# Forum Home Renovation Plumbing  Copper and cement do they mix?

## hildahoop

I want to move the taps in my bathroom they come out of a boxed in void at the moment but I would like to move them into a concrete brick wall (the bricks are like the grey garden pavers with cement on top). is there a particular cement or render i should use? I am worried lime or something on the cement may attack the brass and copper in the tap bases and cause a leak down the track. should I paint over the fitting with something before I cement it in. Or should I just chase out the hole for the fitting and cover the lot in villaboard or similar.

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## juan

Copper embedded in concrete and/or mortar  is practically immune to reaction with corrosive alkalis, even if exposed to constant moisture. Copper will not react with dry, hardened concrete and/or mortar.  
I recently dug out some copper pipes buried for about 60 years in cement and mortar and whilst there was some discolouration there was no sign at all of any degredation of the Cu.  It will outlive you and the house so go for it. 
Cheers

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## bricks

> Copper embedded in concrete and/or mortar  is practically immune to reaction with corrosive alkalis, even if exposed to constant moisture. Copper will not react with dry, hardened concrete and/or mortar.  
> I recently dug out some copper pipes buried for about 60 years in cement and mortar and whilst there was some discolouration there was no sign at all of any degredation of the Cu.  It will outlive you and the house so go for it. 
> Cheers

  
The cement will react with the copper and the brass in your fittings. Back in the day they mixed some asbestos into the mix or alternately covered the pipes in a thin layer of asbestos paste (.5 - 1 mm) which was the same rough colour as cement/ mortar. 
The newer copper and brass are thinner and therefore more prone to corrosion

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## Bloss

Think you are wrong on that one 'bricks' - copper in mortar or concrete will usually still be there and in good condition as the building is demolished - that's why we use it! Once the cement  has cured it is pretty much inert - with slight alkalinity. See:  http://www.copper.org/applications/p..._concrete.html 
There are plenty of other sites confirming the suitability of copper with mortar & concrete. A bigger issue is to allow for thermal expansion as copper pipes expand much more than steel - so if in a weak or thin layer of mortar or concrete can cause cracking over time.

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## bricks

Not trying to start and argument here bloss, but i have always been instructed by tradesman, and by consultants to cover all copper pipes in plastic or other insulator before embedding in concrete or mortar. 
I have also seen where copper has corroded where it is in contact with concrete, ie attached to a concrete wall? 
I ahve read the website info, spose im just asking why copper re-acts to conctere surface but not being embedded in conrete/ mortar?

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## Bloss

> Not trying to start and argument here bloss, but i have always been instructed by tradesman, and by consultants to cover all copper pipes in plastic or other insulator before embedding in concrete or mortar.

  Copper pipes have been found in lime & cement mortars from Roman times - in good condition. Lots of things are done from habit, misinformation or for a different reason than the specifier says. So as I said one issue is thermal protection and interaction because of the wide differences of expansion between copper and concrete/ mortar - almost any insulation would mitigate that. 
Corrosion is simply not a significant issue in most situations where copper is used adjacent to concrete/ cement. Of course many decisions on this sort of issue are cost issues - in this case the additional (marginal) cost to add extra protection to a copper pipe or brass fitting vs the expected serviceable life of the fitting without that extra cost being incurred. Unless the corrosion is so fast and so severe that the expected life is too short relative to the rest of the structure then one just doesn't spend the extra money.  
In any case all I do is offer the evidence I am using - if others choose not to accept it that's fine. Likewise if they offer convincing alternative evidence (not just anecdotal) I change my mind (because if the facts change I must change my mind, what else should I do?). If the evidence is mixed I just make my own choice as to the most likely best option until new information shows me to be wrong - or right!   :Smilie:

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## Uncle Bob

Just another thing to throw into the mix, probably a bit off topic for the OP's question though. Having hot water copper pipes running though concrete is going to be a major heat sink.I would lag them.

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## Vernonv

> Having hot water copper pipes running though concrete is going to be a major heat sink.I would lag them.

  The thermal conductivity of concrete is very low - 1.7 W/(m<SUP>o</SUP>C) compared to 250 W/(m<SUP>o</SUP>C) for aluminium and 401 W/(m<SUP>o</SUP>C) for copper. I doubt it would act as much of a heat sink, but as Bloss has already indicated, difference in thermal expansion would be alleviated by lagging the pipe.

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## Bloss

> The thermal conductivity of concrete is very low - 1.7 W/(m<SUP>o</SUP>C) compared to 250 W/(m<SUP>o</SUP>C) for aluminium and 401 W/(m<SUP>o</SUP>C) for copper. I doubt it would act as much of a heat sink, but as Bloss has already indicated, difference in thermal expansion would be alleviated by lagging the pipe.

   :What he said:  Vernon's right. But as is now common practice (and mandated) HW pipes should be insulated wherever they are anyway.  :2thumbsup:

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## autogenous

Plumbers are advised to use 3 sand : 1 GP cement when filling around chases for copper pipe. 
Lime eats copper pipe though I think some copper pipe does come with minimal clear plastic coating to prevent this. Lagging is advised. 
If you can lag the pipe with foam lagging or grease lagging to prevent corrosion and assist in movement. 
There is some very good plastic water pipe out there these days too that hybrids with copper. 
Due to rising costs of energy I would have as much pipe insulation as possible to avoid energy loss through the pipe reducing energy bills.

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## autogenous

Placing copper in concrete is not advised these days as the associated difficulties in repair with the leaks is horrendous.  
I'm not even sure whether it is permitted to embed copper pipe in concrete floors any more for that reason. Even under the slab there is corrosion but I think there is a specific copper pipe type to go into soil.
Plumbers would know the code better. Some copper pipe comes with a plastic sleeve. 
If it is a real must Id advise a plastic sleeve so that the whole copper pipe can be removed.

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## bklooger

i lag my pipes in the wall to allow for expansion and contraction.
whilst i think copper will be ok without it i think it will burst in th long run with this ability. lagging also stops copper rubbing on jagged edges 
cheers brad

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## wonderplumb

Im a bit both ways on this. Usually I used kemlag on both H & C but sometimes only lag the hot for insulation reasons. I have pulled out copper thats been in walls for 60 odd years and it cleaned up perfect. In saying this I was always taught to cover the pipework, even if its simply wrapped in duct tape. If you are concerned use kemlag for the whole lot and tape up your recess tees, fittings etc.

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