Indirect water heater won’t stay hot

bellahtg

Hi all, 
After a couple of pinhole leaks, pipes were replaced. Now hot water temp is inconsistent on all faucets. Especially upstairs showers. Purged air with no benefit. Water starts hot, burner kicks on. Then after a few min gets lukewarm then cold and doesn’t recover. Occasionally, a full shower remains hot. 

We have no instructions or schematic on our system. Waiting on plumber but wondering if there is a simple fix. Worked perfectly before leak. Not sure if we are purging system correctly. House was built in 2007

Any suggestions are welcome
thanks
TB

mattmia2

Have you lived through winters with this system before?

Is the cap closed on that automatic air vent that is clearly leaking?

pecmsg

Hire a professional and replace all those Shark Bite  fittings

Larry Weingarten

Hi, I’d start with a few simple checks. Feel the temperature around the mixing valve when water is running. When a tap is running cool, is the temp out of the mixer still hot? Is there a recirculating line? If so, is cool water running backwards, from the bottom of the tank? Is there a crossover in the plumbing? Check by shutting off the cold supply to the tank and open a hot tap. Does it stop running pretty quickly?

Yours, Larry

bellahtg

This is our 2nd winter. Never had an issue w/ hot water before the leak. The cap is closed and that has never leaked since we have lived here. All the pipes are hot that should be and the water in the tank is hot. 

No plumber coming out until late next week.
Larry- we didn’t chg anything just shut everything off to replace pipes that were leaking. So, shouldn’t be a crossover. A plumber did the work but not sure how knowledgeable he is about the system 

Thanks for the comments. 

The first winter we did have some hvac issues, after turning up the water temp to 140 and adding upstairs valves, that was fixed. Few people know how to work on this system in our area. We had 5 different hvac guys come out to find someone that was familiar w the set up.
Now we need a plumber that knows what to do w it. 

bellahtg

Not sure about recirculating line. May be too complicated for the level of our know how.

mattmia2

The automatic air vent won't vent air if the cap is tight(although it looks like it will leak when you open it). Could see if air comes out when you open it.

mattmia2

Am i missing something or does the boiler water circulate through the indirect before it gets to the heating zones?

bellahtg

I think it circulates through the indirect (coil) then out to the zones. 

Will try the cap. Never touched it before. Nothing is labeled except the hvac line. We really have no idea. Had to learn how to prime lift pump when previous owner left us w an empty tank. We are learning as we go. Obviously.
thanks again for the suggestions 

Zman

What you have there is an absolute mess. Rube Goldberg would be envious , You appear to have an instantaneous hot water boiler that for some reason is piped to all the taps on an indirect hot water tank. There also seems to be a heating component randomly tied into all of this.

I think someone is using the word "Plumber" a bit loosely, you may want to check some credentials. I have never met a licensed plumber that would use shark bites and pex on a job like this.

Your best tool for troubleshooting this is going to be your hands. When you run the hot water, the pipe going straight into the wall off the mixing valve should feel hot as should the inlet to the recirc pump.

mattmia2

Oh, that boiler I can't identify is actually a tankless water heater? If that is the case, your first priority here is to not get legionnaires disease.

bellahtg

@zman
yes it is a mess. The “plumber” that originally did the work was during the house build. The plumber that did the shark bite was just doing a quick fix for the leaks, until we can get someone else out. 

The inlet valve and recirc pipes  hot. 

Hubs agrees,Rube would be proud. You should see our pump house, it’s just as impressive.
thanks for your input

bellahtg

@mattmia2
My understanding is it’s a closed coil system. Water is to heat coil. It’s not passing over any potential bacteria. It heats to 140degrees currently. 

Def something to consider though, I do appreciate the comment. 

mattmia2

It looks to me like the coil in the indirect, the tank connections of the indirect and some domestic heating piping are all tied together.

bellahtg

The upstairs separate bath has continuous hot water. All other showers and faucets are intermittent. Sometimes start off hot then go cold. Sometimes take forever to get hot and stay hot sometimes not. The system is making hot water. 

Heater (hvac) works fine. 

Doesn’t matter what time of day or usage- no rhyme or reason to it. Will try drawing out 5 gallons and bleed any air out. 

Then refill
maybe water isn’t continuously reaching coil 
🤷🏽‍♀️

Larry Weingarten

Hi, If I were the plumber coming to your house to troubleshoot this, I'd listen to you about the history of the system, and then I'd test everything, because good troubleshooting doesn't allow me to make assumptions.

What you just described sounds like a crossover in the plumbing. What brand of shower valve and single lever faucets do you have? Some are known for this problem. Are there any shutoff valves on shower arms?

Sometimes you can only learn what's wrong by discovering everything that's right. The one left standing becomes the culprit

Yours, Larry

mattmia2

Are all those pipes disappearing in to the wall domestic hot water or is there space heating from this system as well?

rick in Alaska

So from what I can figure out, there is an air handler hooked to this setup. The two lower pipes are the supply hot, and the return. Then the top three pipes are hot, return, and cold supply for the domestic.
So, the boiler isn't technically what I would call a tankless heater. It has about a three gallon tank in it if I remember right.
From the looks of things, the "boiler" heats the water in the storage tank, then goes straight to the air handler, and also splits off to the domestic mixing valve.
This is a tough one.
First, when the water starts going lukewarm, is the pipe on the top of the storage tank hot, or warm? If it is hot, is the pipe going out of the mixing valve, the top left pipe, hot?
You said the boiler starts right away on a draw for hot water. Does the boiler keep running when the water starts going warm, and if so, for how long?
Does your heat work ok?
The top center pipe, is it warm coming out of the wall?
Rick

neilc

so one domestic hot works correctly all the time,
and the other hots go cold?
I would suspect the one that keeps working, as the one that is the trouble for the others,
or is it piped on a significantly separate riser set?

bellahtg

@rick in alaska
thank you for responding, what you are saying is making sense. That is what we have going. 

