Why is water not hot coming out of the faucet on the far side of the house?

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haeffnkr

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Hi,
I have a tankless water heater. I have a hot water recirc loop with a taco pump. I have a bosch 4 gallon electric water heater to keep the loop hot.
I have a T-K1 tankless water heater linked here https://www.takagi.com/media/48144/T-K1.pdf

In the winter I kick up the water to 131 output temp ... in the summer the basement and the ground water is hotter so I keep it at 121 output temp.

Last 2 days I the Moen mixer one handle shower faucet was on FULL hot but the water was just barely warm enough to take a shower comfortably. I have replaced the cartridge in the shower faucet a couple of years ago. Wife is hopping mad... She goes to the kids bathroom right above the tankless heater and has no issues in that shower with the same model faucet/shower.
I take a shower myself a few minutes later and have the same issue and keep the water in the shower running full on hot per the faucet then reach over the the vanity water is so hot you can not keep your hand under it. This bathroom is about 55 feet from the tankless heater on the other side of the house.

An hour later I test 2 handle tub next next to the always weird shower and it too is not not coming out of hot only faucet after running it for 2 minutes. Vanity is SMOKING hot. I leave on the water on in the tub, vanity then go to the garage sink on the other side of the wall and then that water gets very hot. I go BACK in the bathroom and now the shower and the tub are all HOT. My definition of HOT is what the water temp set to on the heater. 131 .. then 140 ... can't hold my hand under it at length



I am so confused.

Water pocket in the line? what?

I have seen this a couple of times over the past couple of years in my kitchen as well. I have 2 sinks in the kitchen. All of sudden or maybe the first time you turn on the water in the main sink... just warm water... wait for the cold to flush out ... still warm/cold ish.. Turn on the little bar sink in the kitchen and HOT ... go back over the main sink HOT.... turn off bar sink... use main sink as normal? WTF is going on?

Sorry to ramble... Ideas and thoughts appreciated as to how to fix this crazy house.

thanks haeffnkr
 
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Reach4

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Water pocket in the line?
That's not a thing.

So with hot still coming out of the lavatory, you still only get tepid water on the tub/shower, I think you are saying
 
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haeffnkr

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That's not a thing.

So with hot still coming out of the lavatory, you still only get tepid water on the tub/shower, I think you are saying

Yes, in summary.... yesterday and today I took a shower with faucet full on hot and it was warm/tepid. Now I just tested it again twice over the 2 hours and the shower and it HOT.

My tankless water heater is set to 131 output. When ever I have issues... I always test the water out of slop sink right next to the tankless water heater. The tankless heater is on and the water in the sink next to the water heater is HOT. I have measured it before with a known good thermometer it reads what the output should be. When I test it on the far end of the house I get some temp loss... a few degrees of temp loss due to cold copper... and a upper 60s basement, expected... but multiple times in 24 hours, intermittently. The water temp out of the shower and tub next to the shower WAS not quite hot enough for a shower... did not measure the temp. NOW the water it hot again.

Why would it be intermittent? Why would the water be hot in faucets close to the heater but not hot farther way? When I say not hot.. I am talking 25-30 degrees less in temp.

thanks for your help !!!!
haeffnkr
 

Terry

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Is there anything like a shutoff at the shower head? Sometimes people leave those closed when not in use and leave the shower handle on, which causes water to cross over in the valve.
 

haeffnkr

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Is there anything like a shutoff at the shower head? Sometimes people leave those closed when not in use and leave the shower handle on, which causes water to cross over in the valve.
No ... faucet goes up the wall to a shower head with no shut off on the head. Note I had the same issue on a 2 handle tub faucet next to the shower at the same time with the shower when I was testing things earlier. I believe that with 2 different faucets acting the same way at the same time that eliminates the faucets.
 

Reach4

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No ... faucet goes up the wall to a shower head with no shut off on the head. Note I had the same issue on a 2 handle tub faucet next to the shower at the same time with the shower when I was testing things earlier. I believe that with 2 different faucets acting the same way at the same time that eliminates the faucets.
But I think you say that the lavatory emits hot water at the same time that the shower emits cool/tepid water. If that is accurate, I think that eliminates the WH as the problem. If it is not the same time, but is sequential events, then try it at the same time. Simultaneous flows.
 

haeffnkr

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But I think you say that the lavatory emits hot water at the same time that the shower emits cool/tepid water. If that is accurate, I think that eliminates the WH as the problem. If it is not the same time, but is sequential events, then try it at the same time. Simultaneous flows.

Yes at the same time the lavatory was hot the the tub was tempid, this morning. Yes I have seen it yesterday that the shower was tempid and the lavatory was hot at the same time. This is all in the master bathroom. with the shower, tub and lavatory faucets are all within a 6x6 square.

Later this morning, I was testing, the 2 handle tub and the 1 handle lavtory both had tempid water at the same time, left them running. Then I turned on the sink in the garage on the other side of the master bathroom that is within a 9x9 square of all 4 faucets , then the garage sink got hot, turned it off. I got back to the master bath and the other faucets got hot... WTF.

I have since tested these faucets in the master bath 50 plus feet from the water heater a few times so far today and the are all getting hot again.

I have the water heater, on the other side of the house, set at 140 F output, raised it from 130 today.... I measured the temp in basement slop sink just 3 feet from the heater and it was 129 F, to hot to hold my hand under ... I measured the temp in the master bath at the tub, sink and shower and they are all about 127, as expected, working as expected... now.

It is like for some reason the faucets on the other side of the house, intermittently, are feeding back into the return loop and not going flowing to the faucet. I have check valves in the system. I have a taco pump running to always keep the return loop hot.

Every few years I have to replace the bosch water loop 4 gallon heater as it fills with crud and starts to leak. It is not leaking now... but I am out of options. I am also going to check the flow and the dielectric fittings to my tankless heater soon and see if they are full of black gunk and maybe the flow is getting pinched off and causing weird stuff.

Baffled.
 

Tuttles Revenge

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Definitely not the water heater that is the issue. It defintely sounds like a hot/cold crossover issue which is the most difficult plumbing issue to track down and diagnose.

On another note: Turning up the hot water to 130 in the winter just makes the water heater put out less hot water in the winter. It has to spend more energy to heat up colder water to a hotter temperature.
 

haeffnkr

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Definitely not the water heater that is the issue. It defintely sounds like a hot/cold crossover issue which is the most difficult plumbing issue to track down and diagnose.

On another note: Turning up the hot water to 130 in the winter just makes the water heater put out less hot water in the winter. It has to spend more energy to heat up colder water to a hotter temperature.

Tell me more about what a cross over issue is? How does the water go from the hot side to the cold side in the pipes?

thanks haeffnkr
 

Tuttles Revenge

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Crossover happens in situations where a valve that mixes hot and cold allows hot and cold to mix. Sometimes it happens when a pressure balance shower valve is installed with a shutoff on one of its outlets or from kitchen faucets that have touch or motion sensors to turn them on/off which are installed without their check valves in place. I've seen it in restaurants that have pre-rinse faucets that mix hot and cold with that big sprayer on the spring loaded hose. Even hot water recirculation can send water backwards into the cold or vice versa if its not set up properly.

Tracking it down can be very difficult because not every situation is the same
 

jadnashua

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On any single handle faucets, while your shower is tepid, shut the cold valve to each, one at a time. If your shower gets hot, the cartridge at that faucet is leaking internally, giving you a cross-over...mixing hot and cold. The water will take the path of least resistance.

A defective check valve in your recirculation system is a good thing to check...that happened to me a couple of years ago. I knew immediately what was wrong and fixed it.
 
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