Possible crossover issues in condo units

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Hi:

I live in a 9 floor condo building. I’m on the 8th floor. No hot water tanks in units; hot water is pumped into units just as cold water is.

A week ago, our building had the central hot water tanks inspected. This involved draining the tanks. After that, two or more riser tiers did not have proper hot water; my tier was one of them. I’d run hot water and it would take a few minutes to get warm and it wouldn’t get hot.

At some point, the corporation had a contractor come into my unit and he told me he had just changed some cartridges in other units in my tier; right after that, the hot water seemed better, but, hours later, the hot water problem resurfaced.

The next day, the contractor went from unit to unit, in my tier, checking to see if the shower valves had crossover. The valves are pressure valves; I think they have built in check stops; my valve is made by Aquabrass (photo included here). He didn’t test any other fixtures. His method of testing was to remove the faceplate, run the hot, turn it off, and then see how long it took for the hot side of the valve to cool down. Because it didn’t take too long to cool, he concluded that the valve was experiencing crossover. He said 6 other units also had this issue.

I did my own test. I turned off the cold intake to my unit, turned off my kitchen faucet valves, shut my washing machine valves (dishwasher is only a single supply hose), then went to bathroom sink, shut off the hot valve, and turned on the faucet all the way to cold (single lever faucet), and some water came out: anywhere from a drip to a very small flow, and it didn’t stop. I then turned off the hot water supply to the entire unit and the flow stopped. So, it would appear that there is some crossover going on at the shower valve. But, I don’t know for sure. There could be another source. I attempted to test the other faucets in my unit, but, the test was less exact because I can’t shut off shower/diverter water supply. Our units have heat pumps that deliver heat and cooling and I don't know for sure if they are connected to the water sources.

At some point, on the day of the contractor's second visit, the hot water issue resolved itself. And I was told that no other cartridges had been changed; he had to order them.

But, I now have perfectly hot water, with no plumbing issues at all. It's been good for about 48 hours now. This makes me wonder if I really have a crossover issue.

I had sent in a support ticket to Aquabrass. And they kindly told me they were sending me, free of cost, a new cartridge and new check stops. And in their email to me, they said (this is directly from their email): “this is very unusual for a pressure balance system to have a cross-over issue as it would have to severely damage the cartridge to allow water to by-pass. I'm going to send you the check stops as a no charge as there maybe more involved in the cross over issue.”

Also, the fact that a number of people had this hot water issue after inspection of the hot water tanks is concerning. I was told that this can happen because draining the tanks causes negative pressure, which can damage cartridges if they are already partially failing. According to my condo manager, there is only one company around that can do large hot water tank inspection; they have to drain the tank and walk through it. And my condo manager basically told me that unit owners just have to accept the fact that tank inspection can cause partially failing cartridges to fail.

It doesn't make sense to me that unit owners are responsible for cartridge replacement, when a bad cartridge can affect the water of the entire tier.

My questions:
-Should I replace the cartridge and check stops when I get them. I assume I can do this on my own.
-What do you think about what I was told about hot water tank inspection impacting cartridges?

The image is my shower valve.

Thanks in advance!
 

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I don't specifically know those Aquabrass cartridges at all.
I have had Kohler and KWC cartridges become bad and cause temperature drift/lack of hot situations and replacing cartridges in those cases solved the problem.
Your situation has so many possible source issues that it is very tough to assess.
Kudos to Aquabrass for sending you parts. We don't have their product around here. Never heard of them actually.
 
I don't specifically know those Aquabrass cartridges at all.
I have had Kohler and KWC cartridges become bad and cause temperature drift/lack of hot situations and replacing cartridges in those cases solved the problem.
Your situation has so many possible source issues that it is very tough to assess.
Kudos to Aquabrass for sending you parts. We don't have their product around here. Never heard of them actually.
Thanks for your reply.

Yeah, I was really happy to get that reply from them.

Are you able to tell me... are the big bolts on the valve (in the photo) where the check stops are located, and are they replaceable without replacing the full valve assembly?
 
yes, the 'big bolts' are the stops. they would only be check stops if they have a built in spring mechanism. if no springs then we call is just "integral stop".
The main brass body will be able to stay in place.
From what I see in your photo, the installation is quite poor due to no blocking or backing to stabilize and secure the valve. Outrageous and wrong. does it have much wiggle?
btw, i don't capitalize much due to a left pinky finger disability
 
Are the janitors closets with mop sinks and soap mixing stations on any floors, are there restaurants with commercial kitchens??????? After the hwh is there a master mixing station to temper the water before it gets to the units did the inspect the check valve on the return line,
 
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yes, the 'big bolts' are the stops. they would only be check stops if they have a built in spring mechanism. if no springs then we call is just "integral stop".
The main brass body will be able to stay in place.
From what I see in your photo, the installation is quite poor due to no blocking or backing to stabilize and secure the valve. Outrageous and wrong. does it have much wiggle?
btw, i don't capitalize much due to a left pinky finger disability
Really appreciate your time and help here.

I have decided to leave things as they are right now, because everything is working perfectly. I have taken the faceplate off a couple of times and didn't notice any wiggle. I was wondering why they didn't use the mounting holes in the valve.

Interesting fact: I didn't understand what you meant by, "capitalize". I've been using the free version of Google Gemini AI, and I decided to ask it for help in understanding what you meant, and it figured out that you meant capitalize words. And, no worries; I have no issues understanding what you wrote (other than the 'capitalize' thing, which is not a capitalization thing, lol).
 
Are the janitors closets with mop sinks and soap mixing stations on any floors, are there restaurants with commercial kitchens??????? After the hwh is there a master mixing station to temper the water before it gets to the units did the inspect the check valve on the return line,
Thanks for this.

I don't know if there are janitor closets. No commercial units here. Don't know about mixing station. What do you mean by return line?
 
Sounds like you have a main hot water shut off for your unit. Shut it off, then open the hot side of a faucet. Water should stop flowing after a minute or so, if it doesn't there is most likely crossover somewhere. Shower faucets are the most common culprit, but it cauld be any single handle faucet, or a two handle with both handles turned on and the spout blocked allowing the water to mix.
 
Sounds like you have a main hot water shut off for your unit. Shut it off, then open the hot side of a faucet. Water should stop flowing after a minute or so, if it doesn't there is most likely crossover somewhere. Shower faucets are the most common culprit, but it cauld be any single handle faucet, or a two handle with both handles turned on and the spout blocked allowing the water to mix.
Thanks. I did that test with cold (as per my original post) and also hot. And, yes, saw a drip to a very small flow.

But given that everything now works perfectly, and that I made no changes to my unit, and that it takes very little time to get really hot water to my shower tap, I am thinking that it’s possible that this very small flow I see when I test for crossover, might be my shower pressure valve working as it should. It might just be the way it compensates when there is full pressure on one side and no pressure on the other side. My valve has check stops; it also seems odd that I’d see exactly the same type of “crossover” when testing with hot and also with cold.
 
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