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Fluctuating and inconsistent temp at last fixture

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Hi Larry. I’ve toured your house!
i have a hot water recirculation system. I don’t know how the return line is plumbed because I’m too claustrophobic to go under the house. The bathroom in question was added at some point after the house was built. It has a sink and a shower.  Water temp becomes hot almost instantly at the sink although once in a while it’s noticeably less hot but still ok. The shower almost never delivers water hot enough to shower with at first but it warms up pretty soon. Usually the hottest water doesn’t arrive for a few minutes, if at all.  I’ve been mystified for years and assumed the return line may have been plumbed wrong near the shower. It’s about six feet from the sink and is presumably the furthest fixture. I haven’t addressed the problem since hot or “hot enough” water usually arrives “soon enough”. (Although it bothers me that even a few gallons usually go unused before the shower is tolerable. In summer I usually capture that water and use it to water the landscape but that’s a real hassle and not useful year round.) A couple of weeks ago i replaced the cartridge in the single handle (Pfister) valve, not because i had a good theory but because it was easy and cheap and i took a chance. It made zero difference at first. Then this happened: A few days ago “warm enough” water never arrived at all, let alone hot.  The water was warmer than the cold side, but not by much. Lukewarm. Whatever inconsistent fault there is in the plumbing was unprecedentedly severe that day, for whatever reason. In the latest test the water very gradually warmed up to hot, but not nearly as hot as the water at the sink, which is by far too hot to touch.  Ideas? Is there something I can try without going under the house? I could open up the wall behind the shower valve but of course I’d rather not. And I don’t think I’d understand the situation any better than I do now. Which is zero.  

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  • Jamie Hall
    Jamie Hall Member Posts: 23,635
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    Is there a location where you can positively close off the recirculation pipe? A valve on it? If there is, turn off the recirculation pump and close that valve and see if that makes any difference. The hot water will be slower to show up at the lavatory, but what I'm looking for is whether it's more or less the same time at the shower, and if it is any hotter.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    johnkern9068
  • mattmia2
    mattmia2 Member Posts: 9,942
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    That shower valve handle probably has a stop that controls how far toward hot it can turn. Did that get changed when you changed the cartridge?
    johnkern9068
  • EStark
    EStark Member Posts: 18
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    I was thinking similarly. Maybe a mixing value somewhere in the line used as a safety to provent scalding hot water, I'd find the cold water shut off then test for hot water if that works then you know what to look for ,value is probably in the wall not under the bathroom as the showers only 6ft from the sink, maybe in the sink cabinet or the water  value in the shower is bad or set wrong believe they have an adjustment 

    johnkern9068
  • johnkern9068
    johnkern9068 Member Posts: 12
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    Thank you guys. I can't figure out how to reply to each of you. Maybe I can't.
  • mattmia2
    mattmia2 Member Posts: 9,942
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    you can scroll up and press quote, reply to that comment, put the cursor where you want the second quote, scroll up and press quote for that comment.
  • johnkern9068
    johnkern9068 Member Posts: 12
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    Update:
    1. Thank you Jamie. Recirc pump off and ball valve in line closed. No change. Sink gets scalding hot water almost instantly. Shower turned gradually warmer but after 10 minutes was still not hot. Warm enough to shower, probably, but not hot. Not sooner. Not hotter. This is the condition I've been living with because you can almost always shower, even though something is clearly wrong.
    2. Thank you Matt. I don't see a stop for the valve handle. The new cartridge has the same amount of potential rotation as the last one. Full hot setting is at about 120-140 degrees (counterclockwise), same as before. Behavior is the same with the new cartridge. In any case, this might explain getting cooler water steadily but the water is gradually warming to a moderate temperature and staying there. Or, as sometimes happens, very hot water eventually arrives and I have to adjust handle too cool it to tolerable temp. Or, much more rarely, the lukewarm water never warms up much. Unless I need a cold shower (no comment) it is not okay. That happened recently, prompting me to get back on solving this. But it's very rare. The key fact here is the variability. Fluctuating hot water may be a poor description. It doesn't fluctuate at all during a shower. It's steady state or gradually getting hotter. Flow and temp don't change when toilet is flushed; temp might change a bit when another shower in the house is turned on. What fluctuates is how it behaves from shower to shower.
    3. Thank you EStark. Isn't the shower valve the mixing valve? If it has an anti-scald feature, isn't that also in the valve, either in the cartridge or somewhere else in the valve? I'm ready to open up the wall behind the valve but not convinced enough yet. Is it really possible that someone put a separate, presumably anti-scald device in the wall? The valve clearly has separate hot and cold supplies coming to it.
  • pedmec
    pedmec Member Posts: 998
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    You have to adjust the anti scald temperature on the valve. Read the directions. Most shower valve limit the temperature by limiting the rotation of the handle. Usually a gear type set up under the handle
  • johnkern9068
    johnkern9068 Member Posts: 12
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    Hang on. I took off escutcheon and saw a black plastic disc with stops. And apparently, temperature settings. However the stops don't limit the handle travel any more than the cartridge itself, which must also have stops internally.

