Sealing HVAC lineset inside PVC sleeve
Earlier this year, we installed two 5-ton heat pumps with linesets run underground, sleeved inside 4″ corrugated PVC pipe. After recent landscaping (including pouring a slab), one of the sleeves (left one in the picture) appears to have been punctured. Now, water enters the sleeve during rain and leaks into the basement. The penetration itself is sealed ok (about 2′ sub-grade depth). The only issue is really water inside the sleeve.
I tried last week sealing the PVC around the HVAC linesets using GreatStuff closed-cell spray foam, but it didn’t hold up. The issue seems to be water getting between the copper and the HVAC insulation, causing a slow drip – although the entire 4″ was filled with the spray foam.
I’m considering removing a small piece of 3–4 inches length of the HVAC insulation around the lineset and reapplying spray foam directly to seal around the copper. However, I’m open to other suggestions.
The ideal solution—cutting the slab, excavating, and installing a new sleeve—is cost-prohibitive and not practical during winter. Any advice on how to address this without disrupting the heating system would be greatly appreciated!
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Replies
This is why I prefer to have these lines enter above grade :-)
I don't see a problem with you cutting out a section of the pipe wrap and then using canned foam around the rest of the lineset. You'll want to maintain spacing between all the different things in the pipe so that the foam can expand and seal around ALL the things in the pipe. Just rig something up to hold the two pipes in the line set and the electrical wires all spaced a little apart from each other and from the walls of the underground pipe and you'll be fine.
I'd try Loctite's TiteFoam for this (which apparently is now branded as "GE", but Henkel still makes it), since it's denser than great stuff and will probably hold up better in your particular application. Great stuff is lower density and not as durable -- I think you need the extra durability here. The tradeoff is the TiteFoam product is more expensive, but one can of their "Big Gap Filler" is probably enough for both of those pipes, so you should be fine.
A possible solution for later is to dig out around those pipes later, cut a hole in the bottom at a low spot, then dig a hole underneath and fill with washed stone to create a sort of drywall to drain the line. It's not ideal, but it's better than water coming into your basement. The downside is that this can only handle limited amounts of runoff. You'll want to try to seal the exterior to keep water out of the pipe. You can use the roof sealant the way they seal pitch pockets on roofs. You may also be able to run a thinwall PE pipe through the corrugated pipe as a sort of sleeve/liner to provide a waterproof pipe to enclose the linesets, but you'd still need to seal around that, and it would probably be VERY tricky to pull it in if the corrugated pipe has any bends in it.
Bill