Grundfos comfort system recirculation pump

www.yoursupplystop.com/…/Ch3eBw3_EAQYAiABEgIXOfD_BwE

I’m excerpting this from a recent thread. It was suggested as a retrofit solution to long wait times for hot water. It looks like a good thing. Has anyone used it before? Are there issues with back-pressuring the cold water supply system with water from the hot water lines?

jimhillra

in General Discussion 2 years and 6 months ago

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workisfun | 2 years and 5 months ago

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We installed a similar piece but still had to wait a while for hot, so we put in a dedicated hot water return, which solved it.

nyc_sport | 2 years and 5 months ago

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I have this in my apartment, installed by Eman several years ago. It works quite well. The bypass valves at the distant sink that allows the hot water to bypass into the cold water line is a plastic piece of crap and can leak, so keep an eye on it. Generally speaking, you put this bypass on the furthest fixture that has a hot and cold shut off, but you could put a bypass on multiple fixtures if they are on different branches. The water pressure in my apartment is already quite strong, and this creates no issue, other than as noted the warm water in the cold tap, but ours is on a powder room sink so that does not really present any issue.

brooklyndempsey | 2 years and 6 months ago

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I have a retrofit system like this installed in our summer house, as well as a standard recirculation system with return pipes in our brownstone–so familiar with both. We haven’t had any issues with the retrofit system, which has been running for years. Our timer setup is simple–set to run regularly during the day and off overnight.

As Lurker mentions the system will push some warm water into the cold line, so the cold tap will often start with lukewarm water. That takes some getting used to, but at least for us we got used to this quirk and let the water run a few seconds if we want cold water. Maybe a personal question if you’ll find this acceptable.

Having a recirculation system with a return pipe is certainly better–but not an option if the return pipe isn’t installed.

jimhillra | 2 years and 6 months ago

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Thanks. You can email me at jim(at)urban-pioneering.com.

In rowhouse-size buildings, the toilets are usually branched off the same riser as the sink, so there’s probably a few feet of branch piping between it and the riser. I expect it would get some of the warm water.

Lurker | 2 years and 6 months ago

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Mine didn’t have NPT connections–it uses the flexible connectors for all 4 connections, but has the same timer.
Good question about the toilet–I would imagine it depends a lot on how the bathroom is piped, whether the toilet is before after or parallel to the sink line. That said having warm water could actually be good because then you don’t get condensate on the toilet tank. Let me know how best to contact you Jim and I’ll send photo and you can decide.

jimhillra | 2 years and 6 months ago

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Lurker, thanks for the input. Hopefully, this is a better link: https://bit.ly/3NLp1fH, but it sounds like you were using a similar system, if not the very same. Let me know if it was. If we decide to go ahead with it, I just might take you up on that 50% offer!

The issue with the warm cold water was exactly what I was thinking might happen. I assume it also goes for other fixtures, like toilets. I wonder if there are any issues related to warm water in toilet tanks?

The instructions do go into a description of scheduling the pump, which might alleviate the issue, but only if you stick to that routine.

I also wonder about adding pressure into the system, as the pump would need to generate more pressure than the cold water supply. Would that added pressure create problems for valves, connections, or the cold water input for the HWH?

I’ve sent the info to a plumber to get his take on it, and will respond if he has any more salient points.

Lurker | 2 years and 6 months ago

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Your link is abbreviated so I’m unsure which model you were linking.
If you are doing a new install of a bathroom/kitchen and are able to pipe a return hot water line back to your hot water tank, that’s ideal.
Otherwise, you will encounter what we had when installing a water circulator at the sink, which is that the hot water goes down the cold line in a loop, and so should you turn on the cold water after it has circulated you will be getting lukewarm or even hot water which we actually found irksome–if it’s night time and you go to drink a glass of water it’s an unpleasant surprise. But no issues with pressure at all in my experience–the hot water is pushing the cold water in a loop.

You could probably manage it well by scheduling it to only circulate at the time when you shower kind of thing, but we didn’t get that far and ended up removing the system altogether as it didn’t work with our usage patterns.
Happy to sell you mine half price if you want to give it a shot!