Upstairs basin cold taps running slow

8 Nov 2016
Reaction score
United Kingdom
2x bathrooms upstairs. Both basin cold taps suddenly running very slow. Bathroom hot taps run OK, bath cold tap runs OK (maybe a bit slow), all downstairs taps fine.

I checked the cold water tank in the loft and the water level is nearly up to the top.

Any ideas? what is weird is that it has affected both the cold basin taps only

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OK, I just went to have a shower and nearly burnt myself because hardly any cold is coming out there too. So it looks like it is all upstairs cold water...
Is it mains pressure or gravity supply?
A slow flow on a mains fed cold could indicate a burst pipe somewhere. Doesn't have to be a burst inside, it could be burst underground in the garden, but then you may also notice the cold kitchen tap running slow. You can check this at the water meter.
If it is a gravity fed cold tap supply, then the outlet at the bottom of the loft header tank could be blocked up, or an air lock in the pipe. The cold header tank can scale up with limescale that can close off/block the supply to the taps.
As in my original post, downstairs cold water is fine. I'll check the loft tank for blockages next
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Further investigation: the downstairs loo basin cold is also slow. The slow ones all seem to be fed from the same exit pipe from the cold tank. No obvious blockages going into the outlet, though, and as I say it's happened all at once, not gradually :(
So... Looks like an airlock. I turned all the offending taps on full and after a couple of minutes slower flow and some spluttering the 'seem' to be back to normal service
What does the inside of the cold water storage tank look like? How old, is it an old steel tank that's rusty, plastic with loads of scale build up. Is it covered? Could something have fallen in it and blocked the outlet.
If something has gone into the pipe there is a possible fix.
Shut off all cold taps. Connect a hosepipe from mains pressure tap to one of the taps. Open that tap, then turn on the hose. Basically fill the loft tank from a hose pipe.
The mains pressure should push back any block into the header tank, and clear air lock if that is a problem.
Don't over do this, you are only pushing a small amount of mains pressure up the pipe, you don't want to leave it running long as the flow could be greater than the overflow can handle. You don't want to flood the loft. Have eyes in the loft while you do it.
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Plastic tank, covered, clean inside. If the problem recurs I will try the hose back up the rap thing.

I had the same problem as humbughumbug. Tried opening all the cold taps, lots of gurgling but no joy. Tried stevethejoiners tip, worked a treat. Thanks mate.
Hi .. same problem here. Luckily tried the all taps on fix and flow has returned to normal. But overflow is dripping outside house, so I guess I need to get in the loft and take a look

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