Hot Water Recirculation

[evox45]

Hello all, This is my first post so go easy on me. I recently installed a hot water recirculation pump in my home. it is the "Watts instant hot water recirculating system" https://www.homedepot.ca/product/watts-instant-hot-water-recirculating-system/1000728120. I did not install the included temp sensing valve as I have a dedicated loop. Now the problem im facing is when the pump is running it works amazing, hot water almost instantly. The problem is after the lines seem to fill with hot water and the pump kicks off (I have it on a 3 minute timer after I start it from a smart plug) my water becomes lukewarm. I notice this especially in my shower upstairs but at times even at my kitchen sink. Even if the water is on full hot it just stays lukewarm. The thing I don't understand most is that this doesn't happen all the time. Just sometimes, ill shower in the evening and have no issues than my wife showers say 15 mins after me and complains the water isn't hot at all. This never happened before I installed the system. I have tried to increase the heat of my water heater as well. I have included a crappy paint drawing of my setup. Hopefully that helps. I appreciate it in advance. Just cant figure out what's going on.

 

[Twowaxhack]

If it works great while the pump is on but you get unstable temps when the pump is off then your check valve is bad.

 

[MicEd69]

You have your pump in the hot water line from your water heater to all your fixtures. So, when the pump is off, water has to flow through a stopped pump to get to any fixture. The pump should be on your return loop either side of your check valve so that when the pump is off, the hot water has only to flow through the hot water lines to your fixtures.

And your check valve could be sticking at times as well.

 

[evox45]

You have your pump in the hot water line from your water heater to all your fixtures. So, when the pump is off, water has to flow through a stopped pump to get to any fixture. The pump should be on your return loop either side of your check valve so that when the pump is off, the hot water has only to flow through the hot water lines to your fixtures.

And your check valve could be sticking at times as well.

That really does make sense. I was not aware that the pump restricted flow that much. I will install it on either side of the check valve and give that a go. Thanks for the replies. Really appreciate it.

 

[evox45]

If it works great while the pump is on but you get unstable temps when the pump is off then your check valve is bad.

I can change the check valve but it was brand new a week ago. I guess you cant assume everything always works brand new.

 

[Twowaxhack]

I can change the check valve but it was brand new a week ago. I guess you cant assume everything always works brand new.

Make sure the check valve arrow direction of flow is pointed toward the water heater.

The pump is designed to be installed on the hot outlet of the water heater.

It’s also made to use with the bypass valve. I’ve never used that particular pump without a bypass valve.

Does it work perfect while the pump is running ? If so, it’s the check valve.

Circulator pumps don’t need a check valve if they’re running 24/7, but when the pump is off the flow can reverse if the check valve is bad. Also check that the pump is installed with the flow arrow pointing away from the heater.

 

[evox45]

Make sure the check valve arrow direction of flow is pointed toward the water heater.

The pump is designed to be installed on the hot outlet of the water heater.

It’s also made to use with the bypass valve. I’ve never used that particular pump without a bypass valve.

Does it work perfect while the pump is running ? If so, it’s the check valve.

Circulator pumps don’t need a check valve if they’re running 24/7, but when the pump is off the flow can reverse if the check valve is bad. Also check that the pump is installed with the flow arrow pointing away from the heater.

I checked the arrow direction on both and both are fine. It does work perfect while the pump is running but the water does get cooler after it stops. I tested it last night in the shower. The reason I went with this pump is it seemed simple to install for the average user. I’m not opposed to the idea of a different pump if anyone has a better suggestion. I should be able to buy some connectors to make it work so it’s on the return side and I bought an extra check valve that I can change as well. It’s definitely within the return window if there is a better option though.

 

[Twowaxhack]

The first thing I would do is run the shower with the pump OFF and see if the return line goes cold. That would prove cold water is flowing backwards.

I use a clamp on digital thermometer clamped on the pipe to see this.

Check valve may be defective.

 

[evox45]

The first thing I would do is run the shower with the pump OFF and see if the return line goes cold. That would prove cold water is flowing backwards.

I use a clamp on digital thermometer clamped on the pipe to see this.

Check valve may be defective.

Maybe I’m not understanding but how would the pipe ever get cold. The return line is plummed into the bottom of the water heater so it never makes contact with the fold lines. At the same time I'm not a plumber so I'm probably missing something.

 

[Twowaxhack]

Maybe I’m not understanding but how would the pipe ever get cold. The return line is plummed into the bottom of the water heater so it never makes contact with the fold lines. At the same time I'm not a plumber so I'm probably missing something.