    HERE'S THE QUESTION: CAN THIS CARTRIDGE BE INSTALLED UPSIDE DOWN? IS HOT SUPPOSED TO BE AT THE LIMIT OF HANDLE TRAVEL OR AT THE VERY BEGINNING?

    I took the cartridge out to inspect it and indeed found a disc that adjusts handle travel. However it was already at the maximum. When I put it all back together, I had somehow made it worse. Now all I got was completely cold water. Cold. Not warm at all. For some reason I tried other positions and lo and behold the water got warmer. A handle position very near the off position yielded extremely hot water!

    Did the plumber who put in the bathroom put the cartridge in upside down, all those years ago?! And when I replaced it, I got it wrong also? Or....is it now upside down but giving me the full range of water temps?!?!

    I will let the hot water pipes cool down. Then I'll turn on the shower valve and see if hot water shows up with the handle in the "wrong" position! WTH?

    Side note, the shower/tub valve in our other bathroom looks to be identical. Hot is at the far limit of the handle travel, just as I expected it would be.
  • mattmia2
    mattmia2 Member Posts: 9,942
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    Maybe the hot and cold supplies to the valve are reversed, although there are definitely some cartridges that can be put in in such a way that it reverses hot and cold.
    johnkern9068
  • hot_rod
    hot_rod Member Posts: 22,468
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    Do you have a tank type water heater? Does it have a thermostatic mix valve on it
    ?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    johnkern9068
  • johnkern9068
    johnkern9068 Member Posts: 12
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    The cartridge seems not to have a top and bottom but the idea that the supply lines were reversed makes sense. Sorta.  I’m glad I finally addressed it, you know, before another 13 years went by! Thanks everyone.  I think I’m good now.  

    (I don’t need to break open my wall and reverse the supply lines, do I? Please don’t reply unless the answer is no. 😏)
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,386
    edited December 2022
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    Hi, I just got in and seem to be a bit late to the party. Still, one thing that I didn't see mentioned is a simple cross connection test. This will let you know if there is any leakage between hot and cold. To do this, close the valve to the water heater and open any hot tap. If water stops running in seconds, there is no cross connection, which is good. That means it likely has something to do with the shower valve. @johnkern9068 , if you don't live too far away, I'd be glad to come have a look if needed.

    Yours, Larry
  • johnkern9068
    johnkern9068 Member Posts: 12
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    Hi Larry! I'm Melissa's husband. Tim and Becka are friends. We toured your off grid house when we were thinking of building. Anyway, I did the cross connection check you mentioned and it seems fine. I can't imagine how hot and cold could blend in my system, especially since it's only the one fixture that's affected, unless of course it has something to do with how the recirc system was plumbed at that furthest fixture. It would start lukewarm and gradually get warmer, but not in a way that was consisent shower to shower. I reached out for help when i had to have an (almost) cold shower the other day. What could be wrong with a (Pfister) shower valve that a new cartridge wouldn't fix? With the cartridge out it looks like a simple casting with two kidney shaped ports for water. Is there more going on back there than I'm aware of? All the regulation and mixing goes on in the cartridge, no? The fact that I now get fully hot water but it's at the beginning of the handle travel instead of at the end is mystifying. But if it works this way, I'm ready to move ahead into a beautiful future without understanding the plumbing. Nice to know: can a cartridge for this valve be installed upside down? (There's no obvious difference.) Is the problem explainable if the shower valve hot and cold connections were reversed at installation? If so, do I need to open up the wall and correct them? Why do I now have hot water but the hotter/colder direction of my handle is now reversed? So many questions!
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,386
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    Hi @johnkern9068 , It sounds like you can live happily with unanswered plumbing questions, but I would be glad to come by, and/or you could post photos of the shower valve here, and perhaps we can figure out if it’s installed backwards. I’m not familiar with that cartridge and if it can be put in wrong. Easy enough to find out 🤠

