Hot water recirculating pump with PEX manifold

[Kevin121]

My home's plumbing system uses PEX with a "home run" type PEX manifold. The cold water supply runs from the manifold to the inlet of the water heater. The hot water outlet from the water heater first runs (back) to the manifold and then out to each hot water faucet in the house. The furthest faucet from the water heater and manifold is about 75 feet away is the Kitchen sink. Right now it takes about a minute and a half of running (cold) water out of the hot water tap until it runs warm so I am looking into some type of recirculation pump that will provide more instant hot water at this particular faucet (the other faucets in the house are much closer to the water heater and manifold). I am looking at these point of use recirculation pumps that feed hot water into the cold side (thermal bypass valve) and doesn't require a return line back to the water heater:

(https://www.amazon.com/replaces-Grundfos-99452459-UP15-10SU7P-Recirculation/dp/B07PY4S16Y/ref=sr_1_8?crid=2VXCVZJS77XNT&dchild=1&keywords=hot+water+recirculating+pump&qid=1617104673&sprefix=hot+water+reci,garden,150&sr=8-8).

I had intended on installing the pump on the outlet 3/4" PEX line of the water heater but then I didn't take into consideration the hot water return line from the water heater goes back to the manifold first, and then out to all the faucets in the house on their own "home run" lines. I wasn't sure if this would present an issue as I only am concerned with getting hot water (quicker) to the farthest faucet located in the kitchen.

If placing the pump before the manifold presents an issue, then is it possible to install the pump inline after the manifold on the supply line leading directly to the kitchen faucet? The faucet supply lines are all 1/2" PEX so I didn't know if that would present an issue for the pump. Thanks in advance.

 

[Tuttles Revenge]

The pump you listed would work. I believe that manifolds have limitations on constant hot water recirculation. But If the recirc were only momentary, switch activated either manually or with an aquastat, it shouldn't be an issue. with that setup, you will be pumping warm water into your cold water pipe.. so you get a bit of mixed water there.

 

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[Kevin121]

Thanks for the feedback, I was reading some comments online about this not being effective for plumbing systems with a manifold so I wanted to get clarification from this group. So installing the pump at the water heater (before flowing back to the manifold) would work ok in this case, and then have the thermal bypass valve installed at the kitchen faucet location? The only place I would expect to see some initial warm water in the cold pipe would be at the Kitchen?

Alternatively if it's better to install the pump on the home run between the manifold and the kitchen faucet I would be fine to do that as long as the 1/2" pipe is not an issue for the pump.

Also wanted to point out that my water heater apparently has heat traps in it, so I didn't know if that would present an issue for this system?

 

[Tuttles Revenge]

No recirculation system is effective in a system with a manifold... insomuch as it will only get hot water to one single location... so as long as you understand the limitation, then your expectation is set.

The pump you posted is designed to attatch directly to the top of the hot nipple on the tank. It pumps water in the direction of flow to the bypass valve, I can't imagine that a heat trap would affect that.. unless it creates too much resistance.. doubtful it would.

 

[wwhitney]

Seems like a pump under the kitchen sink would be simpler. They make point of use pumps to be installed at the end of line, then you don't need the separate bypass. I suggest an on demand version where you push a button or trip a motion sensor and it runs.

Cheers, Wayne

 

[Kevin121]

No recirculation system is effective in a system with a manifold... insomuch as it will only get hot water to one single location... so as long as you understand the limitation, then your expectation is set.

The pump you posted is designed to attach directly to the top of the hot nipple on the tank. It pumps water in the direction of flow to the bypass valve, I can't imagine that a heat trap would affect that.. unless it creates too much resistance.. doubtful it would.

I am only looking to speed up hot water to my most distant faucet in the kitchen so that would be where the bypass is installed. The other faucets in the house are located much closer to the water heater and manifold and they currently get hot water much faster. I'm just trying to understand whether this will be effective for my situation and whether it's worth installing? It sounds like you're saying this system is not effective with having the manifold in place, I'm trying to understand why that is?

Alternatively - Is is possible to mount this type of pump after the manifold on the line running directly to the kitchen faucet with the 1/2" PEX supply line?

 

[Kevin121]

Also I am not opposed to installing a return line from the hot supply of the kitchen faucet back to the water heater and make it true recirculation. In fact this method seems more efficient, rather then pumping hot water into the cold line. I have access in the basement to run a return line up under the kitchen sink. I assume I would need a Tee fitting at the kitchen faucet Hot supply, run 1/2" insulated PEX in the basement back to the water heater and then tie in the pump into this return line (i.e. Grundfos UP10-16) before running into the bottom of the tank where the drain valve is located.

I see some of these pumps have internal check valves built in, but if I purchased one without a built in valve, what side of the pump should the check value be placed (downstream closer to the WH, or before the return line gets to the pump (upstream)? What type of check valve would be recommended for this? Does the existing drain valve on the water heater need to be removed and install a Tee fitting to connect in both the return line and still have a drain valve? Other things I am missing or not considering? Thanks again!

 

[Jeff H Young]

where the pump goes shouldn't matter and if you run a return from k/s to w/h it's even better. so there you go personally I'd put pump at the w/h if I had a circ line but there may be other considerations

 

[mattTHEbastard]

Also I am not opposed to installing a return line from the hot supply of the kitchen faucet back to the water heater and make it true recirculation. In fact this method seems more efficient, rather then pumping hot water into the cold line. I have access in the basement to run a return line up under the kitchen sink. I assume I would need a Tee fitting at the kitchen faucet Hot supply, run 1/2" insulated PEX in the basement back to the water heater and then tie in the pump into this return line (i.e. Grundfos UP10-16) before running into the bottom of the tank where the drain valve is located.

I see some of these pumps have internal check valves built in, but if I purchased one without a built in valve, what side of the pump should the check value be placed (downstream closer to the WH, or before the return line gets to the pump (upstream)? What type of check valve would be recommended for this? Does the existing drain valve on the water heater need to be removed and install a Tee fitting to connect in both the return line and still have a drain valve? Other things I am missing or not considering? Thanks again!

Did you set up your system yet and if so, what route did you take and what is your opinion now? I have almost exactly the same issue/plan but I have a second line to most locations due to ambitious use of PEX. I hoped to use one line at the furthest outlet of the manifold as the recirculation line but maybe a couple of the extras could be placed into one recirc network before returning to the cold intake line of the gas water heater.

also I read about check valves and air purge or some such device. any required parts for this would be of great assistance thanks, hoping you or others have an answer to your already asked questions by now, haha thanks