Radon mitigation system does not look right

The house had a radon mitigation system installed by a certified individual. In the middle of the discharge pipe there was a “Y” installed that was open. It initially had a piece of tape, maybe more, but that was coming off. To me this does not seem correct, as it could just be dumping the radon back into the house.
The system also had 5 sub slab suction ports in the wide open basement (about 2,00 sq ft). I have tried to reach out to the installer with no such luck.


For some reason does not look like this photo uploaded with the post. Here is the “Y” in question

Is this a passive system (non-powered)?

Yeah it’s definitely not correct to be open. Maybe they were going to add another riser but didn’t and never capped the pipe. If it is an active system (has fan), that opening is hampering the ability to withdraw air from the soil.

On another note, I have never seen valves installed in the system like that. Looks like they put them on all the risers? I would assume the idea is to be able to fine tune and balance the system.

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Yeah didn’t seem correct. I have also never seen valves nor 5 suction ports.
Thanks for the response.


Adam, were you able to confirm that the PVC pipes penetrated the floor? The closest riser looks like it is just caulked the concrete. So many things wrong with that set up.

As @ruecker pointed out,

It shouldn’t have valves either. The whole system appears to be an overly elaborate scam of an install.

Were you able to see any vacuum gauges installed in any of the system? Something like this:

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I had to research the valve thing this morning since I have never seen them used in my area. But then again I haven’t seen a system with 5 suction points either. As it turns out, it appears they are allowed to be used to balance the system but must be labeled with “Do Not Alter” etc…

Section 6.3.6 Multiple Suction Points

Thats good to know Ryan! Im going to make a not of that should I ever come across it. Thanks.

I was told by a local mitigation installer that when multiple risers are used with only one fan, balance calculations had to be made for length of pipe, fan location, etc… similar to balancing an HVAC system. Also, if the home was not built with outlet pipes installed prior to the floor being poured, a big enough hole in the floor would have to be cut out to dig a small pit for washed gravel/rock, pipes installed, and floor replaced. It does not appear (in the OPs pictures) that this was not the case here, nor were vacuum gauges installed in any of the risers anyway, so it would be unclear just how much suction is at each riser.


Yeah, it is new info for me too. What is interesting is that I could only find reference to the balancing valves in the “existing home” installation standards. No mention is made of them in the “new construction” standards. I would be curious if they are not permitted in new construction and other means have to be used to balance the system.

I bet it’s probably because most “new construction” starts off with a single pipe only installed as a “passive” system during construction, ran up through the home’s framing, attic, and out the roof top, with a power receptacle placed near the pipe in the attic for the addition of a fan. No need to “balance” the system with only a single pipe.


Do you know where the radon (if there is one) was located? It could be on the outside of the house or in the attic. In either case, the PVC pipe should be capped.

I had the opportunity to reach out to the initial installer and ask what his thinking was. He says that the substrate was so compacted below, they had to keep coming in to add another suction port (5x). His last ditch effort was to add the open port to the basement to also draw the radon out. He claimed having the fan actively running can not allow the radon to back flow through the open port.
You guys are right that they never opened any of the holes up larger to remove aggregate. The pipes felt very loosely connected when pushed on. The fan is a small standard size fan. Sounds like a challenging install which this company was not properly prepared to do.
They did have a manometer installed on one port (furthest from the fan) which a majority of the water had evaporated or leaked out- about .5" change (liquid was below the numbers).
Interestingly the house was tested 2 years ago and showed 2.2 pCi/l-winter test.
Either which way, I also spoke with my go to mitigator and he also disagrees with the open port and the system will need to be reevaluated.

How often does one know where the source of the radon comes from?
Around here, it’s usually test and then install a single sub slab. We had one test over 136 pCi/L- largest I have ever seen. Still one suction port to get down below 2.0

Oh I just read that better- Radon Fan. That was located outside

Having the port open in the basement is not good practice at all. You are creating low pressure in the basement which just draws in more radon from the ground. It is futile.

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I’m probably misunderstanding your question but it comes from the radioactive breakdown of metals in the soil and can vary widely from house to house.

Usually one suction point gets the job done in my area. I’ve seen two but never three or more suction points in my area. Unmitigated houses around me approach 20 pCi/L in my experience.

I misread the post above asking “Do you know where the radon (if there is one) was located?”.
I have heard of radon sniffing devices, but never seen or heard of one in practice.

I meant to say Radon Fan. Once the holes have been drilled through the floor for the PVC pipe, they should have removed at least a 5 gallon area of soil though the hole. Then, replaced with some crushed stone. If there is a plastic vapor barrier below the concrete and a crush stone base beneath that, the system should create a vacuum throughout the area under the slab (floor).


That open pipe to the basement will likely reduce any suction from the slab. I think @ruecker has it right, it could actually increase radon levels.


The open pipe will be the main source of suction. Less resistance and will be the main draw. Every other buried pipe is essentially worthless. It should be capped if that system has any chance to to be effective.