    Yours, Larry

    Ps, Just to be clear, I’d think of it as a social visit, no change to come have a look.
  • mattmia2
    mattmia2 Member Posts: 9,942
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    So let's think about this, if the cartridge has 2 ports on the back and it is the kind that you just rotate for temp and flow, it doesn't have separate adjustments for each, then one port has to be always the port at the near full clockwise rotation when flow just starts and the other port the full counterclockwise rotation. If you can put the cartridge in in 2 orientations 180 degrees out, then by rotating the cartridge 180 degrees you can swap hot and cold.

    Another option here is to find the manual for the valve and read it.
  • johnkern9068
    johnkern9068 Member Posts: 12
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    Thanks Larry and Matt. I'll keep investigating. I think I can identify the valve. I can certainly identify the cartridge. It's very common. And it has nothing in the installation (replacement) instructions related to a correct orientation in the valve. Meanwhile I've had a very nice hot shower. First time in a long time.
  • johnkern9068
    johnkern9068 Member Posts: 12
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    hot_rod said:

    Do you have a tank type water heater? Does it have a thermostatic mix valve on it
    ?

    Yes, tank heater. No thermostatic valve. All fixtures work well except the one. It's probably the furthest fixture but I'm not sure how the return line was plumbed. An error there was one of my theories but I'm not interested in slithering under the house to look, at least until all other options were exhausted. Due to fiddling around looking at the cartridge and the valve body and (accidently?) reinstalling the cartridge upside down, I now have hot water but it's maximum hot at the beginning of the handle travel, not at the top as it used to be. An identical or very similar shower/tub valve in another bathroom works fine and the hottest water is at the top of the handle travel. ?!
  • johnkern9068
    johnkern9068 Member Posts: 12
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    mattmia2 said:

    So let's think about this, if the cartridge has 2 ports on the back and it is the kind that you just rotate for temp and flow, it doesn't have separate adjustments for each, then one port has to be always the port at the near full clockwise rotation when flow just starts and the other port the full counterclockwise rotation. If you can put the cartridge in in 2 orientations 180 degrees out, then by rotating the cartridge 180 degrees you can swap hot and cold.

    Another option here is to find the manual for the valve and read it.

    The ports in the valve body line up with ports in the back of the cartridge and stay that way. Any mixing adjustment must happen inside the cartridge. Flow is restricted by law in California (pressure compensating gizmo in the shower head), so there's no change in flow after the first couple of degrees of handle movement from off.
  • johnkern9068
    johnkern9068 Member Posts: 12
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    I suppose it's possible that the wrong cartridge was installed at some point. It fits physically and works without leaking. And, for some reason it works "upside down". The cartridge I put in is exactly like the one that came out (as far as I can tell) except that the stem is plastic on the new one.
  • hot_rod
    hot_rod Member Posts: 22,468
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    If you nick the gasket or o rings  on some of those single  handle cartridges they can cross over. The Kohler plastic cartridges could be damaged easily or the o ring could sneak partially out when sloped in

    Some stem lube helps thing slide in easily 
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    johnkern9068
  • mattmia2
    mattmia2 Member Posts: 9,942
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    mattmia2 said:

    So let's think about this, if the cartridge has 2 ports on the back and it is the kind that you just rotate for temp and flow, it doesn't have separate adjustments for each, then one port has to be always the port at the near full clockwise rotation when flow just starts and the other port the full counterclockwise rotation. If you can put the cartridge in in 2 orientations 180 degrees out, then by rotating the cartridge 180 degrees you can swap hot and cold.

    Another option here is to find the manual for the valve and read it.

    The ports in the valve body line up with ports in the back of the cartridge and stay that way. Any mixing adjustment must happen inside the cartridge. Flow is restricted by law in California (pressure compensating gizmo in the shower head), so there's no change in flow after the first couple of degrees of handle movement from off.
    but if you turn the cartridge 180 degrees the port that was in the left is now on the right and vice versa.

    but it still opens one port first then blends to the other port. which of those is connected to hot and cold would be dependent on how it is assembled if you can turn it 180 degrees.

    the instructions mention an option for assembly if it is used in back to back installations but doesn't actually have that information in the online manual.
    johnkern9068