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Strange Problem with Hot-Water Recirculating System

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AidanDanner

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I'm totally stumped here, hoping someone can help. When we moved into our 1954-construction home about ten years ago, we had a copper re-pipe done, and also a hot-water re-circulation system installed. It's been working great, until about six months ago, when I began to notice that the water coming out of our master bathroom sink (which is the sink located farthest from our conventional storage-tank water heater) was taking a long time to get hot. Well, I figured it's gotta be the pump, right? So I bought a new one, nearly identical to the old (a Grundfos UP15-29SU) and successfully installed it. I was very proud of myself, because I know NOTHING about plumping.

Well imagine my surprise when that DID NOTHING. The water STILL takes a really long time to get hot. The old Grundfos pump was probably just fine. Something else is going on. But what in the world could it be???

Below is a pic of the heart of the system. Pump is brand-new, pump timer is old (repurposed off the original pump), water heater's from 2009:

20200628_191556.jpg
 

Geofd

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It’s possible that the ( check valve) the fitting to the right of the pump is not working, you can inspect it by unscrewing the big nut on top make sure it’s clean of debris and opens and closes easily
 

Geofd

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Did you check the pump timer make it so it runs constantly and see what happens
Is the pump getting warm or is it hotter than normal
 

Jeff Handy

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Yes, stuck check valve was my first thought.
Feel the copper pipe down by where it enters the lower end of the water heater.
Is it hot?

Also, sometimes a new pump needs help to start spinning the first time after install.
I think you can remove that black slotted cap in the center, and there is a shaft that you can spin manually, if it is not already spinning.
Sometimes the pump feels like it is running but is actually jammed.

I forget if the shaft end has a screwdriver slot or Allen wrench hole that you can insert a tool into to manually give it a few turns, while power is off.

Turn the power off to the pump before trying to spin the shaft, then turn power back on.

Also, you can verify the pump has power going to it with a non contact voltage tester.

As mentioned, the breaker might be tripped.
It might be a gfci breaker, which needs the RESET button pushed to click back on.
And/or the breaker handle has to be pushed all the way to OFF, then pushed firmly to ON.

Some pumps also have a low, med, high speed adjustment lever.
 

havasu

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Flip the tab to on, and if it begins to get warm, it's working. If not, the pump is bad or your power is dead at the plug.
 

Jeff Handy

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PS, I think you will have to turn off the main house water, turn off the pump, turn off the heater, and drain the whole system from the drain valve near the bottom of the heater, before you can open up and inspect inside the check valve.

But others here can verify that.
 

AidanDanner

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Thanks for all these suggestions/advice! I will inspect the check valve next; I didn't know what that was. As for the pump itself, I'm pretty confident it has power to it -- when the timer clicks to "on," or when I manually turn it on, the pump will kick in and it's very audible -- plus the pump housing becomes warm. Also, the pump's installation instructions had suggested that I manually spin the shaft to ensure it's not stuck, so I had done that during installation. Okay, let me check that valve and I'll report back. THANK YOU.
 

AidanDanner

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The mystery deepens!

I inspected the check-valve, as suggested. It looks unobstructed. BUT: one of you had helpfully suggested emptying the tank before looking at the valve. That's something I've been wanting to do anyway -- flush out any accumulated sentiment.

So I watched a how-to YouTube video and proceeded. And I ran into an interesting problem that just maybe is related to this re-circulation issue?

After an initial cup or two of water, I couldn't get the tank to drain any further through the drain valve -- or, more precisely, it was draining at the barest of trickles. I understand the notion of needing to equalize the pressure, so I did everything suggested in the video: I opened up the tank's pressure-relief valve. I opened up various hot-water faucets around the house. Yet the stupid thing just would not drain!

Therefore I was able to open up and inspect the check valve, without first draining the tank.

Could this behavior suggest a problem with the water heater, and that's what's causing the re-circulation issue? (Note that the hot water around the house seems to have adequate pressure, and also that it gets plenty hot after letting it run for a minute.)

One final thing: out of curiosity, while the drain valve was open, I turned back on the cold water supply valve -- and water started to flow out of the drain valve at high speed...
 

Jeff Handy

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The drain valve often plugs up with sediment while draining.

Usually, you can clear it by opening and closing it several times, and repeat as needed if the flow slows down again.
 

Jeff Handy

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The check valve might be full of sediment also, but maybe not if you say it looks clear inside.

