the pump, reducing your energy usage and saving you money.
Demand systems use very little energy. Since the motor only runs for a few seconds at a time they typically use less than $1.00 per year in electricity. And since they don’t circulate hot water into the cold water line, they do not use more heat energy than a normal plumbing system.
If you have city water and sewage, then by reducing you water consumption you are reducing the amount of pumping and treating that must be done to the water supply, thus reducing energy usage and reducing the emission of greenhouse gases.
Makes tankless water heaters greener
If you happen to have a tankless water heater then you are probably aware that it takes even longer to get hot water with such a heater, and that of course, makes the on-demand system just that much more valuable. Although hot water circulating systems don’t work with tankless heaters, most of these systems do. Some do not have a high enough flow rate to turn on a tankless heater, so check with the manufacturer before making your purchase. The Chilipepper appliance will turn on any tankless heater.
Demand systems are pretty easy to install. The pumps connect between the hot and cold water lines, and with some systems such as the Chilipepper appliance you don’t even need to turn off the water main, just the two angle stops under the sink. You do need a 110 volt outlet to provide power to the pump. If you don’t want to mount a button, or if you want to be able to activate the system from another location, most pumps offer remote control, X-10 control, or wireless remote operation.
If you decide to install an on demand system in your home you should check with your water company, as many water suppliers are offering substantial rebates for these hot water systems.