Pipes under slab

[Jim S]

Hey group,

So I am in the middle of my bath remodel and am having a case of 'while I'm at its'. So here is the thing. This part of the house (where the bath is) is on a slab and the water supply pipes come under this slab and up in the middle and go on up to the other two baths upstairs. So all of the pipes are in this area where I am working. I just finished redoing the drains to accommodate what we are moving around and now I am looking at the supply lines. So my questions is about the supply lines running under the slab and up through the concrete. There are six 1/2" (three pairs) of copper lines running in the sand under the slab and I have uncovered parts of them doing the drains. My question is, should I replace them while I am in here and everything is busted up? The house was built in 65 so pipes are about 54 years old and look fine. But they do run unprotected through the sand and up through the concrete in direct contact with the concrete. We live in NE Ohio if that makes any difference and these are near the center of the house so not by an outside wall. I know this would be a difficult job but I guess would it be foolish to NOT replace these? We are on well water and our water is pretty good, only need a little softening and a filter. The lines enter the ground from a wall in the basement where there is a manifold. So there is about 10 feet where the pipes are under the slab. I have read some things about copper pipes in contact with concrete and that that is not good. I am attaching a couple pictures of this area. I'm not even sure how I would go about doing this except to drill some holes in the concrete block wall and then bust up the floor and lay new lines. This is a well built house and I want to do things right and I think we will live here for a while. Anyways hope this isn't too long! thanks

 

[Jim S]

Oh and one other thing that I thought might factor in is that it takes a long time (couple minutes) for the water to get warm in the shower on the second floor, probably because the pipes run through the ground, which may be cold. So this might be an opportunity to fix that. I just want to make sure that I'm not doing something that should be done now when stuff is all open. Like I said, I'm redoing this bath and will not want to break it up later. thanks

 

[Sponsor]

 

[Jim S]

nobody?

 

[Bcarlson78248]

In a previous home we built they ran all the supply pipes under the house, and they were all sleeved with heavy plastic down through the slab, through the ground and up again through the slab. None of the copper pipe was in contact with cement or sand. I was told this was best practice at the time, and it did work well (house was built in '96).

Since this appears to be a significant remodel, is there any possibility of running the supply pipes up and then over through the floor joists? If you use PEX, and the joists are exposed, its a fairly quick job to drill holes and route the supply pipes. You could even upsize the supply pipe size (e.g., 1/2" up to 3/4") and just run one larger pair of hot/cold pipes from the source to a PEX manifold, and then supply individual fixtures from there. The manifold would give you the ability to shut off the supply to each fixture individually, which can be really convenient.

I'm at the point where I never want to run anything under the slab unless there is absolutely no other choice. Its always a mess to fix, and nobody ever knows exactly where it runs.

Bruce

 

[Jim S]

Thanks for your reply. This would not be easy, but it could be done. Not sure how I would route them but I'm sure it is possible.

My real question is DOES THIS NEED TO BE DONE? Are my pipes on borrowed time? Like I said I have read where copper in contact with concrete is a no-no and will eventually fail. BUT - these pipes look fine. ugh haha. I'm not trying to convince myself to do it but I just don't want to pass up something that should have been done. The pipes all look in good condition and they run through sand, not dirt and the sand is mostly dry as well. Probably should just let them be.

 

[Dj2]

No, you don't have to re-pipe if you have no leaks, for now. Then again, you said that the pipes are old.

Is the house a one story? You can bring in new pipes thru the attic and down the walls. Copper of PEX, your choice.

 

[Jadnashua]

My preference would be to not have the pipes under ground where I had to break concrete to fix a leak. WEll, if you have a leak, most people abandon that line and run it through the walls or above the ceiling. The soil chemistry will somewhat dictate how long the pipes last...could be nearly forever, and in some places, you might not get 20-years! SOme of that will depends on the type of pipe, for example, K should last a lot longer than M, which is thinner. Not sure, but there is probably one required when running underground. K is a lot more expensive than M...

If you do nothing else, I'd want to insulate at least the hot lines before I backfilled and then fixed the slab. wouldn't hurt to do the cold lines as well, partly for protection.

You might also consider adding a hot water recirculation line. You don't have to hook it up, but it would be there if you decided you wanted it later. Retrofit recirculation systems work, but a dedicated return line is nicer, but harder to do after things are closed up!

 

[Jim S]

For some follow up on this, I met with the county inspector today and asked him about these pipes and he said if it were him, he would go ahead and replace them since they are mostly all exposed now anyways. So I think that is what I will do. He was actually very helpful but I did have to get a permit - oh well. He suggested running two 3/4" PEX pipes under the slab and them install a small manifold in the wall in this room to feed the upstairs baths and this one. Not sure exactly how I will do it yet. I am also thinking of ways to shield the PEX pipe as it goes thru the sand (under the slab) - possibly might use flex conduit, seems like it would work well. The under slab runs will only be about ~8 feet.