As you use hot water from the top of the tank the water heater is being filled by cold water that’s conveyed to the bottom of the tank via the water heaters cold dip tube.

So the cold water is introduced to the water heater at the bottom via the dip tube and you return line is also connected to the bottom of the tank. With a bad check valve water will flow backwards through the return and be cold water after a minute or so.

 

[Twowaxhack]

If you have a swing check valve installed vertically that’s your problem. Install it in the horizontal position or get a spring check valve.

 

[evox45]

As you use hot water from the top of the tank the water heater is being filled by cold water that’s conveyed to the bottom of the tank via the water heaters cold dip tube.

So the cold water is introduced to the water heater at the bottom via the dip tube and you return line is also connected to the bottom of the tank. With a bad check valve water will flow backwards through the return and be cold water after a minute or so.

Learning something new! I didn't know that. Ok so I'll check the check valve tonight make sure it's not clogged. I checked with the manufacturer and it is a spring type so should be ok. I'm at work so will report back tonight. Thanks a lot for taking the time to respond to me.

 

[MicEd69]

The pump is designed to be installed on the hot outlet of the water heater.

It’s also made to use with the bypass valve. I’ve never used that particular pump without a bypass valve.

Yes, you are correct. And this system works great while the pump is running.

But with a dedicated recirculating line, the pump should be installed taking suction form the return line and pumping water back into the water heater drain line connection. You do, however, need to install the pump such that it meets the manufacturer's requirements as to orientation of the motor's shaft and location in the pipe.

 

[evox45]

Yes, you are correct. And this system works great while the pump is running.

But with a dedicated recirculating line, the pump should be installed taking suction form the return line and pumping water back into the water heater drain line connection. You do, however, need to install the pump such that it meets the manufacturer's requirements as to orientation of the motor's shaft and location in the pipe.

According to the instructions it has to be in a vertical position. I can probably move it to the other side but will have to get a few parts to do so. Is there a better unit for this task? Im using the expansion style of pex.

 

[MicEd69]

I've not used one of these, but it looks really interesting, especially in the Auto Control mode. They come in 1/2" sweat, 1/2" FNPT, and 1 1/4" Union connections. If you go with this, I would use the 1 1/4" Union connection with the appropriate adapters to you pex.

 

[Twowaxhack]

Yes, you are correct. And this system works great while the pump is running.

But with a dedicated recirculating line, the pump should be installed taking suction form the return line and pumping water back into the water heater drain line connection. You do, however, need to install the pump such that it meets the manufacturer's requirements as to orientation of the motor's shaft and location in the pipe.

I know I’m correct. I’m also correct that you can install the pump on the hot outlet and still have a return.

This pump is no different.

https://fasterhotwater.com/Dedicated Recirc System Installation.shtml

Location is optional.

 

[Twowaxhack]

The OP’s pump can be ran continuously or intermittently. When ran intermittently with a return it must have a properly placed check valve. When ran continuously with a return it doesn’t require a check valve.

The pump circulates the water. It’ll circulate the water no matter where it’s placed. When it’s off it can’t circulate the water and if you have a return pipe to the bottom of the water heater the flow can reverse and not go out of the top of the water heater, it flows to the path of least resistance that path can be the return line of it’s not checked properly.

 

[Twowaxhack]

According to the instructions it has to be in a vertical position. I can probably move it to the other side but will have to get a few parts to do so. Is there a better unit for this task? Im using the expansion style of pex.

If you install the shaft horizontal the heat will shorten the life of the pump.

So you install the unit vertically to avoid that.


I’ve installed several of the type pumps you have and there’s no problem with them. It’s basically just a pump because you’re not using the bypass valve

The bypass is a type of check valve……it’s opens and shuts on temp and allows water to flow one way.

Is this the pump you have ?


This Watts pump is made by Grundfos

It was originally paired with a bypass valve. I took it and used it on a solar hot water project that circulated hot water from a solar collector to a water heater that I used for an outdoor shower.

 

[Twowaxhack]

If you really want a nice circulator that has 3 speed selections stainless steel body then I suggest this Armstrong. It comes with its own check valve, you can see it in the middle pic.

 

[evox45]

If you really want a nice circulator that has 3 speed selections stainless steel body then I suggest this Armstrong. It comes with its own check valve, you can see it in the middle pic.
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Yeah that like looks like a nice one. So you were right. Got home took out check valve. Luckily it was just a push connect one. Sure enough I was able to blow air both ways. Than a small piece of what I'm assuming is a small piece of my water heater fell out. Now air only passes one way. Thanks so much everyone for the help, top notch! Hopefully showers better tonight.