Copper pipes in concrete floors?

[Matthew]

Hi All,

We moved into a 70's house last year. The ground floor is solid concrete with a bitumen layer and a top surface of wooden parquet. When we moved into the house we had an issue with one of the underfloor pipes leaking. I dug up the concrete floor, replaced the weeping joint and (foolishly) re-concreted back over the new joint. We have noticed recently that the adjacent wall was starting to look damp. I dug up the floor again and found another area of copper pipe that appeared to be leaking. How common is it to have 30 year old pipes leak inside concrete? If the situation becomes worse I may dispense with the underfloor pipes altogether and drop down in room corners from above. Has anybody else any experience with similar situations. Is it comon for copper to be corroded by concrete?

Thanks, Matthew

[Yeh But No But]

In short the concrete eats the copper. Denso tape is what you need but have a look at these 2 recent similar threads:

[Christian McArdle]

30 year old copper buried direct in concrete with no corrosion protection can be expected to be suffering general failure by now.

These days, plastic pipe is normally used (except for gas). Also, it is now common to leave the channels dug out and to just board over them, perhaps with some insulation stuffed down.

Yes, this is a common alternative solution. Ensure that draincocks are provided at the bottom of loops and that if there are any unvented sections at the top of loops, provide bleed valves there.

Christian.

[Chris Bacon]

It'll either corrode, or wear through due to movement caused by thermal expansion of an unprotected pipe. The bitumen under the parquet floor is adhesive.

[The Natural Philosopher]

I'd say it was almost guaranteed.

[Chris Cowley]

Oh buggeration. This adds another job to the ever increasing list of things I must sort out before I can actually crack on with the plumbing in my kitchen (and get the luxury of an actual working kitchen sink back).

The 3/4" copper pipes between my kitchen and downstairs bathroom would have been laid some time in the 1970's I reckon. It looks like I will mostly be digging up the concrete floor and laying new plastic pipes this weekend then. Blimmin' marvelous.

[The Natural Philosopher]

I would not bother to remove the old pipes.

Just trace em and re-route alongside.

Or re plumb the entire house.

Its been note that houses get a makeover every 15 years or so, a major refit every thirty, and a gut and replace every sixty...

However7 0's built houses seem to need the gut and replace after 30 years...

[Simon Kelley]

For interest, does anybody know the prognosis with stainless-steel pipes in the same situation? My house was built during a copper shortage in

1973, and is plumbed throughout with SS. I know that quite a few houses on the estate suffered from leaking concrete-buried pipes early on, but mine seems to have escaped that. Should I be anticpating a failure now?

The pipework is real SS, not some ersatz plated stuff, but the joints are all copper yorkshires where visible, so I assume there is at least a minimal amount of buried copper. There's no evidence of wrappings of any sort where the pipes emerge from the concrete floor.

The system originally open vented, but was converted to pressurised when the boiler was moved to the loft. This comforts me because if the worst happens then I'll get notification from the pressure gauge and the amount of water which gets pumped into the fabric of the house will be minimsed. On the other hand, the pressure (pressure vessel plus hydrostatic) at ground level is higher now than when it was open-vented. So far, the pressure-loss/time is effectively zero.

Cheers,

Simon.

[Christian McArdle]

The worst thing is that due to the 1970s copper shortage, your copper tube might be half the British Standard thickness.

Christian.

[Chris Cowley]

The hot and cold water pipes between the kitchen and bathroom are the only bits of original plumbing left from when we moved in (or rather, they will be after I've finished re-plumbing the kitchen). So this would basically complete the job of re-plumbing the entire house. I will probably just take plastic through to the threshold of the bathroom and connect them up to the 3/4" for the time being. The bathroom will have to wait.

Well, mine's a mid-1880's victorian house, but it seems to have had a big re-fit in the late 60's or early 70's (I'm guessing this would have been when the outside lav was removed and the downstairs bathroom extension added). The standard of workmanship has proven to be fairly low throughout, even by early 70's standards - clearly not DIY-ed, or if it was, then it was done by someone who just wanted to do the minimum required to sell the house at a profit.

[Chris Cowley]

Woohoo! It just gets better and better, doesn't it?

As a matter of interest - when did 22mm pipe start to be commonly used rather than 3/4" as that may help me date the existing plumbing work.

[Weatherlawyer]

The co-efficient of expansion for iron and concrete is about the same othewse they couldn't use iron to reinforce concrete. I doubt there wll be much mechanical stress. But even water will wear through pipes as the local councils and waterboards have found to their cost since they started replacing 1/2" salt glazed pipes with thin plastic accidents waiting for the day.

[TheScullster]

"Matthew" wrote

We have suffered the same fate in a new-to-us 70s house 3 years ago. But this was a hot water feed to kitchen sink in extension. The failure was a crack inside a 15mm 90deg elbow which had obviously been leaking a fair while. Many downstairs skirting boards were rotten as a result. Our ground floor was covered with plasic(?) floor tiles stuck down with black gunk, so all these were scraped up to allow concrete to dry out.

The elbow was replaced with a knee bend to reduce stress levels at the intersection.

Where the original pipes are run in concrete, they have been wrapped in a hession-like matting and bedded in sand then concreted over. So there is some allowance for movement. As noted in another post though, there is no clearance where rad pipes come up through screed.

Phil

[Capitol]

The biggest problem of that era, was not the pipe thickness, but pinholing caused by extruding pipe through contaminated dies, leading to inclusions in the wall of the pipe, which subsequently washed out. A lot of the pipes were sourced in eastern europe AIUI, so the quality standards were a bit iffy. Leaks in new houses with unstressed pipework were very common at the time (and since).

Regards Capitol

[John Stumbles]

As just about everyone has said, this will happen.

Er ... where's your gas pipework? I'd check that out PDQ.

[Matthew]

Thanks for all the info. I reassuring to think that Im not alone and the house isnt a ringer! I had assumed that leakage would only occur at the copper joints however it sounds like the pipe itself may also have small holes. I will dig the rest of the flooring up this weekend and take a look. I think for the short term I will replace the pipe and infill with dry sand. Long term I will probably take drops from the ceiling but its a major job and our house has a lot of downstairs rads so the number of drops involved would be high! I dont know how long the pipework in that area had been leaking for but it could be months and consequently the concrete is saturated. Hopefully it will dry itself out in a few days.

[nafuk]

I replaced some buried pipes and ran the new pipes behind my skirting boards.

[nafuk]

I replaced some buried pipes and ran the new pipes behind my skirting boards.

[Weatherlawyer]

So did he. So he did!

[Roger]

The message from Chris Cowley contains these words:

Don't know for sure but my late parents new bungalow built in 1968 has some imperial pipework so circa 1970 at a guess.