Anyone know what this is?

[Dave Rose]

Saw something today I've never seen. Need help.

House was early '60s vintage. It was in basement in the furnace room.

The "fitting" is hooked into both the furnace flue and water heater flue. The PVC pipe then heads two directions. One end goes through the concrete slab near an abandoned well pipe. The other end goes through the foundation wall. On the other side of that wall is a crawlspace, but the pipe enters underground so I can't see it.

One clue...in the crawlspace there is a "grid" of 2" perforated PVC all hooked together with a vapor barrier over the top. I'm licensed to do radon mitigation installs...and that's similar to how we do them...but it's odd because I don't see a fan anywhere. We ran a radon test and radon level was 1.1 pC/L...fairly low for a basement house around here.

Any ideas on what this might be? If it is some sort of radon system, a link would be helpful.

Also, just to clarify...it's hard to see but behind the "tee" of the flue, the large flue pipe goes into a lined chimney.

As a side note, there is a transformer plugged in that leads to the small black piece on the fitting...but I have no idea what it does.

I asked the current homeowner and she had no idea...they've lived there 4 years and it was there when they moved in.

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[Jim Robinson]

I think you are on the right track. I think they are using the flue exhaust to create vacuum in the radon system. No idea if that is allowed or not. I doubt that the PVC is allowed to be connected to the exhaust vent system. Kind of in between a passive and active radon system. We have very few radon systems here.

[Dave Rose]

Anyone else have any input?

[Dom D'Agostino]

Anyone else have any input?

Frankly, I don't know what it is or supposed to be, but without a listed data sheet or similar, I'd call it out. Who knows what that thing does to the draft or flue system, or if it's even installed correctly.

Dom.

[Jerry Peck]

My first thought, which was confirmed before I even posted, was that it was some type of radon mitigation system.

The house our daughter is trying to buy in Asheville has a slightly high radon level, and the radon mitigation contractor said that about the only way to reasonably install a radon mitigation in those older houses (1972, he said NC didn't even start using codes until the late 1980s - so there will not be any gravel under the slab) is to put the drill a hole next to the main building sewer which runs down through the slab and install the radon mitigation suction there - the soil typically settles some around the sewer pipe and allows a space for the radon to seep up out of the soil into and then be sucked out.

I noticed that was installed through the slab at the point as what appears to be a capped and abandoned gas line, which would have the same soil settlement as the sewer pipe, and allow the radon to be sucked out through that pipe ... expect that there is no suction fan on that pipe, just upward gravity or what negative pressure which may be created by that gravity vent.

Not that I am saying it is done correctly, and anywhere near correctly, just that radon was my first thought too.

[Dave Rose]

Thanks to you both.

I did call it out...I used wording stating that it needs further investigation and suggested several ideas such as talking to an HVAC contractor, asking the seller to connect them with the previous homeowner, as they may know what it is. Then I suggested once they figure out what it is, they should react accordingly. I also stated that PVC pipe should not be connected to HVAC flues. I looked for 10 minutes for a part number or some other info but found nothing. I even told the buyer he could take the flange apart and see what's inside, maybe that would be a clue. I also suggested they trace the PVC in the crawlspace underground (might require digging down about 1') to see if it does indeed connect to that pipe coming through the foundation wall.

Jerry, that pipe coming out of the ground is a capped well pipe. But your input is helpful thanks.

[Jerry Peck]

That flange setup looks like two floor flanges (used for mounting toilets to the floor, and connecting to the sewer piping) attached together to serve as a union.

The well pipe would likely have some soil settlement under the slab, but much more limited than what might be around a horizontal pipe - unless that well pipe went horizontal to a well instead of straight down.