Weird hot water circulator situation

[Gene Ressler]

Hi all. A year ago we bought the house of our dreams. 14 years old, 4br, 2 stories + attic. The inspection report noted the pressure relief on the hot water heater was bleeding. The expansion tank was full. Replaced that, and all has been well.

While doing this I noticed there's a Grundfos circulator pump sitting on top of the water heater. Totally dead.

It's a year later, and we'd like to get the circulator system working.

Here's the weird part. There does not appear to be a dedicated return line: water heater has cold in and hot out. Nothing else. The pump is plumbed as though there's a cold/hot bypass valve. But for the life of me I can't find a bypass valve under any sink in the entire house. Been through them all three times now.

So what do I do?

I figure if I just replace the pump and there's no bypass, it won't work and will quickly burn out. But I don't want the work and $$$ for bypasses if they're not needed. Is there some way I can figure out if there's a bypass hiding somewhere I can't find it?

All advice deeply appreciated.

Fwiw, here is what the pump looks like. I can't even find a SKU for it. There's no number on it that I can see. It's a long discontinued model.

All help deeply appreciated

Cheers,
Gene

 

[Jadnashua]

97525921 - Grundfos 97525921 - UP10-16BN5/ATLC, 1/2" Female NPT, 115V Pump, w/ Timer and Aquastat (supplyhouse.com)

This is listed as a direct replacement. The one you have was discontinued in 2012.

 

[Sponsor]

 

[Jeff H Young]

you could shut water off to house and disconnect hot at water heater and connect water to the hot line pressurize it. then open a cold line a hose bib will work if water flows out then the recirc should work.
kinda hard to describe a very basic concept . No Idea how they piped it but would assume replacing a bad pump should fix it but if you want to take the time to figure it out and even then you'll never know how its going to work till you try it out. Your time is free but a pump isn't and Id hate to put a pump on just find out it didn't work. but I've replaced burned out pumps circ pumps not knowing how its going to work before.

 

[Gene Ressler]

you could shut water off to house and disconnect hot at water heater and connect water to the hot line pressurize it. then open a cold line a hose bib will work if water flows out then the recirc should work.
kinda hard to describe a very basic concept . No Idea how they piped it but would assume replaceing a bad pump should fix it but if you want to take the time to figure it out and even then youll never know how its going to work till you try it out. Your time is free but a pump isnt and Id hate to put a pump on just find out it didnt work. but Ive replaced burned out pumps circ pumps not knowing how its going to work befor.

Thanks for that. I'll try something like you suggest. I'm thinking that maybe the pump stopped working and then renovation was done where the bypass valve was removed and not replaced because the circulator was broken anyway.

 

[Jeff H Young]

Thanks for that. I'll try something like you suggest. I'm thinking that maybe the pump stopped working and then renovation was done where the bypass valve was removed and not replaced because the circulator was broken anyway.

anything possible it might not be workable system

 

[Gene Ressler]

97525921 - Grundfos 97525921 - UP10-16BN5/ATLC, 1/2" Female NPT, 115V Pump, w/ Timer and Aquastat (supplyhouse.com)

This is listed as a direct replacement. The one you have was discontinued in 2012.

Hey thanks. Yeah I knew it wasn't made any more. I just wish they'd kept the 1 1/4" union connection rather than switching to NTP. I'll need new fittings and repiping. Argh...

 

[Bannerman]

If there is no circulation return line, how is the pump plumbed?

While a circulation pump will usually be plumbed into the return line close to where the water is flowing back into the bottom of the WH, some place the pump in the hot water line exiting the WH, so hot water will be pushed by the pump through the system.

When the home is not equipped with a dedicated return line, often the cold water piping will be utilized as a hybrid circulation system. When the cold piping is used as the hot water return, a thermostatic crossover valve will be utilized to stop circulation when hot water is sensed at the crossover valve, to prevent the cold piping from filling with excessively hot water. The crossover valve will be typically located under the sink that is the furthest distance from the WH.

https://www.supplyhouse.com/Grundfos-595926-Comfort-Valve

As you have been unsucessful locating a crossover valve, look for an access panel behind a shower or other fixture. If there is an access panel or removable apron below the bathtub, a crossover valve could be located there.

Since you are in California, a basement seems unlikely. If your plumbing lines to each fixture are routed through the attic, a crossover valve maybe located in the attic.

 

[Jeff H Young]

OP seems to think that someone installed a pump without the crossover. and that it has never worked . but now the pump is burned out and doesn't want to spend money on a pump that won't do anything. that's why I gave him some pointers on diagnosing

 

[Gene Ressler]

anything possible it might not be workable system

Thanks again. I think I have an idea how to do it pretty easily.

• Turn off the house water main valve as you said and also the cold water inlet valve at the water heater.
• Instead of disconnecting the heater, hook up a hose on the heater's drain bib. I can use the outdoor hose bib that stays on when the house is off.
• Open a cold water faucet. There's a sink right in the heater area.
• Let a little pressure into the heater with the drain bib valve.
• See if anything comes out of the cold faucet.

Does that sound right?

 

[Jeff H Young]

Thanks again. I think I have an idea how to do it pretty easily.

• Turn off the house water main valve as you said and also the cold water inlet valve at the water heater.
• Instead of disconnecting the heater, hook up a hose on the heater's drain bib. I can use the outdoor hose bib that stays on when the house is off.
• Open a cold water faucet. There's a sink right in the heater area.
• Let a little pressure into the heater with the drain bib valve.
• See if anything comes out of the cold faucet.

Does that sound right?

yes that's an easy way to test, I would get a lot of water out first to determine if water is crossing from hot to cold