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Thread: Copper tubing in slab

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    General Contractor dx's Avatar
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    Default Copper tubing in slab

    Currently renovating a house on slab, which is uncommon in my area. Copper tube plumbing in the slab. It looks like we may have a leak in the hot water tubing, but my plumber is still testing.

    1. Does copper in a concrete slab deteriorate with time? Does the concrete cause it to corrode? Is there an "expected life span" for copper tubing in concrete? Any studies done on this?

    2. If we find that we have a fault/leak in the slab, is there any specialized tester or procedure to locate it?

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    DIY Senior Member Runs with bison's Avatar
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    The only experience I've had with pipe leaks under the slab was a 90 on a very long hot water run (fraternity house long ago.) It was easy to find the leak because the floor was toasty above it. It had also leaked there before apparently as some joker put a toy boat in the fill material. It floated to the surface as we were digging/bailing.

    The problem in that case was probably either erosion of the 90 and/or cracking from flexing/vibration of the 90 due to thermal expansion/contraction of the very long run. I can't remember if the leak was on the outside or inside of the 90...it was one of the two. I've learned a few tricks since then so if I was doing it today I would: enlarge the line at the bend to reduce velocity/erosion, use a long radius 90 if possible...or use two 45's to reduce the energy and stress at the joint. Another possibility would be putting in a tee with flow through the branch and an end cap. That way the eddy in the dead end would prevent the impingement/erosion problem.

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    General Contractor dx's Avatar
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    This is tubing, not pipe. So yes, I'm sure it has generous radius 90s

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    In the Trades Gary Swart's Avatar
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    Concrete eats copper. That's why in my opinion, it should be against codes to bury copper in concrete. It's not a question of if there will be a leak, it's when it will happen. And, repairing a leak won't end the problem.

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    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by dx View Post
    This is tubing, not pipe. So yes, I'm sure it has generous radius 90s
    Don't be so sure. I'm talking about the K,L,M tubing that resembles pipe and often is referred to that way. When I think of tubing I usually think of the light coiled stuff. Anyway, sorry I commented on it, you obviously don't need my input.

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    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    Quote Originally Posted by dx View Post
    Currently renovating a house on slab, which is uncommon in my area. Copper tube plumbing in the slab. It looks like we may have a leak in the hot water tubing, but my plumber is still testing.

    1. Does copper in a concrete slab deteriorate with time? Does the concrete cause it to corrode? Is there an "expected life span" for copper tubing in concrete? Any studies done on this?

    2. If we find that we have a fault/leak in the slab, is there any specialized tester or procedure to locate it?
    In my area a house on a slab is very common as are leaks in copper under the slab. When confronted with leaks under slabs we have people in the area to locate and expose the leak. It's a bit pricey but they find it within 6", and make a temporary repair. We then make the repair needed and re cement the opening in the slab. In most homes the copper latest 20 to 25 years, it's type L tubing and it is looped so all joints are in the walls not under the slab. I have seen some leaks in homes 5 yrs old. The copper is sleeved where it penetrates the concrete.

    John

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    Moderator & Master Plumber hj's Avatar
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    Default copper

    The majority of copper leaks, unless you have agressive water, is caused by the installers kinking the tubing where they bent it to rise through the floor. Instead of discarding the tubing they left it in place. The leak is usually in the hot water line because the heating and cooling cause the kink to flex, and just like bending a piece of metal back and forth often enough, it causes the tubing to crack. The first step that I tell customers is to contact your homeowner's insurance company to see what coverage you have. Normally, unless your company is Allstate or similar who require that the leak be damaging the carpet or house contents, they will cover the cost of locating, accessing the leak, and repairing the floor, minus your deductible. The actual leak repair, which is usually very minor, is not covered. What do you mean by "the plumber is checking for a leak"? It only takes a few minutes to determine IF you have a leak. Finding where it is can take time unless the floor is getting hot at that location or you hire a leak detecting company. As far as the hot floor is concerned, I once repaired a hot water leak in an apartment, and the girls complained afterwards that they did not like the cold floor. They though having a hot floor was a perc of living on the lower level.
    Last edited by hj; 10-09-2009 at 06:21 AM.

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    General Contractor dx's Avatar
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    Thanks all.

    hj, without going into a lot of detail, this is a whole-house renovation and the hot water lines were abandoned by the previous owner (a diy wannabe) who installed mini electric water heaters at each point of use. It is a jumbled mess and my plumber is ripping out all the mickey mouse above-slab piping. There is no water heater yet, we're just sorting it all out.

    It appears that the hot water tubing in/below the slab is not holding pressure (testing with air), but we have to make sure we capped tightly all the end points. It does not appear to be looped, just 3/4" line going in the slab and 1/2" lines coming out at each bath, kitchen and laundry.


    The cold water tubing in the slab is working fine and holding pressure. House is about 60 yrs old.

    Gary Swart, I'd like to see where you got your information that concrete eats coper. These people disagree with you:
    http://www.copper.org/Applications/p..._concrete.html

    It is also acceptable to run a copper water tube through a concrete floor or wall, provided that allowance is made for the lateral thermal expansion and movement of the tube and protection of the tube from abrasion. This can be done by insulating the tube where it passes through the wall or by wrapping the tube with an approved tape (to avoid abrasion) and installing it through a sleeve. Please refer to your local plumbing code for specific requirements regarding the protection of pipes and tubes passing through concrete and masonry floors and walls.

    copper should be protected when it comes in contact with concrete mixtures that contain components high in sulfur, such as cinders and fly-ash, which can create an acid that is highly corrosive to most metals including copper.

    Plumbing codes require protective tape around the pipe where it meets concrete, but yes, if you provide a wrapper around the pipe, then you can inbed it.
    Last edited by Terry; 10-09-2009 at 10:13 AM.

