Thread: Electrical PVC conduit used as drain pipe

I 'know' it's wrong, but can't find an obvious answer why not. 1983 house with mixture of ABS and white PVC, and quite a bit of gray schedule 40 PVC electrical condiut for waste line plumbing. Stamp on the gray PVC says [1-1/2" CARLON PVC CONDUIT, "PV DUIT 40 PLUS", NEMA TC2]. This is obviously electrical PVC conduit. Since there is no ASTM stamping, it is obviously not intended for plumbing. My stupid question of the day is why is this Schedule 40 PVC not suitable for waste line plumbing? Is there some sort of chemical reaction? Is it because the solvents for white plumbing PVC don't bond with electrical PVC?

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The 2006 IRC code and commentary Table P3002.1 (1) gives the ASTM standards listing for PVC DWV pipe. I would say if it is not listed here it is wrong. Also P3003.2 number five prohibits solvent cemented joints between different types of plastic pipe.

Electrical conduits and their fittings, even PVC conduits with solvent welded fittings *are not* tested for water tightness, and, in fact, *are assumed to leak* when installed for electrical use (where no water is in them). That is why electrical conduits placed underground must have conductors rated for direct burial, because we 'know' the conductors will be in water, if there is any water around.

Now, assuming that water is in them (the use you described would do that ) ... what would make them 'not leak' or 'not be assumed to leak'?

I ran across a similar situation yesterday. This time though, the conduit was used for the primary condensation drain pipe for the a/c in the attic. That's right I said primary! Water constantly drips from the conduit at the soffit when the a/c is running.

It had PVC to the soffit area then liquid tight conduit for the down turn at the soffit. See photo. Yes, I called it out as an issue.

The unit had no secondary drain pipe either and the drain opening in the auxiliary pan was open with no secondary drain pipe attached.

5 year old house in rural area, no code enforcement when the house was built.

Eric

Eric,

Many don't think that the water leaking from a condensate line continously against the foundation is an issue. I disagree.

Over the years, I've heard several SE's say that the movement that has occured in a particular home was caused from the condensate leaking next to the foundation. Seems a constant drip can cause the soil to swell up in that area and cause some upheaval issues when the rest of the soil around the foundation has been allowed to remain dry.

The first time I ever heard it was at the first home I ever owned and was having foundation issues. SE told me this personally, and I've heard from others since then.

rick

I have found in many counties (parishes) and cities in south Ms. and Louisiana, the overflow for the hvac must have a p-trap and be piped into the main dwv system. You might want to check the local code on this.

There is no issue with the material from a practical viewpoint. I was the Quality Assurance Manager in a plant that extruded PVC pipe for several years. The formulation for conduit was the same as for water pipe except for the addition of the colorant (primarily carbon black for gray) and the printing.

However, the production testing requirements and the qualification testing requirements differed between the intended applications. The tests proved that both would hold water, but the pipe intended for water distribution underwent various pressure tests. The conduit was not tested under pressure.

Darrel Hood
DILIGENT PROPERTY SERVICES