Identifng pipe as cold water?

[Mgrant]

I am pretty sure a pipe the comes out of a screed floor, (15mm with soldered cap on it) is a cold water pipe. However no way of totally chasing the pipe to see as it is not exposed. The situation is you can see two pipe drop down in the plaster of the wall. Then under the screed of the floor 2 pipes then come up out of the screed at the other side of the room to feed the washing machine, hot and cold. Half way between this a pipe comes up though the floor with a 15mm soldered cap on it. I think it is cold water it is near were a 4 inch soil pipe exits the building. The bathroom used to be in this downstairs room is now up stairs. I guess the 15mm pipe is the old cold feed to the toilet. Any way to 100% make sure? Was going to connect on to this pipe to fit an outside tap.

 

[Mgrant]

I through running the washer and putting a screw driver on the pipe and the other end to my ear. If I hear water running when the cold fills the washer it must be the right pipe?

 

[Best]

Probably putting your ear to a screwdriver will work and, as you say, highly likely a single pipe is a cold pipe, as normally won't have a single hot pipe anywhere.
Is there no wiggle in the pipe to show movement at the pipe at other side?
I would just turn all water off and put a valve on the pipe to use to be able to turn valve on to check if water is on it when mains turned back on.
Or turn all waters off and cut pipe and blow through it to see what open tap water comes out off

 

[Mgrant]

Thanks so with all water off. If I either blow either a hot or cold tap and see when water comes out of the pipe. Or blow down the pipe and check the taps thanks. No movement in the pipe what so ever is in a solid floor screed.

 

[NickH]

All good ideas there, blow down pipe, tap with spanner etc etc.
One important thing though, never ever assume anything, ALWAYS be absolutely sure before you do anything else.
Assumption is the mother of all f##k ups.

 

[joni os]

Good advice given above. I'd just like to add, that in a property with kitchen extension etc. Don't assume stopcock under kitchen sink will isolate all mains water, especially a pipe that been capped. Make sure you can isolate in street before cutting.

 

[Stoney Ground]

You could put a temperature clamp on it as low down as possible and turn a hot tap on and se if temperature rises, then same with cold see if temperature drops.

 

[Best]

I usually blow down the open pipe to see if water comes out a tap. Keep the other tap off that you think isn't the right one. Then you should find the pipe easy to blow down with little resistance and hopefully water coming out tap.
One fear of mine is for there to be a second mains pipe from a tee below ground before stopcock unknown to me. That happened me once when I cut into a mains pipe and I had to immediately start digging the driveway at side of a house, fortunately finding an obsolete tee off.
That's why I cut a nick in a pipe with a junior hacksaw and collect the spray of water in a container while waiting to see if flow reduces. Better than pipe slicing a live pipe off

 

[drip-dry]

strange no one mentioned it could be gas...

 

[Stoney Ground]

strange no one mentioned it could be gas...

That's why I'd try to identify it with no disturbance.

 

[Mgrant]

strange no one mentioned it could be gas...

Suppose if can hear water running through while running water at the washing machine valve this would rule this out? Am I correct in saying cold water pipes usually go a darker colour then hot pipes/ gas pipes?

 

[Stoney Ground]

Cold main goes darker, if copper.

See if it was plastic that would have ruled out Gas.

Or would it?

 

[Mgrant]

Yes its copper. An it does appear darker. Like said it comes up next to a blanked off 4inch soil pipe so think it was the old toilet cold feed. Think the bathrom used o be down there. It is next door.

 

[Mgrant]

Its likely cold water. But I don't want any disasters