Electric hot water recirc decom and confusion

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Sloanbj

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I have an electric 50 gal hot water tank. It serves three bedrooms and baths which are located up to maybe 50 feet away.

A previous owner installed a Grundfos recirculation pump to reduce the time to wait for hot water at the taps. I don't like the recirc pump for two reasons. First, it is noisy - not horrible but loud enough to hear in a quiet house at night, either from the basement hallway near the water heater or water gurgling in the bedroom walls upstairs. Second, the recirc loop triples the piping distance to the taps (if I understand it) so with the pump on, I actually get a cooler shower max temp than with it off!

I have unplugged the recirc pump. I am happy with this.

My question is - should I isolate and drain the water from the recirc loop? I have attached a photo of the water heater plumbing. There appears to be sufficient valvage to isolate and drain the loop. I assume I can close the valve right above the cold intake to the water heater, then drain the recirc loop with the hose bib on the upper right.

Any issue with that?

While we are at it, I'm not sure I even understand the recirc piping. Looks to me like all it does it recirc cold water through the walls before it goes into the water heater?? Maybe I am wrong and all this system does is pre-heat the intake water by circulating inside the house? If so, why do I get a cooler shower with the pump turned on?

Thanks for your thoughts.

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Twowaxhack

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Personally I would remove any unneeded piping, especially if it looked liked what’s in the pic.
 

GReynolds929

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That definitely could be piped more efficiently. Looks like its missing a check valve on the cold line.
 

MicEd69

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According to your picture, your Grundfos is installed on the cold water inlet to the water heater, taking suction from the small copper recirculating line. The proper installation for that Grundfos pump is for it to take suction from the full sized hot-water outlet line, with the recirculating line returning the unused hot water to the cold water inlet of the water heater. The arrangement you have could be causing suction head issues with the Grundfos pump, which could be causing your noise problem. It could also explain why when the pump is operating, your shower is not as hot as it is when the pump is off. The pump is now pulling hot water from the hot water line, thereby reducing the amount of hot water going to your shower.

If you install it correctly, it should work fine. Installing a timer on the pump will also reduce electricity in the off-use hours. If nobody is home during the day, why circulate that water. And should you need to take a shower at 2:00AM, you would simply need to wait for the hot water to make it to the shower.
 

TomFOhio

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Is this the system that you have?? Do you have that plastic device under your farthest sink upstairs? This is exactly what MicEd was
talking about. It goes into the hot side of the water heater and it has a built in timer to run when you want it to. The ones that I
have installed were not loud.
 

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MicEd69

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Sloanbj described "recirculating loop" piping, and the pictures show small copper tubing in that mess which I assume is it. It looks like the original owner didn't use the "crossover" valve as you have, but apparently installed a separate small copper line, I assume, which should connect to the farthest hot water faucet. So apparently their "design" was for the pump to take suction from that copper tubing and pump it back into the water heater cold inlet. The pump could be installed on the hot water outlet and use the existing "recirculating loop" tubing to return the unused hot water into the water heater cold inlet. But using the "crossover" valve you show is really the best way to go as that is the actual design for this pump. And with the timer, you are saving energy when "instant" hot water is not required.
 
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GReynolds929

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He has a dedicated return loop plumbed in. Looks like two returns actually. This is not the home comfort system, which is a retrofit system for homes that don’t have a dedicated return line. His pump is for dedicated returns and has no timer, it is always on. We like to pipe them to return through the drain valve into the bottom of the tank. That way you dont need a second check valve on the cold supply.
 

Sloanbj

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Thanks for the replies, everyone.

To clarify - my Grundfos U15 pump is similar to what someone posted but does not have the timer. I can install a timer or smart plug on the wall plug, if needed, but that's not my main issue.