When the water starts to cool or is cold the the pipe on top is lukewarm 
the others stay hot.
The boiler kicks on and stays on for 45 seconds.
i tested at kitchen sink had immediate hot water then went lukewarm after a few minutes

rick in Alaska

So when the water goes warm, does the top right pipe get warm where it goes in to the wall? How about the top center pipe. Is it usually warm, and then gets hotter or colder as the shower gets warm?
When yo say the to pipe gets warm but the others stay hot, do you mean the pipe coming out of the top of the storage tank gets warm? And does it stay the same temperature at the top of the tank as it does at the mixing valve?
You might try this experiment: Close the valve on the pipe going in to the wall on top center. Make sure to unplug the Taco recirculation pump. See if that makes any change. If that doesn't, then try turning your heating thermostat down, and then close the two valves on the bottom that go in to the wall and see if that changes anything.
Rick

bellahtg

@“rick in Alaska”
We tried all the experiments. All the pipes stay hot when shower or sink faucets turn cold. Pipes  are equally hot. 

Isolating experiments yielded same results…. Boiler kicks on for 45 sec then water runs cold. Pipes remained hot - except for the ones valves were closed 
meanwhile, the separate from shower bath tub remains hot consistently and does not turn cold.
That is the only consistent hot water source.

@neilc mentioned we should suspect that one. Idk how to tell if it has a significantly diff riser set??
they all seem to be coming from the same system. It’s a tub we rarely use. (Until now)

@Larry Weingarten mentioned the faucets-
we have one shower w a shut off and one without 
one is a waterpik the other is an Amazon off brand
faucets are price-Fischer but none of these gave  us any trouble. Problems started when we sprung a small leak and replaced the pipes w the sub standard 

Ones until we get someone out. 

We have not changed the configuration in any way. 

We had endless hot water previously . Water pressure was only an issue if we had showers laundry or dishwasher going all at the same time. 

We have hard water and are filtering lots of iron from our well- also not new. 

rick in Alaska

Do you know if you have one of those mixing valves for your toilets that add warm water to them? Those things are notorious for plugging up the little check valves inside, and causing cross connections.
Rick

bellahtg

@rick in alaska
Was just feeling around on the pipes with everything running as before too left into wall w mixing valve gets progressively cooler as it goes into wall
Right now , whereas it was equally as hot as the others before but now that water has run cold that pipe is cool

bellahtg

It’s very possible that the top right is what is the working tub “feed/riser”
???
That pipe stays hot hot

rick in Alaska

If you are saying the line leaving the mixing valve is cooling off, is it still hot on the pipe on top of the mixing valve, and is the line on the bottom cold?
Rick

bellahtg

@“rick in alaska”
the bottom pipe into mixing valve is hot
the top from indirect is hot at the horizontal but cool on the vertical
and the pipe from mixing valve to wall is cool
we have no hot water turned on right now- if that makes a diff?
no toilet heater but that sounds fancy

rick in Alaska

See what happens with that combination when you run hot water.
Some people use a mixing valve on their toilets to keep them from sweating. In my climate, I have never seen a toilet sweating that wasn't also leaking. Since they are so prone to failure, I just take them out.
Rick

mattmia2

Was one of those valves closed or partially closed before to force a certain path or some of them partially closed for balancing?

neilc

the tub that always runs hot,
is that the one with the separate valve to shut off water flow?
could you post a picture of the separate valve and the mixing valve, shown together,
or, try shutting the water flow off at the mixing valve, leaving the separate valve open,

rick in Alaska

neilc:
I believe the two pipes with valves on them that are below the three top pipes, are heating pipes going to an air handler, and not to the tub.
It sounds like if the pipes around the water heater stay hot when the water is being used, but the fixtures go cold, then there has to be some kind of cross connection in the house on the other side of the wall.
Rick

neilc

I'm with ya Rich,
that's why I'm asking about the fixture that works full time,
and if it's the one with the separate shut off or not

bellahtg

hey all, 
made some progress yesterday .  Plumber came by and replaced 
pipe above recirc valve to a 90 degree. 

Water is consistently staying hot on all faucets now. 

Maybe that is what a cross connection is? 

It was giving back pressure?

thanks to all for the great input. We learned a lot from you!!

bellahtg

Btw- these are all the pipes and valves that run all the faucets in the house
nothing is separate.
seems as though , there have been a lot of add ons t/o the years. 

The indirect was probably and after thought. 

The garage flooded (storm)at one time and that may have caused changes in the set up. 
Thanks again
glad we found this forum

rick in Alaska

That makes less than zero sense that changing that fitting would affect anything, but I guess if it works.....
Rick

bellahtg

oh dang , well, maybe it’s not over yet. It was a 90 before the leak 

I was thinking maybe back pressure was shutting off some sensor or something 
but I am really clueless 

rick in Alaska

As long as it is working, leave it alone! Strange things can happen in these systems that sometimes make no sense. Maybe by the system being shut down again that some piece of debris got dislodged somewhere and is now gone. Hopefully what ever happened, stays fixed.
Fingers crossed for you. This was a stumper.
Rick

mattmia2

Are any of the valves in a different position now?

bellahtg

@mattmia2
all valves are still open