[Bobby Ratliff]

Hi, I live in central Texas and want to plumb under a cement slab. I am not comfortable using Pex piping. I wanted to use copper. My question is should both hot and cold water lines be insulated or just hot and what would be best insulation. Thanks, Bobby

[Flying Blue Eagle]

BObby RAtliff - #1 you do not want the concrete slab to come in contact togreather, they don't mix very well. There is a chemical reaction that sets up and eats the copper , #2
I would bury the copper under the slab enough to where the concrete won't bother it , I used to take 3" pvc and run the 1/2" or 3/4" cpvc pipe in threw it to the water heater and go from there;if and when you develop a leak it is easy to get to and repair it . If you do it this way ,when you come to the hot water tank area,use about 3 or 4 ( 1/4 turns) to come up inside the house, later you will see why . Easier to bring cpvc in and not break it . Cpvc and pvc bend easy, do not run your hot water threw the pvc COLOR WHITE,
AND CPVC IS yELLOWESH COLOR if the pipe comeing from the meter is under ground ( BELOW FROST LINE > CAN GET THIS FROM THE WATER DEPT> OR BUILDING PERMIT OFFICE OR ANY PLUMBING Business Ive never had to use any insulation staying under frost line , inside the house you can use sticks or thick rubber insulation , its formed round and comes in several different sizes, Lowe's AND HOME DEPOT AND MOST BUILDING SUPPLY PLACES HAVE IT .
Easy to work wity and you will need some gray duct tape to wrap the joints and angles . GOOD LUCK AND GOD BLESS ;; F.B.E.

[speedball1]

Hi Bobby,
Here in Florida we run our copper under ground. If the contract calls for insulation we use Armoflex ,(see image) on the hot water lines. FBL was bang on when he said,

you do not want the concrete slab to come in contact togreather, they don't mix very well. There is a chemical reaction that sets up and eats the copper

so when we bring the copper up out of the slab we always insulate the line with a piece of Armoflex so no part of the copper comes in contact with the cement pour. Good luck, Tom

[Milo Dolezal]

Yes, you can run type "L" or type "K" copper under slab. No sweat joints below slab. If sweat joint is unavoidable, sweat using silver. Buy "soft" copper. It comes in 60' sections. You run it in "loops" from wall to wall, connecting to other fixtures via manifolds. Use plastic sleeve where pipe penetrates concrete to separate concrete from pipe. Yes, you can insulate pipe with foam insulation if you wish.

In my region, copper under slab is not allowed any more. Except where there is no way to run the pipe, small section will be allowed covered with concrete. Just like anything else, copper will eventually leak. Repairs are expensive so are repipes.

[speedball1]

In my region, copper under slab is not allowed any more.

Another wackey code by UPC. Just one more in a long line! Wonder what they'll outlaw next.

[Milo Dolezal]

Tom, it is all about Trial and Error. If something proves over and over that it is not working and causing problems in the long run - the application procedures will change. It certainly proved its negative sides here and that's why it is not allowed to place copper under slab in So. California any longer.

[speedball1]

Milo, Does that mean that you have to pipe overhead? We don't do that around here unless we have a repipe job. The reason being that if a leak develops under the slab all you have to do is locate and repair it but if a leak develops overhead you have your ceiling to repair, the rug to dry out and any furniture that's soaked refinished. Yeah! That makes about as much sense as the rest of your restrictive codes. You guys just got to get up every morning wondering, " Gee! I wonder what their gonna outlaw today?" Must be a chore keeping your code book up to date. In my opinion the UPC places more work on the plumber and more expense on the homeowner. Everybody loses under UPC! Just my two cents! Tom

[Milo Dolezal]

Yes, Code is complicated, sometimes makes no sense at all and changes happen very often. Sometimes the only way to find out is during Inspection when you are asked to re-do something that was up to Code last week - and is no longer up to Code requirements today.

Yes, pipes are run overhead. Slab leaks are very expensive to locate and repair. Of course, it is not the plumbing that is expensive - but everything else around it. The Code has changed about 10 years ago or so.

[speedball1]

Yes, pipes are run overhead. Slab leaks are very expensive to locate and repair.

Not as expensive as replacing, 1) the carpet, 2) the dry wall that sucked up the water off the carpet by capillary action or 3) the furniture that was ruined by a water pipe that let loose in the middle of the night and flooded anything under it.
Like I said, Milo, You work under a restrictive code that makes more work for the plumber and more expense for the home owner and the really odd thing is I've never had a decent explanation from either Growler or you as to why these codes were written. For instance, why must washer traps be 6" inches over the floor line and since we get so many stand pipe backup comnplaints why is the stand pipe held at 30 inches when they should be 36 inches Minimum? Some of your amendments just don't make any sense at all. You guys just got to be wondering what's coming next! Have a good one, Tom

[jlisenbe]

I get a real kick out of reading these exchanges. I learn a lot from you guys, even in areas where you don't completely agree.

[speedball1]

Jlisenbe,
That's what makes this page so interesting and fun. If everybody agreed we would spend all our time congratulating and slapping each other on the back. Each expert has his own opinion about what he thinks should be done. This gives the Asker options and that's what makes this the best plumbing Q & A page on the web. So let's keep on disagreeing without fighting about it. The more opinions we have the better we can serve the askers. Correct? Cheers Tom.