Burying copper in plaster ?

[fagent3]

Hi,

I plastered over a short 4-5 foot length of 10mm copper water pipe, and coverd with tiling (electric shower).

Now a tradesman has told me that you shouldn't plaster over a copper pipe, as the plaster will react and corrode the copper.

I'm not keen on digging it back out (although I do have spare tiles) , but if it's likely to cause a potential burst in the water pipe pipe buried in the wall, I'd prefer to re-do it with the pipe in a plastic conduit/hose.

-- Is this true ? .. will plaster corrode copper ?

-- If it does :(( - any idea on how long it'd take ? It's been in the wall for 2 years and I'd be happy to leave it well alone if it'd take >10 years to corrode through.

-- If it were to leak, would I be likely to detetc it at the bottom of wall behind the bath pannel ?

Any comments/advice welcome.

-- Hammy

[The3rd Earl Of Derby]

You've already done it,its been there for two years,you want to redo it.

Wait till it happens, if it happens?.

-- Sir Benjamin Middlethwaite

[EricP]

Denends where you bought the pipe. If it's a shed's eggshell thin one then keep a mop and bucket handy, if it's decent X stuff from a plumbers merchant, then it could last years.

[sm_jamieson]

I think it could eventually. I bet it would take many years. I always cover cold pipes in tape (e.g. PVC insulating tape), and 15mm hot pipes inside a 20mm plastic conduit to allow for expansion. Simon.

[nightjar]

Yes. You should always wrap copper tube in Denso tape, to protect it, before burying it in plaster. Putting it inside a plastic tube and plastering over that also works, but is not so professional.

That will depend on how heavy a wall thickness it has, but you could already be close to having problems.

The path that water takes when it leaks is notoriously unpredictable. Your first indication could simply be a large bit of plaster falling off the wall, with tiles attached.

Colin Bignell

[sm_jamieson]

I thought the main problem was with concrete and copper, where denso tape should always be used. Is plaster as bad as cement ? Also, can any scientist tell us how the corrosion occurs ? Simon.

[Ian_m]

I think the corrosion occurs at impurities in the copper. Damp + impurity causes electrloytic reaction and a pin hole leak occurs. My mate had it with his 70's house with the copper central heating pipes in concrete floor leaking. Cut pipes out with angle grinder replaced with 15mm copper in 22mm plastic (not so messy as Denso tape).

[sm_jamieson]

So its not the plaster, its the damp. And after the plaster has dried there's no more problem. Hum. Must be more to it. Simon.

[Rob Morley]

Then clear up the mess made by the leak, redecorate downstairs ...

[The3rd Earl Of Derby]

Yup! in ten years time. maybe,maybe not?

-- Sir Benjamin Middlethwaite

[sPoNiX]

There will still be a certain amount of moisture in 'dry' plaster.

sponix

[manatbandq]

So it took 20-30 years if this was a recent problem?

MBQ

[daddyfreddy]

I always believed cement and copper were a problem because of the lime in the cement reacting. I didn't know plaster was a problem. I've also heard of problems with concrete buried pipes installed 30 odd years back. AFAIK, the real issues of corrosion are near the entry and exit point of the pipe in concrete. Also, considering the amount of lime and all other impurities in your water supply, copper pipes have a limited life in any case. If I was the OP, I wouldn't be too worried.

[The3rd Earl Of Derby]

Hmmm! I'm a bit confused over this as well. My mother lived on an estate and the gas pipe was buried in concrete leading to the kitchen from the meter in a cupboard behind the front door,

3" deep it was...I know this because I drilled through it in the floor. lol

-- Sir Benjamin Middlethwaite

[Dave Jones]

Nope get insurance out and get downstairs and bathroom completely redone.

[Michael Chare]

I covered a some short lengths of 10mm pipe with some gooy tape to avoid corrosion problems. Hot water in the pipe then made the goo melt and it dripped!

I surrounded the pipes with bath/kitchen sealant - to avoid expansion problems before tiling over. Maybe less corrosive as well.

It is probably better to the matter sooner rather than later. The must be many pipes that pass through plaster ceilings that have no yet corroded!

You could make a test rig by burying a short length of pipe in some plaster and then inspecting it at a later date.

[John Rumm]

There will be even more "moisture" inside the pipe I would have though... and that damp does not seem to be a problem! ;-)

[daddyfreddy]

I've bought from sheds and plumber's merchants and never noted any difference in the thickness of the copper.

[nightjar]

Unless you live in the Chilean desert, dry plaster still contains moisture.

Colin Bignell

[Dave Fawthrop]

| I've bought from sheds and plumber's merchants and never noted any | difference in the thickness of the copper.

It is all made to the same British Standard.