Hot water issue

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164 posts

Master Geek
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#3279053 4-Sep-2024 19:20

Bung:

On the side of the valve that is visible both inlets are marked "O". Can you see if the other side has H & C? Are they in right place?

The valve appears to be a Reliance Heatguard.

H is from cylinder , so it was correct installed.

Bung

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#3279054 4-Sep-2024 19:29

Just to confirm, when you say from the cylinder you do mean the top of cylinder?

RunningMan

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#3279056 4-Sep-2024 19:38

As a quick test, grab each of those copper pipes to feel the temperature, both when working and when the issue appears. Some should be quite hot so be careful.

That should give some indication of where the issue lies.

I'm still a bit confused as to the actual symptoms though. When the issue occurs, is the temperature wrong, or is there no water flowing (i.e. tap is dry)?

1cloud

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Master Geek
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#3279058 4-Sep-2024 19:46

Bung: Just to confirm, when you say from the cylinder you do mean the top of cylinder?

correct, one is straight out from cylinder and the pipe is hot. The other one is just the relief valve.

1cloud

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Master Geek
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#3279059 4-Sep-2024 19:52

RunningMan:

As a quick test, grab each of those copper pipes to feel the temperature, bith when working and when the issue appears. Some should be quite hot so be careful.

That should give some indication of where the issue lies.

I'm still a bit confused as to the actual symptoms though. When the issue occurs, is the temperature wrong, or is there no water flowing (i.e. tap is dry)?

the one straight from cylinder is really hot and also from tempering valve (maybe I should check it again for tempering valve when it is not hot).

when it occurs , there is no water flowing at full hot (all the mixers) and no warm

tweake

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#3279061 4-Sep-2024 19:59

i wonder if a bit of rubbish has gotten into the cold water expansion valve (or its one way valve). if that blocks, it won't send water into the hot water cyl so hot water flow would stop. i've had issues before with plumbers fibre getting inside the pipes.

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Bung

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#3279068 4-Sep-2024 20:26

Well I'm tending to understand why the plumber is stumped. I've now found 2 sets of Reliance Heatguard specs showing opposing H&C connections. I'm giving up and reverting to sampling red wine.

SomeoneSomewhere

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#3279094 4-Sep-2024 23:03

tweake:

i wonder if a bit of rubbish has gotten into the cold water expansion valve (or its one way valve). if that blocks, it won't send water into the hot water cyl so hot water flow would stop. i've had issues before with plumbers fibre getting inside the pipes.

Cold water expansion valve is a relief-type valve that dumps water overboard. It shouldn't cause this issue.

However, a stuck check (non-return) valve or pressure reducing valve would absolutely cause this issue.

Again, when the issue is occurring, try exercising the temperature and pressure relief (TPR) valve. It should be at the top of the tank with a little lever, and dump hot water down a drain pipe. If it dumps hot water, then your problem is somewhere on the hot side of the cylinder. If it doesn't dump water, your problem is somewhere on the cold side of the cylinder.

1cloud

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Master Geek
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#3279127 5-Sep-2024 07:48

Bung:

Well I'm tending to understand why the plumber is stumped. I've now found 2 sets of Reliance Heatguard specs showing opposing H&C connections. I'm giving up and reverting to sampling red wine.

any chance the replaced tempering valve is also faulty? Thanks

Bung

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#3279133 5-Sep-2024 08:03

Sorry not a plumber. When I saw the install didn’t match the first documentation I found it seemed obvious. The trouble shooting mentioned crossed over connection. Then when you found H&C matched pipes I found another spec PDF with labelling matching yours. I wouldn't have thought the valve was able to have connection assignments swapped like that. Find the model number on the valve and look for its manual.

tweake

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#3279353 5-Sep-2024 17:45

SomeoneSomewhere:

tweake:

i wonder if a bit of rubbish has gotten into the cold water expansion valve (or its one way valve). if that blocks, it won't send water into the hot water cyl so hot water flow would stop. i've had issues before with plumbers fibre getting inside the pipes.

Cold water expansion valve is a relief-type valve that dumps water overboard. It shouldn't cause this issue.

However, a stuck check (non-return) valve or pressure reducing valve would absolutely cause this issue.

the cold water expansion valve, non-return valve and pressure reducing valve is all in one. its 3 valves in one "valve".

catch is you can repair them with a cartridge, but i suspect that it doesn't replace everything. which can trick you into thinking its not the problem.

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SomeoneSomewhere

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#3279357 5-Sep-2024 18:16

Ah, I didn't catch that there was all-in-ones. I don't think I've looked closely enough at anything modern with one.

The expansion valve itself shouldn't be an issue but the non-return and pressure reducing parts sticking shut would certainly do it.

Again, dump some hot water using the TPR valve while the system is not working. If hot water comes out, it's a tempering valve issue. If no/minimal water comes out, it's a cold water supply issue.

1cloud

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Master Geek
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#3279383 5-Sep-2024 20:34

SomeoneSomewhere:

Again, dump some hot water using the TPR valve while the system is not working. If hot water comes out, it's a tempering valve issue. If no/minimal water comes out, it's a cold water supply issue.

It is happening now, and I released the TPR and hot /warm water came out. You reckon the replaced tempering valve is faulty ?

SomeoneSomewhere

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#3279384 5-Sep-2024 20:37

Could be tempering valve or maybe something downstream of it, but that shows that pretty much all the cold water side is OK.

I don't fully understand the four-port combination cold water valve, so I'm not sure if it's possible for it to supply cold to the cylinder but not to the cold inlet on the tempering valve.

djtOtago

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#3279407 5-Sep-2024 23:24

If you got hot water from the TPR that shows, there is hot water and pressure in cylinder, so I would assume input to cylinder is OK.

From here I would just remove the Tempering valve and try for a few days without it in the system.

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