But if you took it apart with the tank still full, shouldn’t water have gushed out of it?

Pros on here can advise.
 

Geofd

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The mystery deepens!

I inspected the check-valve, as suggested. It looks unobstructed. BUT: one of you had helpfully suggested emptying the tank before looking at the valve. That's something I've been wanting to do anyway -- flush out any accumulated sentiment.

So I watched a how-to YouTube video and proceeded. And I ran into an interesting problem that just maybe is related to this re-circulation issue?

After an initial cup or two of water, I couldn't get the tank to drain any further through the drain valve -- or, more precisely, it was draining at the barest of trickles. I understand the notion of needing to equalize the pressure, so I did everything suggested in the video: I opened up the tank's pressure-relief valve. I opened up various hot-water faucets around the house. Yet the stupid thing just would not drain!

Therefore I was able to open up and inspect the check valve, without first draining the tank.

Could this behavior suggest a problem with the water heater, and that's what's causing the re-circulation issue? (Note that the hot water around the house seems to have adequate pressure, and also that it gets plenty hot after letting it run for a minute.)

One final thing: out of curiosity, while the drain valve was open, I turned back on the cold water supply valve -- and water started to flow out of the drain valve at high speed...
Maybe it’s been asked already, after the pump was changed we’re the screw driver stops opened all the way????????
 

Jeff Handy

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It looks like, if you open up the drain valve, you should get drainage from both the water heater AND from all the house plumbing hot water lines because that loop also drains right there.
Especially if you opened up the faucets on the hot setting.

So, either the check valve might be blocked, or the pump is not passing water.

Or else the drain valve is choked with sediment.
 

Jeff Handy

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It is pbly time to call in a pro, to solve your recirc line issue and to properly drain and flush the tank.

You should watch what the plumber does to flush the tank, for next time by yourself.
 

Geofd

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I'm totally stumped here, hoping someone can help. When we moved into our 1954-construction home about ten years ago, we had a copper re-pipe done, and also a hot-water re-circulation system installed. It's been working great, until about six months ago, when I began to notice that the water coming out of our master bathroom sink (which is the sink located farthest from our conventional storage-tank water heater) was taking a long time to get hot. Well, I figured it's gotta be the pump, right? So I bought a new one, nearly identical to the old (a Grundfos UP15-29SU) and successfully installed it. I was very proud of myself, because I know NOTHING about plumping.

Well imagine my surprise when that DID NOTHING. The water STILL takes a really long time to get hot. The old Grundfos pump was probably just fine. Something else is going on. But what in the world could it be???

Below is a pic of the heart of the system. Pump is brand-new, pump timer is old (repurposed off the original pump), water heater's from 2009:

View attachment 24670
 

Geofd

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Have you tested the outlet your plugged into for power, or use an extension
Cord and plug into another know good outlet
 

TomFOhio

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Look under your farthest sink and see if there is a device that hooks up to your supply lines. If you have this it
could be bad. The black fitting in front of the pump is what I am talking aboutgrudfos.png
 
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hukre

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Judging from the picture I assume that you have a dedicated return line from your master bathroom.
So you have a loop supplying hot water to yor master bathroom and returning it to the water heater through the pump and the check valve. I also assume that the return line is not connected to your other sinks in the house and that it only serves the master bathroom, correct?
We also can assume that there is no major flow restriction in the supply line to the master bathroom, otherwise you would not get a normal water flow out of the hot water faucet(s) in the master bathroom (although it stays cold for quite a while before it finally turns to hot).
I also assume that you don't have one of those black sensor valves under the sink, which are used for systems which don't have a dedicated return line.
All of this leads me to believe that the water is not moving the way it should in the return line.
Please check the following:
In the morning before you use the hot water in your master bathroom and with the recirculation pump already running for a while, turn on the hot water faucet in the master bathroom for a couple of seconds and verify that the water is cold. Then go to the water heater and check if the return pipe at the left of the pump (pump inlet) is hot or cold.
If it stays cold for more than about 5 minutes, you have a major flow restriction in the return line (or the pump is not pumping). Check if there is a shutoff valve on the return line under the sink, or wherever the return line tees into the hot water supply line; if so, make sure that valve is fully open. There should be no other device in the return line between the master bathroom and the pump.
If it starts to warm up after a few minutes, you have flow restriction, but not that severe. Here too, check if there is a shutoff valve in the return line that may be the culprit and needs to be replaced or fixed.
 
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