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XPS around drain pipes?

Posted by nick_net (My Page) on
Sun, Sep 21, 08 at 10:00

I have a mostly buried basement in Maryland that I am finishing. I will be using 1.5" XPS (R value 7.5) on poured concrete exterior walls mounted with furring strips. Then 2x4 framed walls with unfaced fiberglass covered with drywall.

Running along some of the walls, I have a 3" drainpipe 3' from bottom and 5' from top going out to septic system mounted directly to the concrete. My question is this:
Can I install the XPS above and below the drain pipe? Would that defeat the advantages of the XPS? I can move the drain pipe out if required but that would be a real challenge.

Thanks in advance!

Follow-Up Postings:

RE: XPS around drain pipes?

Just put the XPS tight to the pipe. It's certainly not worth moving the pipe.

RE: XPS around drain pipes?

You might want to add some low expansion polyurethane foam in any gaps.

- get the LOW expansion stuff. You don't want to break the pipes when it expands
- try get the stuff that stays flexible

RE: XPS around drain pipes?

- "get the LOW expansion stuff. You don't want to break the pipes when it expands
- try get the stuff that stays flexible"

WRONG! You need not worry about high expansion foam breaking the pipe. The pipe is sched.40 PVC or ABS and it can easily withstand the pressure of either type of foam.

The plumbing code requires that when we run any pipe through a masonry wall we are required to sleeve the pipe. To make a sleeve we begin by installing a short section of pipe which is 2 nominal trade sizes larger in diameter and long enough to extend through the wall with 2-3" extending out either side. The sleeve is sealed to the wall by any suitable means, then the desired pipe is run through the sleeve and the space between the inside wall of the sleeve and the outside wall of the desired pipe is filled with expansion foam.

I always make it a point to use "High Expansion" foam in the sleeve to insure it will totally fill the cavity and push out the opposite end of the sleeve.

I would caution you that there should be a cleanout in the close proximity to where that pipe exits the structure. If you enclose that pipe you must be sure check for that cleanout and if necessary you must extend the opening of that cleanout so it can be accessed.

RE: XPS around drain pipes?

I have a similar situation. The clean out is, as you say, quite close to the pipe. The cleanout is somewhat flush with the floor except for the cap that has a big square (2") that evidently is turned to get the cap off. I do not mind carpeting around the clean out ...I do not want to cover it. Is there however another sort of cap that can go over the clean out that does not protrude up so one that keeps it closer to the floor.

RE: XPS around drain pipes?


While we seldom need to place a cleanout in a walkway area in residential plumbing, however they are common in commercial plumbing and as you point out, a conventional cleanout plug with a raised head would present a serious trip hazard. To meet the need they make a flush cleanout plug that has a long recessed slot like an over sized screwdriver slot.

You may not be able to find one in your local home supply center such as Lowes or Home Depot because even though the keep a huge inventory, they often confine their inventory to the fast turnover items.

When looking for a rare or unusual plumbing part you will generally have much better luck trying your local neighborhood hardware store, such as Ace Hardware, True Value Hardware or an independently owned hardware.

To give you a bit of a heads up on your search I pulled down my "Genova Products Company" catalog. (Genova is one of the leading manufacturers of PVC pipe)

In the catalog the item your looking for is called a:

"Toe Saver Floor Plug"

3" part number is 71853
4" part number is 71854

If your local hardware store does not stock the item ask them if they will special order you one? If not, you can contact Genova Products Co direct by snail mail:

Genova Products Inc.
9034 E.Court St
Box 309
Davison, Mi. 48423-0309

You might also run a search online to find their homepage and perhaps an email address or current 800 number.

RE: XPS around drain pipes?

Well, thank you very much.

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