Plumbing - hot tap not working


24 Jul 2005
Reaction score
United Kingdom
Hot water from bath mixer tap trickles out, even when fully turned on. Has been like this for months; originally was ok then started to "howl" when water turned on & after some months stopped howling with water just trickling out.

Have 3 times used washing machine cold supply into hot supply until water flowed out of overflow in loft - didn't work. Have drained system and tried to reset all taps starting with downstairs, to find all upstairs hot taps - bathroom, en-suite and shower not working for a while, even when both header tanks in loft full. After 5 minutes started to work. I coaxed the shower hot (water was cold) to flow by sucking on flexible pipe - rather like syphoning petrol from car!

Checked mixer tap. Seems to be ok. Mixer has a shower attachment in middle. I blocked water flow with hand while turning on both hot and cold taps several times. Did not work. I removed shower attachment at tap and fixed a hose into it and connected the other hose end to utility tap whose source is mains direct. Did not work. What else could I try please?
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Hi, you "checked mixer tap" did you dismantle it ? I`ve got a feeling that the noise may have been the washer vibrating
Hi Nige F.

I took the whole plunger thing out. Nothing was loose. I left it out and turned the hot water on and it just trickled out of the hole of the mixer.
Hi; Nige F

I think I've found the problem. The hot copper pipe below the tap is connected to a brass pipe about 75mm long with some kind of bleeding nipple half way along. I took this pipe out - a struggle in the tight space - and it has a complex sprung valve system inside which is able to shut off or at least severly restrict the water flow. I plan to replace it with 22mm dia plain copper pipe. What on earth does this thing do, apart from causing a lot of bother? Does it balance the flow to other taps? Or smoothen out the flow to this tap? The Tap is connected to 22mm dia piping throughout.
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Sounds like a check(non return) valve....noise was coming from this I suspect....Is the cold side of the mixer connected to the mains water-not a tank fed supply? Only reason I can see it being there is to stop cold (if@mains pressure,going back up the hot pipework.
I think cold side of mixer is tank fed as I have closed two taps in loft tank and neither hot nor cold water in mixer is coming through. No hot water is coming through any hot tap in the house but cold taps are all working (except, as I've said, the bath mixer cold). However, I've just checked the shower and the shower hot and cold are not working either. The shower is tank fed. I wonder if the shower and bath pipes are connected? Is there any way of checking?
Only by looking and trying to work out the runs of the pipes..... Could be a connection between bath feeds and (separate) shower...All this is non standard stuff - maybe the check valve was put in when built/installed. . You said all the cold taps but the bath are on the mains....I bet the bath was too :eek: And later someone put the shower onto the bath connections...The Non return valve would have been needed once...when cold from tank. but the bath cold was changed to tank fed and the valve left there - ... . Is the shower in another room? To be correct it should have it`s own supplies..from hot cyl. and cold roof tank...But if it works ok... :)
Shower is in separate room, separated by wall/partition, and is in bedroom en-suite. Check valve was put in when house built because we have lived in it from new. But we have had not additions since then. However, builder builds many different design of houses and I bet they have standard layout with add-ons for extras like en-suite. Anyway, I'm not sure whether the design here is as good as it could be.

Have now replaced the double check valve as I didn't want to upset balance of anything. Now mixer hot water supply is fantastic :D however, I have a leak from the base of the mixer tap itself - would you blieve it! :cry: Will now switch supply off again and remove the cold 'doings' as I think its coming from there. Getting a bit fed up now :evil:
:D Mixer tap now working properly. Had to buy a new one as original faulty. The leak was due to a split in the pipe inside the tap. Have also fitted isolation valves on cold and hot pipes to make it easier to service the mixer next time. Special thanks to Nige F for advice; I appreciated your company Nige!

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