I've just moved in to an old house and there is a valve for a diswasher under the sink. However, I was plumbing in our DW today and I think the valve has been fitted to the rising main pipe and not the cold water supply pipe. The valve is in a great place for the dishwasher and isn't leaking, but as it is before the stop cock, I assume that I need to get a new stop cock fitted on the existing rising main pipe before the valve? Or can I just replace the rising main pipe?

Assuming you have a working outside stopcock, I wouldn't worry about it.

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Thanks guys, you've calmed me down a bit. I do have a working outdoor stop cock - I turned it off as soon as I discovered the problem!

Is the valve OK to use, do you think? I would imagine that the water pressure in the rising main pipe is a lot higher than it would be in a cold water supply pipe. I was thinking of putting in a new stopcock in the place where the current valve is, for two reasons: firstly it would take out the valve (self-cutting) which is a weakness, I think; and secondly because it would put the internal stopcock in a better place than it currently is (currently behind a cupboard). Is fitting a new stopcock a straightforward job? I've fitted compression valves in normal hot water and cold water pipes; is fitting a stop cock similar, or does it need something a bit stronger?

mains pressure will be the same.

For piece of mind fit a new stopcock by all mean, use a jointing compound on the olive.

Before you start check the pipe size is standard metric.

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Agree with all of the above.

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Your problem is now our problem

Thanks again - I'd not even considered that the pipe might not be metric. I checked it with a tape measure to see if it was 15mm or 22mm and it was 15mm, but I was just using a tape measure to check; I suppose it could well be 1/2inch. This is a bit of a noddy question, but is there a definitive way to check? Are there marks etc on the pipe that I can look out for? The previous owner doesn't know how long the pipes have been there but he was only there 2 years. So I guess I'll have to measure the outside diameter. This looked like 15mm to me earlier, but then I was only checking to see if it was 15mm or 22mm. I suppose it could easily have been the outside diameter of a 1/2 inch internal diameter pipe (which must be pretty much 15mm). If there are no markings to look for, what is the best way to distinguish 15mm from 1/2 inch? Calipers?

Is it the same pipe that goes back to the stopcock.
A clear pic and some info may help us.

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