Taps not getting hot water

[tokyotecubate]

Hi all,

 

A bit of background - we are currently renovating our house and had new pipework installed alongside a heat pump as our main source of heating. The plumbing for the whole house was set up by a previous company who unfortunately aren't around anymore. 

 

The heat pump is just installed ( not fully commissioned) - however, on testing the hot water throughout the multiple taps in the house, we realized that some taps are not getting hot water. ( this is the first time we are testing the new plumbing in the house)

 

What could bee the cause? Is this caused by the individual tap fitting? Our fittings are mixer cartridge and are concealed valves, which would be a nightmare if we do need to check the cartridge.

 

The heat pump installer said that it could be either the mixer taps, or it could be concealed valves on the hot downservice pipework ( though honestly I am not too sure whether I fully trust this as we had had multiple instances where they weren't being fully transparent with the problems of the install).

 

Are there any ways to check the fitting and the cartridge without needing to cut the tiles ( as honestly it would be a nightmare to do so just to check if a cartridge is working properly) Just the thought off how to troubleshoot this is giving me nightmares.

 

Any input is welcomed - Thank you!

Edited April 10 by Nickfromwales
Typo fixed :)

[ProDave]

Dumb question.  Is there no water coming out of the hot tap?  Or is the "hot" water coming out cold?

 

Not such a dumb question when I as an electrician drove 40 miles for "no hot water" expecting an immersion heater fault, only to find no water coming out of the taps and they needed a plumber.

[ToughButterCup]

12 hours ago, tokyotecubate said:

...

Are there any ways to check the fitting and the cartilege without needing to cut the tiles ( as honestly it would be a nightmare to do so just to check if a cartiledge is working properly)

...

 

Mate, you need a surgeon .....😔

[Nickfromwales]

Worst case is the 1st fix plumbing has the hot and cold reversed, as these are very important to get the right way around (hot to hot and cold to cold etc). Does the wash basin tap work or are these concealed mixers too? Does water come out when hot is selected or zero water when hot is selected (test this fully away from the cold setting on the lever /tap).

[JohnMo]

Couple things spring to mind, assuming hot and cold are connected correctly.

 

If you have moved from an oil or gas boiler, the mixers maybe set up for high temperature hot water, so they are mixing in lots of cold. A lot of shower mixers have an adjustable mixer setting, inside the handle.

 

You are trying to store water at a temperature not suitable for mixers. You need water above 45 for many to work acceptably. (ours were not much use until over 47)

[tokyotecubate]

15 hours ago, ToughButterCup said:

 

Mate, you need a surgeon .....😔

thanks for fixing my typos - rage typing ( fuming with our heat pump installer due to extensive delays and multiple unresolved issues! ) surely doesn't help 😬

[tokyotecubate]

On 08/04/2025 at 21:22, ProDave said:

Dumb question.  Is there no water coming out of the hot tap?  Or is the "hot" water coming out cold?

 

Not such a dumb question when I as an electrician drove 40 miles for "no hot water" expecting an immersion heater fault, only to find no water coming out of the taps and they needed a plumber.

Yes there is water coming out, just that the water isn't heating up ..... I am going to the build this weekend to extensively test this again 🤞

[Nickfromwales]

On 08/04/2025 at 20:31, tokyotecubate said:

we realized that some taps are not getting hot water

Ok, so which ones work? 
 

Can you take your better half with you so one person can hold the hot pipe at the cylinder whilst the other person goes to open one of the non-functioning taps in the fully hot position. 
 

The new hot cylinder will have a ‘control group’ which looks like this, 

 

and you need to make sure that none of it gets even warm when running those outlets. 
 

The pipe at the top of the hot water cylinder will naturally be hot to the touch as it rises from the cylinder, so follow that pipe until it is cool / cold and that where you want to hold it to see if hot water travels out of the cylinder at all. 
 

Do NOT open the taps that work before this test or you’ll then heat up the pipe you’re testing with!

 

Report back if opening any non-functioning taps pulls any hot water out of the cylinder or if that control group gets warm.

 

This one may be tricky to solve so best to start getting through a process of elimination that doesn’t require paying for a plumber to come out.