Tried to do plumbing but failed

[PenguinWithHair]

*****
Moderator's note
amalgamated two threads
*****

I'm trying to fit an electric shower, I thought I'd fit an iso valve to the shower feed which is from the mains. I know this because the shower goes cold every time someone else uses a cold tap which is also from mains.

So I turn the main stop cock off, and leave the cold tap on in the kitchen running until it doesn't run anymore. Hopefully the water in the pipes upstairs is all drained out right?

Using a pipe cutter I cut the copper pipe I think is the shower feed so I can fit a valve, WATER GUSHES EVERYWHERE MASS PANIC WHAT AM I GOING TO DO! I panic for a few seconds and stick my thumb over the pipe and manage to stop the water with my thumb. I manage to scrabble together my valve and tighten it on.

Please help me, what have I just done! The cold taps of the bath and bathroom sink are gravity fed from a tank in the loft but they are still running so I'm not sure if it's water coming from there otherwise those taps wouldn't work right? Have I just cut into a central heating pipe? I've bleed the upstairs radiators and they hissed for a few seconds before letting water out.

Please help, whatever pipe this is I've cut into, will an isolation valve be ok left on or shall I call a plumber to couple it together?

Many thanks.

 

[Newboy]

shower goes cold everytime someone else uses a cold tap which is also from mains

You would expect the opposite - if somebody opens a cold water mains fed tap then the flowrate to the shower would usually fall and the temperature increase.

Hopefully the water in the pipes upstairs is all drained out right?

Only if you open other outlets higher than the kitchen tap.

Have I just cut into a central heating pipe?

Possible but unlikely given the location of the pipe

will an isolation valve be ok left on or shall I call a plumper to couple it together?

Given that you've used a cheap iso valve and used PTFE tape on the threads then I'd be inclined to get somebody professional in to repair the pipe

plumper

I wouldn't call a plumper - a plumber may be more useful

 

[john4703]

If you have fitted a valve and left it on then that should complete the circuit if it was a central heating pipe.
You can check if it gets hot when the heating is on, remember it might be a feed to heat the hot water so check that as well.
Probably no need to call a plumber.

 

[PenguinWithHair]

Ok so the shower heat turns itself off when the water pressure drops from someone else turning on a tap, it's a mains fed electric shower. Also thanks for pointint out my spelling error.

I'm not having a go here, I'm looking to be educated, what's wrong with a cheap iso valve and using PTFE tape on the threads, isn't that what you're supposed to do? Should I but a more expensive valve and not use PTFE tape?

 

[PenguinWithHair]

Thanks for the reply, I've had another reply on another thread saying I should call a plumper because I've use PTFE on the thread and a cheap valve. Can I have some feed back on that please, aren't you supposed to use PTFE tape on the threads? (Fair enough I'm a little messy with it)

 

[PenguinWithHair]

I have now rejoined the pipe together using the valve.

 

[JohnD]

PTFE tape is great if you use it on a seal. The seal on your valve is the brass (or copper) olive that should be a close fit into the recess in the valve, and if for some reason it is a poor fit, you can wind tape on it to improve the seal by taking up excessive clearance. It is widely used on certain screwed joints. Older plumbers used to use paste. There are gel sealants these days.

Plumbers have very high aesthetic standards and like nothing better than to criticise inelegant work, especially PTFE tape that is visible on screw threads of a compression joint, where it does no good. I am not a plumber so I don't mind what you do, as long as it does no harm.

Unfortunately there are cheaply made isolation valves, often sold for less than a pound, where the quality is so poor that they sometimes leak for no reason whatsoever. I've taken to using Pegler valves now, with a little lever so you can operate them with your fingers. They allow better water flow, and hardly ever leak.

BTW, if you were able to stop the water gushing out with your thumb, it was not at mains pressure. Either it was remnants of water trapped in the pipe, or it came from a water tank, probably in the loft. Follow the pipe and see where it goes.

 

[Hugh Jaleak]

Cheap valves tend to leak the next time you want to use them. PTFE tape is where a joint is made using a male and female thread, the fitting up have is known as a 'Compression' fitting. Tightening the nuts compresses an 'olive' to make the joint, the threads allow the joint to be tightened, they dont actually make the seal.

 

[PenguinWithHair]

Right ok thanks, so I've put the tape in the wrong place. Lesson learned. Is it going to do any harm it being on the threads or I leave it?

 

[john4703]

Compression fittings should be fine without and PTFE tape or compound. If you used it on the threads it should be fine, (some people manage to put PTFE tape under the olive which in my opinion is not good). A cheap valve will propably be fine as you will not be turning it on and off frequently.
If it is all dry and no sign of a leak leave it as it is.

 

[PenguinWithHair]

Ok, thank you. I'm starting to calm down now I got quite stressed out.

 

[PenguinWithHair]

Also thank you Moderator for joining the two threads I was in a bit of a panic and wasn't sure where to post.

 

[Newboy]

Plumbers have very high aesthetic standards and like nothing better than to criticise inelegant work, especially PTFE tape that is visible on screw threads of a compression joint, where it does no good.

Not only does it do no good, it's the wrong way to install a compression fitting and it can do harm by preventing the fitting being tightened correctly - nothing to do with aesthetics and everything to do with doing the job properly.

 

[muggles]

If you've managed to stop the water with your thumb, then you've cut into a tank fed pipe. You wouldn't normally be able to hold back mains pressure.

The valve you've used only has a very small internal bore, and particularly on tank fed supplies will severely restrict the flow through the pipe. Full bore valves are always preferable

 

[heatservice]

As you had turned the mains off and you kitchen tap had stopped running I suspect you cut the right pipe but the water was just that which remained in the pipework feeding your tanks in the roof space etc, had you turned the hot taps on for a short while to make the ball valve drop and let air in it would have most likely drained. Now you have reconected your pipe & turned the water back on, does the new valve isolate the shower flow when you turn it off? PTFE tape is not required on compression fittings but dont worry, Ive seen (so called) professionals do it. As said by others, you might think about replacing the isolation valve with a full bore lever type one if you prove it is your shower supply.