Can PVC be encased horizontally in concrete

[tpcolson]

Have an unfortunate "this is the only way this is going to work" situation with a DMV repair, resulting in the repair portion of the drain pipe, having to run 4 feet horizontally (yes, at the correct slope of 1/4"/ft) before turning up into the main vent stack...mostly above the gravel sub-grade and tapering into being completely within the 6" horizontal space where the concrete slab will be repoured. Question is, can 3" sch. 40 PVC pipe be directly embedded in concrete? Not covered by, or under, but directly embedded (concrete will fully encase 4ft of the pipe). Wondering if the heat of curing will warp/crush the pipe? I know horizontal stub-outs come through a concrete slab all of the time with no issue, but not seeing a lot of examples of horizontal embedding. I'm sure there are other ways to do this without the last-ditch option of embedding PVC horizontally in concrete, but those involve a 5-figure $$ removal of the entire basement slab and replacement of every single pipe.....just to get that 4' run of PVC encased completely in the gravel sub grade. The attached photo is a very poor rendition of what's going on here, not to scale, best a non-computer person could do!

 

[Jadnashua]

PVC expands and contracts quite a bit with temperature changes, so bonding it into a rigid jacket might be a problem, especially at a joint. It should work if you could sleeve it. One of the pros needs to confirm.

 

[Sponsor]

 

[tpcolson]

I guess to add clarity to my question, would the heat of the curing concrete deform the pvc? I have a couple of options for protecting the joints, especially with pipe thermal expansion, but I'm more concerned about the curing temperature of the concrete. Sleeving it.....would be hard...if not impossible...given the lack of space in which to get a sleeve around some of the pipe.

 

[Reach4]

I don't think heat will be a problem. The concrete is not that thick. However there can be other considerations. Take a look at these:

https://terrylove.com/forums/index.php?threads/wrapping-pvc-for-concrete-pour.26134/
https://terrylove.com/forums/index.php?threads/sleeving-pvc-for-concrete-pour.41119/
https://terrylove.com/forums/index.php?threads/pvc-pipe-in-concrete.22467/
https://terrylove.com/forums/index.php?threads/dwv-fittings-allowed-in-concrete.31873/

 

[CountryBumkin]

According to this source http://cement.org/tech/pdfs/pl972.pdf the "worse case" temp rise is a concrete temp rise of 100 degrees during hydration, but that is still below the max temp PVC can withstand (so if the concrete was 100* when poured (which it won't be) and it rose another 100* (which it won't), its still with in the temp range that PVC can tolerate).

 

[CountryBumkin]

Oops - double post

 

[tpcolson]

Yeah...those other posts echo what I'm dealing with: "Not the ideal situation but it's what I have to work with". I'm not going to jack the house up or start tunneling through the foundation footing just to get a vent stack in. This is the best, cost-effective repair I could implement in an otherwise impossible situation (the house was originally plumbed with NO vent!). But that link you posted with the paper about temperatures and types of cement was helpful. I guess I need to choose the right cement (Type IV I'm guessing) and make damned sure I use the right amount of water per bag, use a drum mixer, and make damned sure it cures properly. I know I know, not supposed to have a pipe 2" below the surface, it's gonna crack, end of the world..... I can deal with that, rebarred the s*** out of the repair hole. If it does crack, and it's an issue, can also retrofit concrete staples.

 

[Reach4]

But that link you posted with the paper about temperatures and types of cement was helpful. I guess I need to choose the right cement (Type IV I'm guessing) and make damned sure I use the right amount of water per bag, use a drum mixer, and make damned sure it cures properly.

Note figure 1 has lines for 12 inch thick concrete through 40 inch thick concrete. If you keep your concrete thinner than 12 inches (300 mm), I don't think you will need to worry about a temperature rise regardless of which of the mixes you use.

 

[Craigpump]

I've seen 4" sch 40 installed in a 6" well deform when the cement began to set up.

 

[CountryBumkin]

Note figure 1 has lines for 12 inch thick concrete through 40 inch thick concrete. .

Yeah, that 100* rise is for 40" thick concrete. You won't see that in your slab.

 

[Cacher_Chick]

I would be more concerned about the movement of the pipe during normal expansion and contraction in use. The commercial installs here always use cast-iron pipe below grade of a structure, which would seem to be a better solution in a situation such as yours.

 

[Master Plumber Mark]

I dont know where you guys are located but in Indiana they have been installing sch 40 pvc in both commercial
and residential slab homes
for about 50+ years now directly in the concrete and pea gravel without any real issues to speak of...
I have done many slab homes in sch40 pvc...

dont worry about it...

if you are really worried about the flex in the pipe or concrete , then why not wrap the pipe in cardboard
and use duct tape to hold it together for the pour???..

the only thing I worry about in concrete is the water lines and I always protect them with
aramaflex rubber coating....HOT WATER LINES MOVE