hot water tap 'choking'

[Dundonald]

The hot water tap in our kitchen acts strange - I can only describe it as choking. We have a combi boiler so if when I turn the hot water tap on the water isn't hot yet, the water flows fine. But as soon as it is hot or when I turn the tap on and the water is already hot the water splurts out in segments. I find if I turn the tap on quickly up to full flow the choking isn't as bad. I can hear the pipework from under the sink back to the garage rattling when the tap is choking. Very strange. All other hot taps work fine so there's no problem with the combi boiler or pipework.

I'm no plumber so I can't ascertain what the fault is, but I'm certainly willing to take things a part to see if I can fix it rather than buying new taps. Any help please in suggesting what might be the cause of the problem?

Thanks.

[Dundonald]

No one any good with taps then? :) I'll take them apart and play around see if I can spot anything. If I find the problem and if it's anything interesting I'll post back.

[soup]

Four hours from your first post asking for help to your second one. This is a newsgroup not a chat room, give people time to see think and respond.

[Weatherlawyer]

Sounds like the heater is so fierce it is trapping a lot of air. Maybe it forms steam which, on condensing, is replaced by dissolved gasses.

[Dundonald]

Soup, I appreciate that and it wasn't a criticism hence the smiley I put in my reply (that you missed out in the quote above). Chill fella.

[Dave Baker]

Is it a pillar tap with a plastic handle like the one on the right in this

a dome shaped rubber washer inside held on by a grub screw.

Same problem as my hot tap in the kitchen then. As the internals of the mechanism wear they don't open fully inside and as they heat up when the water starts to flow the thermal expansion of the brass bits and bobs closes the gap down even further. Eventually they reach the stage at which by the time you've got half a sink of hot water the flow is down to a trickle. Nothing you can do easily apart from buy a new tap. What's actually happening is that when you turn the handle the washer should pull up off its seat, like any normal tap, but in this type another bit that wears start to float down instead leading to very little net motion. Feckin' stupid design basically.

I'm an engineer so I modified mine slightly on the lathe to increase the range of motion to tide me over until the new kitchen goes in but most people won't have that option.

If it's not that kind of tap ignore all the above.

-- Dave Baker

"Why," said Ford squatting down beside him and shivering, "are you lying face down in the dust?" "It's a very effective way of being wretched," said Marvin.

[Dundonald]

I came on here to post that I had decided to swap the valves around - i.e. cold valve in to hot tap and visa versa. Works a treat now.

But thanks for your post - different tap but same valve type by the looks of those pictures.

[John Rumm]

Does your combi include some form of flow regulation (i.e. so that it prevents the water from running cool should you ask for it faster than it could heat it otherwise)?

I have seen a similar thing happen with an old multipoint water heater.