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Post by crowsfoot on Jul 1, 2021 7:57:02 GMT
I haven't been to this job myself yet, however, 4 different plumbers have (including my workmate).
After an initial burst of hot water from the hot kitchen tap it then stops flowing,however, if you then open the kitchen cold tap the hot water tap then starts to flow again.
My mate decided to put some new kitchen taps on (which hasn't made any difference to the problem) and whilst the taps were disconnected he tested the isolation valves for flow and both had a decent flow of water.
The tenant said that all the other taps in the house work alright.
It's an unvented set up.
I'm down to take a look at it next week, but at this moment nothing makes any sense and nothing fits together any ideas anyone?
Will post back next week after I've had a look.
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Post by endfeed on Jul 1, 2021 10:24:10 GMT
Non return valve on hot water pipework playing up maybe?
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Post by dickpuller on Jul 1, 2021 10:41:41 GMT
Ah, it’s the old Flow is the same as Pressure thing.
A partially turned off valve, blockage… etc will pass(flow) water through so much & pressure will build. Turn the tap on & it displaces that pressure. You do not have flow, only displaced pressure.
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Post by crowsfoot on Jul 1, 2021 15:55:53 GMT
Both sound good to me, I was thinking along the lines of a blockage and possibly the filter at the pressure reducing valve. I'm quite sure my workmate said it was a sink mixer that he renewed last week so the balance pressure v flow rate seems a good idea to me. I'm almost looking forward to getting back to work to have a go at this one!!  Thanks all and if anyone has anymore ideas on this one please let me know them. |
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Post by battle1066 on Jul 1, 2021 17:25:23 GMT
Since so many twiddlers have been and gone I would go back to basics and make sure all the valves as are open and the pressure relief is at the correct setting.
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Post by rocketmanbkk on Jul 3, 2021 7:15:05 GMT
I had tons problems with the flat that I rent out.
It’s was quite a few years ago & I got my mate out.
The multivalve was blocked with black shit. Gave it a good clean & it was ok but happened again soon after.
It needed a new multivalve
It’s worked since
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Post by crowsfoot on Jul 6, 2021 19:03:23 GMT
Had a look at the tap today and made the video of it as promised.
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Post by dickpuller on Jul 7, 2021 5:19:47 GMT
Small blockage in the Hot Pipe. When the cold mains is turned on, the back pressure forces the blockage back into the pipework, letting the hot water pass over it. Turn off the hot tap, the pressure is only behind the blockage, so blocks the pipe again.
Could be old cylinder foam, a bit of lagging......anything!!
Replace the pipe to the Kitchen hot tap, right back to the HW pipe tee👍👍👍
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Post by crowsfoot on Jul 7, 2021 6:31:33 GMT
It's a good un in't it?
Here's what we did yesterday and it's all so typical of part of a day doing plumbing repairs:
We first decided that a good point to start with was at the pressure reducing valve which came out in bits!
So it was off to the merchants for a new valve and at the same time we thought to fit a gauge so that we could see exactly what was happening to the water pressure when the hot tap is opened in the property (it was effecting all hot taps).
(NB Pressure reducing valve is fitted on the mains just before the mains enters the cylinder thus protecting the unvented cylinder from any excessive water pressures that could occur during the night when less water demand is on the main).
The result being that the puzzle seemingly had been fixed (the hot tap now doesn't stop running when turned on).
There's still a problem though, the stood pressure (that we adjusted to 3.5 bar) (static?), drops down to almost zero on the gauge we fitted (dynamic pressure) when any hot tap is run.
We then checked the internal mains stop tap - just in case it wasn't fully turned on (it was).
A look for the boundary stop tap which couldn't be found and looked to me as if it's been tarmacked over as many have.
End of our job for now because we've now passed it onto the local water authority to find and then check that their stop tap is not restricted.
Moral of the story is if you've got low water pressure the last thing you need is an unvented cylinder - fit something else!
If I get to know anything more on this job I'll post up and at least the old girls hot tap now as a constant flow to it which I'm sure she's happy about.
Tappy,
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Post by DIYDafty on Jul 7, 2021 13:52:36 GMT
... Moral of the story is if you've got low water pressure the last thing you need is an unvented cylinder - fit something else! ... Out of interest what do commercial buildings have fitted? Can they have vented? What if they are in a low pressure area? I'm thinking office blocks, hotels etc. |
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Post by crowsfoot on Jul 7, 2021 16:15:18 GMT
The modern thing would be a low level mains storage tank then a pumped mains supply to each of the commercial units, it's all about supply at times of peak usage.
A storage cistern at high level then gravity feed to the commercial units is a more out dated method dd.
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