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    DIY Junior Member TomD's Avatar
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    Quote Originally Posted by dx View Post
    Currently renovating a house on slab, which is uncommon in my area. Copper tube plumbing in the slab. It looks like we may have a leak in the hot water tubing, but my plumber is still testing.

    1. Does copper in a concrete slab deteriorate with time? Does the concrete cause it to corrode? Is there an "expected life span" for copper tubing in concrete? Any studies done on this?

    2. If we find that we have a fault/leak in the slab, is there any specialized tester or procedure to locate it?
    Concrete is aggressive to copper. A proper installation should have the copper wrapped in something that provides a separation between the two.

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    General Contractor dx's Avatar
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    Quote Originally Posted by TomD View Post
    Concrete is aggressive to copper. A proper installation should have the copper wrapped in something that provides a separation between the two.
    Tom, I've heard that opinion from several people, but so far no one is able to back it up with any data. Only hearsay. If in fact concrete corrodes copper, there must be a study somewhere to show it.

    I repeat, the copper association says it's fine. Any data out there to show that's not true?

    http://www.copper.org/Applications/p..._concrete.html

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    Master Plumber master plumber mark's Avatar
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    Talking you are nuts...

    Quote Originally Posted by dx View Post
    Tom, I've heard that opinion from several people, but so far no one is able to back it up with any data. Only hearsay. If in fact concrete corrodes copper, there must be a study somewhere to show it.

    I repeat, the copper association says it's fine. Any data out there to show that's not true?

    http://www.copper.org/Applications/p..._concrete.html
    you dont know what you are talking about

    copper is good, but will go bad if installed incorrectly under concrete...

    I have installed copepr under concrete hundreds of times, in hundreds of homes but I install the rubber aramaflex sleeves over 100% of the copper.. to protect the copper....

    most problems happen becasue they just lay the copper directly into
    the pee gravel and the compression and contracton of the plumbing
    system over time cuts the copper pipe....usually where it goes up through the concrete
    .
    no one cares to spend the extra 100 bucks to totally protect the pipe
    and the copper can still last decades without any protection on it...

    its simply a fact of life..



    Mr DX..................
    if you were wise, you would nip it all in the bud right now...

    tell your plumber that you want the whole house renovated and you
    want all new pipes run overhead and dropped down to the fixtures,
    and everything in the concrete abandoned...

    if you dont just do this, it will eventually break in other places
    after you move in , and it will cost you a whole lot more
    over and again and over again....

    .make it right while it is still cheap to do.......

  12. #12
    DIY Junior Member TomD's Avatar
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    Quote Originally Posted by dx View Post
    Tom, I've heard that opinion from several people, but so far no one is able to back it up with any data. Only hearsay. If in fact concrete corrodes copper, there must be a study somewhere to show it.

    I repeat, the copper association says it's fine. Any data out there to show that's not true?

    http://www.copper.org/Applications/p..._concrete.html
    I've worked in the construction business for 30 plus years. I've got a civil engineering degree from one the the most respected engineering schools in the world. That said, I make my living as a construction engineer/manager in an industrial environment and don't perform any design work, per se - only make sure that contractors install what the design engineers put down on paper.

    Look at the fifth paragraph in your link. The Portland Cement Association says that some ingredients in some mixtures can help form an acid that is corrosive to copper so infer from this article what you wish. A huge majority of the concrete batched in the area of the country in which I've worked all of my life contains the exact ingredients the PCA warns against. Even if you requested that these ingredients not be included in the batch you order, if it not a prudent assumption that that batch won't contain some of those ingredients.

    All of the design engineers that I've worked with over the years (and I've worked with some of the largest and most respected, again, in the world) and when they decide that a copper tube/pipe needs to be within concrete (admittedly a rare situation and is generally an avoided practice) they also specify that copper pipe be separated from the concrete. Heck, even the residential building codes around here require that copper water pipes in slabs on grade be wrapped in a plastic sheath.

    Again, you be the judge. Concrete can corrode copper.

  13. #13
    Moderator & Master Plumber hj's Avatar
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    Default copper

    In the 60's, when I was in Chicago, we installed many copper radiant heating systems. The copper was imbedded in the concrete to give proper heat transfer WITHOUT any shielding. I have seen old systems in this area the same way, and they do not have "corroded" copper lines.

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    General Contractor dx's Avatar
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    Quote Originally Posted by master plumber mark View Post
    tell your plumber that you want the whole house renovated and you want all new pipes run overhead and dropped down to the fixtures, and everything in the concrete abandoned...
    Yes, we're considering this, but in our climate freezing is a factor. Outdoor ambient can get below zero F at times and with a vented attic it is difficult to insulate the pipes well enough so they won't freeze.

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    Master Plumber master plumber mark's Avatar
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    Talking use Wirsbo PEX

    Quote Originally Posted by dx View Post
    Yes, we're considering this, but in our climate freezing is a factor. Outdoor ambient can get below zero F at times and with a vented attic it is difficult to insulate the pipes well enough so they won't freeze.

    its hard to believe, but in our state, they acutally have new homew run with cpvc plastic pipe run through the attic.... covered only with a layer of pink insulation..
    the stuff shatters very easily in low temps..



    RX...you really dont know what is rigged up under your concrete floors
    and how long before another leak springs to life.....
    .

    all you need is to install wirsbo pex and insualte it with armaflex in the attic,
    the wirsbo pex will not break, it can freeze but it wont break....

    get it all as close to the ceiling for heat under the insualtioin
    as possible, then cover it all up with an extra layer of insulation...


    I have run 3/4 wirsbo pex across ice cold attics before...,
    we did the aramflex and we covered it all with extra insulation,

    and we did install a heat cable to the pipes for extra precaution....

    its been about 6 years now

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