Copper pipes in screed - gas and water

[a_seth]

Help!

I've had a plumber in who installed a new boiler. As part of this he had to get the gas and radiator pipes to a different part of the house (15mm and 22mm copper pipes). His chap said they should go in the floor of the kitchen as that's where the water pipe was (15mm copper). So he basically (from what I can tell) he bashed out a 3/4 inch section of screed to expose the water pipe (which seems to be covered in something hairy?!) and put all the new pipes together in the trench (about 4 inches deep).

The plumber has since gone, and I'm busy trying to figure out how to fix the hole in the floor! I've read different things, copper may or may not be attacked by screed, it would probably be better to cover the pipe with conduit/denso tape/plastic/insulation.

The problem with covering the hole with ply is that it is right up against the wall (nowhere to attach the ply to). So you know this is about 1m of copper in all, and it does have a few joints in it.

Really any advice on how to sort this out (hopefully without getting someone in to cut out the pipes) would be appreciated.!

 

[Diyisfun]

Cover the pipe as you have said & fill trench with sand/cement

 

[Doggit]

Copper will be attacked by the acid in the cement, but I've seen copper that's been in cement for 10 years, and nothings happened to it. But it's best to play safe, and insulate and protect the pipe. You can use pipe wrap to stop any acid erosion, or if there's enough space around the pipes, then use pipe insulation instead. This is the best option, as it'll also save heat being lost into the floor slab. Do you know where the DPM is, under the slab, or on top of it - in which case, you'll need to blackjack under the pipes, and then recement the pipes in.

 

[dilalio]

Duct tape around the pipes so that it wraps round to underneath and then foam insulation if room or felt lagging if tight for space - you'll have to split the lagging longways, open it up and wrap round the pipes with more duct tape to hold it in place.

 

[denso13]

Normal mortar or concrete won't affect the copper but cover it as suggested above to let it move (expansion/contraction).

 

[a_seth]

Thank you so much for getting back to me on this everyone - at least it doesn't sound like it's too much of a disaster then given your replies!

Bit worried about just using duct tape - it seems a bit flimsy but I suppose with this felt stuff it should be ok?! Is there anything else I should wrap around that is designed for this, or is it just duct tape?!

Not sure where the dpm is, knowing these guys they might have gone through something and not told me?! should I do something to be safe than sorry?

I have some cement, and a bag of sharp sand - is that going to work? What sort of ratio do I need for this?

Again many thanks for all the replies.

 

[stevehit]

I hope the joints are soldered, or you have a disaster waiting to happen...

 

[Agile]

The copper will be attacked if the cement stays damp.

Generally for compressive loads when filling small areas above pipes a weak mix of 1:8 with soft sand is adequate.

 

[dilalio]

Duct tape is purely to stop the lime in the cement reacting and corroding the copper - it's great when space is tight!

 

[Doggit]

Bit worried about just using duct tape - it seems a bit flimsy but I suppose with this felt stuff it should be ok

All the duct tape is doing, is stopping the acid in the cement from getting to the copper pipe, felts good if you've cut a hole through cements that already set, but if it's still wet, then it can carry the acid through it, but if you can't get some insulation around any heating pipes, then you risk heating and cooling the floor, and losing heat from your system, but if you can't get any pipe insulation in, then use the felt, and cover it with the duct tape.

Obviously, you'll only get the lime in a ready mixed bag of mortar, not in cement.

You can use the cement and sharp sand if you want, and 1:5 is fine, or 1:4 if there's going to be a lot of traffic over it. Remember to dampen the old cement first, or pva it with a 1:3 mix to stop the water being sucked out of your mix when you drop it in.

 

[Steelmasons]

The copper will be attacked if the cement stays damp.

Generally for compressive loads when filling small areas above pipes a weak mix of 1:8 with soft sand is adequate.

1:8?..WTF did you get that from?????.....lime is what attacks the copper..
1 in 8 mix FFS..soft sand??..jeez.

 

[Steelmasons]

The copper will be attacked if the cement stays damp.

Generally for compressive loads when filling small areas above pipes a weak mix of 1:8 with soft sand is adequate.

What planet are you actually on FFS???

 

[Doggit]

Well blow me down with a feather covered chicken. My apologies to Dilalio, and my thanks to Steel. It's always struck me as odd, that having been told continually that the acid in cement attacks copper, I've never seen the evidence in pipes I've taken out of cement. So following Steels comments, I checked up on the Copper associations website, and it seems as though you cover the copper to protect it from damage caused by thermal movement.

 

[denso13]

it seems as though you cover the copper to protect it from damage caused by thermal movement

Quite, is there an echo in here?

 

[dilalio]

OP can always wrap them in Denso tape, eh @denso13