Recirculating Pump Installation

[dwaun]

Hello! I'm adding a recirculating pump to my residential hot water system to reduce the wait time for hot water. I was able to run a return line from the furthest fixture back to the hot water heater. I plan to put the pump and a one way valve on the return line near the tank, but I'm not sure if I need to return the water into the bottom of the tank or if it can be tied to the tank's cold water supply line.

Connecting the return line to the cold water supply would be easier in my situation, but some places suggest that you must bring the return into the bottom of the tank by removing the drain. Does anyone know if that's required and if so, why?

Regards,
dwaun

 

[Bcarlson78248]

I've looked at various diagrams for recirculating systems, and I think the answer to your question depends on where you have one-way valves installed, and how you determine when to turn off the pump.

I don't know the real answer, but this is my educated guess for why they want you to connect to the bottom of the tank. If the system just runs continuously or has a simple timer for set periods, once you get hot water coming back in the return pipe you would be returning hot water to the cold water line into the water heater. It may then feed hot water back up into the cold water pipe (instead of down into the water heater) when someone turns on a cold water tap. I think you could fix this with a backflow preventer where the incoming cold line connects to the water heater or you could have a temp sensor that shuts the pump down as soon as you start getting hot water in the return line at the pump. If you instead decide to connect the return line to the bottom of the tank there is no issue because its returning water directly to the hottest part of the tank.

Bruce

 

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[Phog]

Hi dwaun, it is common to have recirculation return lines teed to the cold inlet, unless there is a separate connection on your tank available for the purpose (some more expensive tanks are equipped with a pair of hot/cold side connections for hydronic heat, which can also then be utilized for recirculation).

Anything coming in through the main cold water inlet connection already travels down through the dip tube to be deposited into the bottom of the tank, which would include your teed recirculation return water. So you are not really gaining anything by going in through the drain.

Some people do hook the return up to the drain as you describe, but I view this as unnecessary. If you do go that route, make sure to at least keep the drain valve on a tee so that you can flush the tank periodically. Don't just completely remove the drain.

 

[dwaun]

I've looked at various diagrams for recirculating systems, and I think the answer to your question depends on where you have one-way valves installed, and how you determine when to turn off the pump.

I don't know the real answer, but this is my educated guess for why they want you to connect to the bottom of the tank. If the system just runs continuously or has a simple timer for set periods, once you get hot water coming back in the return pipe you would be returning hot water to the cold water line into the water heater. It may then feed hot water back up into the cold water pipe (instead of down into the water heater) when someone turns on a cold water tap. I think you could fix this with a backflow preventer where the incoming cold line connects to the water heater or you could have a temp sensor that shuts the pump down as soon as you start getting hot water in the return line at the pump. If you instead decide to connect the return line to the bottom of the tank there is no issue because its returning water directly to the hottest part of the tank.

Bruce

Thanks for your thoughts, Bruce. I understand the need for a one way valve on the recirculating return line. My last house didn't have one and I found myself getting cold water from the bottom of the tank after a short amount of use. But, I was wondering if it's acceptable to put a one way valve on the incoming cold water supply line. Does the hot water heater need to be able to push water back on the cold water supply for expansion? None of my houses have ever had an expansion tank, but I assume that's because they can push back on the cold water supply if needed. Is that what happens???

 

[Jadnashua]

If you have a tempering valve and it has a port for the recycling, return it there for it to work well. Otherwise, you can run it to the drain. Because no new water is coming in when recycling and a tempering valve, there's no new fresh cold water to temper the outlet of the tempering valve. A tempering valve with that recycling port will mix the return water with the hot outlet and still keep the max temp at the tempering valve's setting.

 

[Baby j man]

Hello! I'm adding a recirculating pump to my residential hot water system to reduce the wait time for hot water. I was able to run a return line from the furthest fixture back to the hot water heater. I plan to put the pump and a one way valve on the return line near the tank, but I'm not sure if I need to return the water into the bottom of the tank or if it can be tied to the tank's cold water supply line.

Connecting the return line to the cold water supply would be easier in my situation, but some places suggest that you must bring the return into the bottom of the tank by removing the drain. Does anyone know if that's required and if so, why?

Regards,
dwaun

Tie it into the cold water line and use two check valves . One on the cold so you don’t get recirc water going into the cold line and one check valve on you’re recirc line so you don’t get cold mixing with the recirc line going to the hot line

 

[hj]

If you do use two check valves, you WILL have to install an expansion tank to absorb the pressure caused by heating the water.