So, my pump is sucking from both the two small copper lines (coming out of the wall0 which we must assume are a dedicated return loop to the farthest bathroom. They pull hot water around from there and send it into the cold inlet to the water heater. My impression is that the distance of the copper piping means the water never stays hot after a full return trip, so the pump runs all the time even when I put on the Grundfos aquastat (black wire coming out of Grundfos - temporary setup). I get warmer water sooner when the pump is on, but never get hottest water since the pump is stealing some hot water volume all the time.

Also not sure why the pump is noisy.

With the pump off, I assume I should just close the isolation valves (silver handle valve between return loops and red handle valve on top of pump). I have no idea why they added the drain valve to the far side. I guess I could open than and do some water temp measurements with the pump running?

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Twowaxhack

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I’d recommend replacing all the galvanized piping. Correcting any original piping errors in the process.
 

MicEd69

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See my earlier post. Taking suction from those small copper tubes could be causing NPSH problems for the pump. That could explain the noise from the pump. Does the noise sound like there is gravel in the pump? The proper installation takes suction from the hot water outlet and pumps that hot water through the circulation piping. Trying to pull cold water from far away isn't the correct way for that pump tyo operate.
 

Sloanbj

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The noise does not sound like gravel. It is just a normal motor hum but is loud enough to be heard outside the basement utility room (with the door shut) and even upstairs.
 

Twowaxhack

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The noise does not sound like gravel. It is just a normal motor hum but is loud enough to be heard outside the basement utility room (with the door shut) and even upstairs.
Your piping is not proper. That pretty much sums it up.
 

Twowaxhack

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The pump doesn’t have to be mounted on the hot water outlet of the water heater. That’s pure fiction.
 

MicEd69

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The "theory" used for the "classic" installation of the Grundfos U15 pump is on the hot water outlet of the water heater. (See the picture below.) That would imply, and would seem reasonable, that the vast majority of the Grundfos U15 pump installations are so installed. However, the pump can be installed in other locations in the recirculation system.

The concern in this particular installation is the layout of the recirculating system and the amount of smaller copper tubing that is part of the recirculation piping. That smaller tubing will increase frictional pressure drop on the suction side of a pump which can cause operational problems. Installing this pump on the hot water outlet and using the crossover valve that TomFOhio indicated thereby decommissioning the recirculating piping, which appear to be in part galvanized, would provide a better and proven system. As the recirculation piping is galvanized, is some or all of the house piped with galvanized piping?

Re: the noisy pump, how old is it? It could be that the pump has been damaged or is worn out.

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arctic bill

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they way we do a circulation hot water line . at the farthest end of the hot water line just before the last faucet we install a tee on the hot water line and a valve then run the recirc line all the way back to the hot water tank , then a check valve and a pump where is connect to the cold going into the hot water tank .
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Sloanbj

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MicEd - I don't even understand that setup. The pump pushes hot water into the hot piping and then what? How does it get back?

The Arctic Bill configuration at least has a return line/loop. It looks as though it would send warm water to the cold taps when they are correct? That may not be desired.

The galvanized pipes are great, huh? Makes me wonder if the recirc loop was installed with the rest of the pluming in 1972.
 
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breplum

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O.P., sorry, you don't understand the picture from arctic bill. (btw, water heaters do not have cold on the left, as illustration lamely displays)
Before I start, let me say: Properly installed Grundfos and other similar fractional h.p. circulators are nearly silent. We pretty much have to use other tricks to even tell that the pump is running, b/c they are always warm/hot to the touch even when locked up.
Drawing shows a check valve on the cold, causing flow in direction of the blue arrows, into the cold side. There is a dip tube on the cold side which puts the returning water in to the bottom of the tank.
For the record, recirculation systems should always utilize sweep 90s for erosion prevention.
 

Sloanbj

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BREplum thanks for pointing that out - so the Arctic Bill drawing is basically what is shown in my setup except I have two return lines instead of one. They feed into the pump which then sends the water to the cold inlet to the water heater.

I agree erosion is a concern and sweeps are best.
 
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