Low rising main pressure - Help, please!

Hi all,

I've just installed a new sink in the kitchen. To do so, I obviously needed to turn the main stop cock (in the street) off. I've now turned it back on and the sink taps work fine - bags of pressure.

However, last night when filling up the bath, the flow of cold water stopped. I got up into the loft, and found the cold water tank had run dry, with the nozzle of the ball valve barely trickling.

My thoughts/findings so far:

1. Air lock - My first thought, but surely if this was the problem, as soon as the ball valve opened, the high mains pressure would force the air out no probs?

2. Knackered ball valve - Doubt it. The header tank takes a feed off the same pipe as the cold water tank. When I push the ball down, it suffers from the same problem - very low pressure. It's almost inconceivable that both the ball valves would have gone simultaneously, isn't it?

3. Crud in the pipes - Very unlikely that there'd be a big enough build up to impede mains pressure - surely?

Any ideas? I'm hoping I'm missing something very simple!

Many thanks in advance,

Rob

strip the ball valve down prob muck in it

Agree with Gordon. Option 3 Not inconcievable and not unlikely

Thanks, I can try that - only hesitated as it's got to be pushing 40 degrees up there!

Is that really the only obvious explanation?

Is an air lock simply impossible on the rising main?

robmorgan said:

Thanks, I can try that - only hesitated as it's got to be pushing 40 degrees up there!

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Tell us about it.

Is that really the only obvious explanation?

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I think that you know it is.

Is an air lock simply impossible on the rising main?

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Yes, except at the top of a house at the top of a very tall hill in a very hilly locale that's a long way from the pumping station, and your pipes go up and down a lot before reaching the cistern.

Right. I turned off the stop cock on the rising main feed to the header tank - for some reason there isn't one for the main cold water tank. I took off the ball valve and tested the flow - bags of pressure.

So, as youse suggested, the ball valves must be crudded up, so I'll clean them out - thanks!

One more thing - where I've been testing the rising main by squirting it into the header tank, it's stirred up all the crud at the bottom, and it's generally looking pretty filthy. Is this a problem? Do I need to drain and clean it? Or is it OK to have it swilling round the central heating system?

Just look up powerflush in the sticky and release ww111 PS. if you`re S london , not too central ....a M8 in Guildford will do a reasonable£ powerflush and a thorough job.

It worked! The ball valves were indeed crudded up.

DIYnot.com to the rescue again! Thanks a lot for your help.

robmorgan said:

One more thing - where I've been testing the rising main by squirting it into the header tank, it's stirred up all the crud at the bottom, and it's generally looking pretty filthy. Is this a problem? Do I need to drain and clean it? Or is it OK to have it swilling round the central heating system?

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No, it isn't ok - depending on the degree of filth, it could be a problem waiting to happen on two counts:

1. If you have sludge and rust then your system is corroding.
If it doesn't have any chemical inhibitor in then it would be expected to corrode. However, don't add any inhibitor without flushing out the system first.

2. If you have sludge and rust in the system then it can clog valve, pipework and your boiler.

Now is an ideal time of year for flushing!

BTW, you should put the system contents down the toilet, not on the garden, so that it enters the sewer and ends up in a treatment works rather than a local stream or pond.