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Hot Water Recirculating Pumps

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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.

This cool pump connects to your water line just above your water heater.  You will need an electrical outlet to be installed nearby.  Do not use an extension cord to power the pump.

This cool pump connects to your water line just above your water heater. You will need an electrical outlet to be installed nearby. Do not use an extension cord to power the pump.

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.


25 Responses to Hot Water Recirculating Pumps

  1. What is a better brand for a hot water circulating pump to my water heater. I want one that will safe me water and energy. Thank you and I will be waiting for your pront response.

  2. The best solution, in my opinion, is a loop system, a circulation pump at the water heater with a flow switch and interval timer such that if the timer senses flow to a hot water faucet for a short time (like 2 to 5 seconds, adjustable) it will activate the pump for long enough to heat the loop (adjustable time for varying conditions) and then turn off the pump because it isn't needed after the loop heats up. Turning on any hot water faucet for the minimum interval to start the pump and then turning it off until the loop heats up eliminates tricky timers and saves keeping the loop hot at all times. This system requires a complete loop in the hot water system that is preferably insulated; a backflow preventer; an expansion tank; a small circulation pump, preferably brass or stainless; timer or timers and a flow sensor. I use a differential pressure switch but a paddle type flow sensor would work. I also put a filter screen ahead of the backflow preventer to keep any debris out of the check valves. Luckily I found a perfect timer at an electronic surplus store that has a settable delay on make, settable on interval and settable re-cycle interval. I have it set for 2 seconds to start the pump, 2 minutes for the pump to run and 10 minutes null time before the pump will run again. The differential pressure switch is set so that the flow is moderate to cause it to switch so a deliberate turning on of a faucet is required to activate heating the loop.

  3. I recently installed a 80 gallon electric hot water heater and I am not getting hot water to faucets unless I turn on several faucets further from the faucet I need hot water. It is a pressure problem. Will a recirculation pump resolve this issue? .......my home is two story, 4500 square feet and I never had this problem with my previous 2- 40 gallon propane water heaters.

  4. Tim, if a bypass-type valve is used between the hot and cold water supply at a fixture so a recirc pump can provide immediate hot water to the fixture, it seems to me that the cold water supply pipe then becomes filled with hot water. If I want cold water to drink immediately after using the hot water, will I not get hot water when I turn on the cold water faucet?

      • Whoa. Maybe I don't understand, but if the hot water is recirculating through the cold line, the water in the cold line seems like it would be warm (maybe not hot). So wouldn't you have the inverse problem? IE you'd have to clear the "warm" water from the cold pipe before that water is cold?

  5. Currently rented a home that has this loop is there regualtions on how long it's suppose to take for hot water to hit the faucet. OR possible quick burns to not happen example turn hot water on and takes little time to get hot to avoid burns regulations for builders to allow a time to get water hot to reach faucet

  6. I have two hot water heaters in my attic side by side. Each supplies a different area of my house (one story). Do I need two recirculating hot water pumps or can I use one pump for both hot water heaters?

  7. I have a rennai tankless water heater. Is there a recirculating pump designed to help reduce the water wasted waiting for hot to get to the taps?

    • With tankless water heaters there is not a good recirculating pump. You would be able to waste less water, but you would be running the water heater so much more than normal (since supplying *any* hot water means the tankless heater is kicking on as opposed to having 50+ gallons in reserve.)

  8. I live in 1 story house build on a slab. Hot water to the bathrooms is not my problem. My kitchen and laundry room is at the end of the run. My dishwasher and washing machine don't run correctly because the demand water never gets "hor enough" Whirlpool refuses to acknowledge a problem because I don't meet their standard of 125 degrees within 20 seconds.
    Suggestions please.

  9. If the distance from HWH to a bathroom is large, what about using small point of use (~2-3 gallon) at the bathroom in line with the HW pipe?

  10. You stated that you found a "perfect timer at an electronic surplus store that has a settable delay on make, settable on interval and settable re-cycle interval. I have it set for 2 seconds to start the pump, 2 minutes for the pump to run and 10 minutes null time before the pump will run again."

    What is the make and model number? for I have been having a difficult time finding one.


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