No hot water coming out when tap turned on in shower

[Dan0001!`]

Hi all, I have an issue with our shower's hot water. The shower is operated using two separate taps for cold and hot water. When the hot water tap is turned on, no water at all comes from the shower head - not even a drizzle. However, when the cold water is turned on it flows freely. The hot water tap itself appears to turn freely to both a closed and open position (the turning function doesn't appear seized). Hot water is available from other taps within the house. The hot water service is quite an old system and located in the ceiling.

I removed the tap shroud and took off the brass fitting, initially expecting this to be the spindle to inspect the jumper/valve. However, I then realized this was a brass extender as the remaining plumbing was inset further within the wall cavity behind tiles. After removing the extender, I can see the shaft of the jumper/valve, however cannot remove this as it is enclosed within the spindle. I used some long nose pliers and the jumper/valve can move freely within the spindle and doesn't appear jammed closed etc.

I did this after turning off the mains line and draining the hot water system (there doesn’t appear to be/can’t find an isolator tap from the hot water in the ceiling). A small amount of hot water came out of the outlet when the valve shaft was wriggled/moved around with a pair of pliers; I believe this is water remaining in the piping and indicates that there isn’t a blockage?

I'm not a plumber and have limited experience; I've changed a few jumper/valves on a sink in another house and that's about it. Apologies if my terminology isn’t on point. Is anyone able to shed some light on what the issue is here? A few weeks prior the hot water was working fine in the shower.

Happy to provide any further information if it helps.

Cheers
Dan

 

[Timmy D]

Air lock?

Take off shower head, open hot fully, then with finger over the shower arm outlet (just a pipe opening now that the shower head is removed) to block the flow of water, open the cold to force cold up the hot pipe and hopefully force air back to the tank.

Do this for 5 seconds and then test hot. Try it a few times and report back.

 

[Dan0001!`]

Hey Timmy, Thanks for your reply mate. I tried out your suggestion but still no luck. The cold water from the shower does not have great pressure (although still fully suitable for a shower), so I tried connecting a higher pressure cold water supply to the shower arm with a hose. However, still no luck.

Appreciate your time in replying mate. Any other thoughts?

 

[Dan0001!`]

Air lock?

Take off shower head, open hot fully, then with finger over the shower arm outlet (just a pipe opening now that the shower head is removed) to block the flow of water, open the cold to force cold up the hot pipe and hopefully force air back to the tank.

Do this for 5 seconds and then test hot. Try it a few times and report back.

Further to my last reply, I should mention that when following the above and attempting to flush cold water up the hot pipe, I heard a noise which appeared to come from the piping in the wall cavity.

The bath which sits adjacent to the shower was 'spitting' hot water (water, followed by no flow/, then water again) about a month ago. This rectified itself and has not been an issue since. Not sure if they're related.

Thanks again,
Dan

 

[Ben-gee]

That definitely sounds like an airlock on the bath - but it resolved itself.
The shower is probably airlocked too, as Timmy suggested, if forcing cold up didn’t work it may have non-return valve fitted somewhere.
To clear the air turn the hot to fully on and then with shower head removed use a wet vac to suck the water through, use a damp rag to create a good seal. After a while the vacuum hose should start pulsing as the water comes through - don’t stop at this point, keep sucking until it’s a steady stream. Pull the hose away and the water should continue on its own- let it flow for a few minutes until airfree, it should then work properly.
A further possibility is that the shower valve has non-return valves in it and the hot one is faulty.