This is the mixer for a water recirculaton system. It's what allows the water in the hot line to return in the cold line back to the water heater. This should be on an appliance somewhere near the furthest point of water travel. It might be tucked away under a sink somewhere.

https://www.plumbersstock.com/...19709&sc_intid=19709

Interesting. My recirculating setup has a dedicated line run from hot water point furthest from the water heater.

Getting hot water at other fixtures would seem to exclude any problems with his recirculating system. I would think any sort of mixing valve in the recirculating system would be inline after any outlet valves. Every hot water valve would have a direct path from the water heater.

Seems to me the issue is the valve at the shower. The ones I’ve seen are accessible from inside the shower by removing the handle and then removing a trim plate. You probably have to use a manufacturer’s specific tool to pull the valve out of the valve body. Delta and Moen will send free replacement valve cartridges.

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Originally posted by maladat:

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Originally posted by PASig:

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Originally posted by flesheatingvirus:


I actually don't recall a mixing valve during construction

There’s got to be one, they are required. It’s what keeps you from getting scalded if someone flushed a toilet or having your water go ice cold on you if someone starts the dishwasher while you are in the shower. It’s right behind the shower water control knob or lever usually.

I think he meant the valve on the recirculating system that allows the hot water return, not the thermostatic mixer in the shower.

You are correct. I'm talking about the recirculation system mixing valve.

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Originally posted by alteon180e:
interesting. it should be a mixer/control at that shower or along the way. i doubt its a leak or something.
have you looked at the service stop screws on the mixer? or is there any other mixer/shower along the way to that shower? they make smaller ones for faucets and such that ive seen with service stop/screws. plumbing use to make more sense...

i had my tankless act up years ago, and it ended up being a bad thermometer at the inlet. but that affected the whole house i believe.

That's something I hadn't considered yet. To get to the service stop screws on the shower mixing valve, I'd have to remove the face plate. I didn't need to do that to get the cartridge out, so I haven't. I may just do that. Perhaps the hot one isn't 100% open or it needs to be opened/closed to dislodge some buildup?

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Originally posted by jeffxjet:
This is the mixer for a water recirculaton system. It's what allows the water in the hot line to return in the cold line back to the water heater. This should be on an appliance somewhere near the furthest point of water travel. It might be tucked away under a sink somewhere.

https://www.plumbersstock.com/...19709&sc_intid=19709

That's what I was looking for. I checked under every sink and even in the construction photos of everything in the walls. I didn't see anything like that. I'll post some example shots shortly.

These are each of the master sinks:



Here is the master shower, VALVE NOT INSTALLED yet. The valve obviously goes where all the lines meet at ~waist height.



If I go to the kids bathroom at the other end of the house, we have a similar setup. This location is actually the furthest away from the water heater.

Their dual sinks:



Their toilet:



Notice how each of the water lines has a loop on it where it exits the slab. They are like that throughout the house. Is that some kind of different design that doesn't require a recirculation mixing valve?

I also have pics of all of the water lines before the slab was poured if we want to get real dirty.

The loops at each area where PEX exits the concrete is the feed to somewhere else. They typically don’t bury connections under or in concrete because concrete is acidic and will destroy the crimps leading to leaks.

That matches what I saw before the slab was poured. I didn't realize that's how they did that, but it makes sense. It wouldn't be fun to try to fix a connection under a slab.

Thanks!

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Originally posted by flesheatingvirus

That's what I was looking for. I checked under every sink and even in the construction photos of everything in the walls. I didn't see anything like that. I'll post some example shots shortly.

It shouldn’t be in the walls. It should be out in the open. The pump in your heater forces hot water into the lines and it has to return back to the cold inlet via the cold water lines. If you don’t have that valve you don’t have a reciculation system. It’s possible it got buried in the wall at your shower after the fixture was put in.

Do you have pictures during construction after the valve assembly was installed?

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Originally posted by jeffxjet:

It shouldn’t be in the walls. It should be out in the open. The pump in your heater forces hot water into the lines and it has to return back to the cold inlet via the cold water lines. If you don’t have that valve you don’t have a reciculation system. It’s possible it got buried in the wall at your shower after the fixture was put in.

Do you have pictures during construction after the valve assembly was installed?

is it possible that the recirc loop has a dedicated return line and not using the cold?
That is what I have, farthest sink has a T on the hot, one to the sink and then one home run back to a T on the inlet of water heater.

Yeah. Thats possible. I would assume most plumbers would try to cut costs and not have a dedicated line back to the water heater. That would be better i think.

Yep. My last house was plumbed at initial construction with a dedicated return line for the hot water recirculation pump.

You may have a check valve near the water heater that is hanging open, I've seen systems like that, in fact I installed one in my recirc system in my house, that way I needed no pump. Has worked great for 20+ years.

Of course, a photo of the shower valve right after install but before they put up the wall backing is one of the few I didn't get.

I'm really starting to lean on the possibility of dedicated return lines. I may be able to trace that using the pictures of the lines laid out before the slab was poured.

HOWEVER, I performed another experiment. I pulled the shower mixing cartridge (one of these and spec sheet), leaving an open port. I then just turned on the HOT side, mimicking the hot dial turned to max. I checked the temperature, it maintained 122F. That's pretty close to the 125F water heater setting, considering the distance. It seems like that narrows it down to the cartridge. Plus, it seems like that wax/piston design is a possible failure point. It was an informative video on that website, though.

UPDATE: I just heard back from the manufacturer; they'll send me a new mixing cartridge for free. Nice! Once it comes in (and hopefully fixes the issue), I'll update this thread.

This message has been edited. Last edited by: flesheatingvirus,

That fixed it!

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Originally posted by PASig:
There’s got to be one, they are required. It’s what keeps you from getting scalded if someone flushed a toilet or having your water go ice cold on you if someone starts the dishwasher while you are in the shower. It’s right behind the shower water control knob or lever usually.

They are required by current code. Previously, what kept one from being scalded was having the plumbing lines properly sized. Apparently, there were too many bozos running half inch lines for distribution and customers bitching about the problems that resulted so our gooberment decided to help us by mandating mixing valves. Sigh, competence is sure nice when one can find it.