Hot Water Recirculating Pumps
DEAR TIM: It takes about 30 seconds for hot water to reach my shower each morning. It is frustrating to wait that long. Is it possible to have hot water within a second or two after I turn on the valve? I have seen different recirculating systems that promise hot water instantly and they talk about huge energy and water savings. Is this true? Is there a way to get hot water using simple gravity instead of a pump? Chad G., Birmingham, AL
DEAR CHAD: Many people wait for hot water just as you do each morning. A similar thing happens when people operate other sinks, dishwashers and washing machines. Fortunately, this problem can be solved one of two ways depending upon how your plumbing system is designed. Keep in mind that the work to achieve your goal is not something the average do-it-yourselfer can tackle. What's more, certain cities and states have strict regulations with respect to modifications made to water supply systems that are connected to public water systems. Be sure to call your local plumbing inspector before you cut into your piping system.
Clean water is a valuable natural resource and it should not be wasted. The trouble is, in many localities, water is a very cheap commodity. When prices are low, people tend to waste. For example, a cubic foot of water costs me just a little over 1.6 cents. There is a very good possibility that you waste less than a tenth of a cubic foot of water each morning. To prove this, assume that there is 25 linear feet of three quarter inch piping between your shower faucet and water heater. Do the math and you will find out that there is just .076 cubic feet of water inside the water pipe. To waste one dollar's worth of water, one would have to take over 800 showers.
To get instant hot water as you often find at hotels and other institutions, you need to have a loop in the piping system that circulates hot water back to the water heater. Most houses do not have a loop as the hot water pipe typically dead ends at the plumbing fixture that is farthest away from the heater. It is possible to install an effective return loop in single story houses that have a basement or crawl space where the water supply pipes are visible below the floor joists. Two story houses make this task nearly impossible, as the piping system is typically hidden in the walls of the home.
But, you don't have to install a return loop if you choose to use a modern recirculating pump system. These products employ a nifty temperature actuated by-pass valve that connects the cold and hot water supply lines at the fixture that is farthest away from the water heater. The bypass valve uses the cold water line as the return loop back to the water heater.
Not all recirculating pump systems are the same. One system places the pump under the sink at the farthest fixture. You have to push a button to start the pump. The trouble with this system is that you still have to wait for hot water. What's more, this pump needs high voltage electric to operate. It can be a huge challenge to install an outlet under a sink.
Another system activates a remote pump that can be near the water heater. The trouble with this system is that it pumps water through the system whenever the temperature drops at the activation valve. This system wastes energy dollars as it pumps hot water while you sleep and are away.
Perhaps the best pump system is one that has a temperature controlled by-pass valve under the farthest fixture sink and a timer on a pump that can be conveniently located adjacent to the water heater. The timer can be set to go on and off at 15 minute intervals depending upon when you feel you need hot water at the fixtures. The pump is equipped with a handy extension cord that can be plugged into a convenience outlet near the pump. There is no water waste with this pump and it also minimizes energy waste since it only sends hot water into the water supply lines during the programmed times.
Gravity hot water recirculating loops that do not require a pump can sometimes be installed after a house is built. They will only work when the water heater is below the water supply lines. This system requires that the hot water line return back to the heater after it services the farthest fixture. The return line connects to the bottom of the water heater at the drain valve. Natural convection drives the system. Energy loss is a minimum if you insulate the entire hot water loop except for the last 15 feet of pipe as it re-enters the water heater.