How to tell which pipe is the mains?

[asalcedo]

I need the mains to fit a garden tap in the terrace on the first floo

of my house.

I have lifted the floorboards near where I think a mains pipe could be I see many pipes, most of them 22mm and 28mm, all of them become hot plus the mains in my house is 15mm.

There are two 15mm pipes running parallel, one becomes hot, the othe does not become very hot but somewhat hot, although I do not know fo sure if this is due to the heat of the other pipes nearby.

I have opened and closed the valve to the tank in the loft, that is fe by the mains, I cannot tell for sure if there is flow of water when th valve is opened or closed.

Other than cutting the pipe, which I want to avoid, is there a good wa to tell if that second 15mm pipe is the mains?

Wouldn't be more likely that the mains is there if there were three o any odd (not even) number of 15mm pipes?

Thanks,

Antoni

-- asalcedo

[chris French]

In message , asalcedo writes

Heating circuit and/or HW cylinder heating pipes most likely

I wouldn't expect the cooler 15mm pipe to get 'somewhat hot' really, from other nearby pipes, warm maybe. I suspect a radiator feed/supply from your description., but then it hard to tell from words.

you need to work out were the pipes are going and what they are feeding. Is there a likely radiator or sink etc.

OK to check if they are heating pipes. Find a time when the heating has been off for while. Or turn it off and wait sometime for the pipes to cool a bit. Turn the heating on, feel the two 15mm pipes, wait for the hot one to get hot first, if the 'cooler' one warms up a little while later then it's the heating return.

Well it depends on what the pipes there we doing. the feed to kitchen sink for example is normally two 15mm pipes - one cold mains and one hot

I suggest checking if you don't already what is fed by the mains supply directly - obviously the tank, normally the kitchen sink, sometimes toilets, sometimes other bathroom fittings, some sorts of showers.

Then work out where the pipes are likely to be run to these things.

[Rob Morley]

Close the isolation valve on the main cold water tank in the loft (or tie up the ballcock if there isn't a valve) and drain the tank by opening your cold taps, then close the taps again. Now open the valve/untie the ballcock and listen while the tank is refilling. Holding a large screwdriver against the pipe, and pressing your ear against the handle, can help to tell exactly where the sound is coming from.

[Dave Plowman (News)]

If you leave the kitchen cold tap running, if one of those is the mains and has simply got warm by the proximity of the heating pipes, it will become cold.

[asalcedo]

Thank you for your reply and thank you for all the other replies.

In the end, it was the mains and the tap is already in place (plant are happy).

Your tip is a great one and it is more or less what I did.

By keeping very quiet and holding my arm around a 90º bend I was abl to feel the small turbulence of the water flowing through a 90º bend Additionally there were some tiny vibrations the timing of whic coincided with the noise coming from the ballcock in the water tank i the loft.

That gave me enough confidence to cut. It was a great feeling when onl air came out!

I thought of an fonendoscope, that doctors use, but your tip is muc more practical.

Thanks,

Antoni

-- asalcedo