Hot Topics: Radon Abatement Works How?
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Radon detection and abatement have become more and more of an issue over recent years. If you have a system installed, the installer should be able to explain it to you. But what if you move into a home that already has one? How do you know it’s working, and just how does it work anyway? The Forum can tell you.
Original Post: Radon abatement--why does it work?
Recently got the nickel tour of a friend's new house and one of the many strange systems was a radon abatement system that used a fan to pull air from the (sealed) sump pit and pipe it outside. I assume this is intended to draw air from the drain tiles that circle the footings. My question is if radon exists in ALL the dirt surrounding the home, doses sucking the drain tiles make that much of a dent in the total? The footings are a small percentage of the total exterior surface area.
AND--doesn't the air movement and vacuum empty the floor drain traps quickly--potentially leading to even worse gasses inside the home?
I've heard about these systems but now that I've laid eyes on one all it did was raise lots of questions.
Highlights from the Thread
A new install will also include an air permeable layer of gravel under that slab, so it will be ventilating the entire underneath surface of the soil. Once they seal all of the slab to foundation walls and any cracks, the system creates a vacuum or negative pressure below the slab to prevent all small leaks that form or were missed from allowing radon contaminated air from entering the basement.
There really shouldn't be any traps draining into the perimeter system. If the perimeter system drains to daylight it might need an outlet trap that would indeed need to be kept filled, but that would not contain nasty gasses. There is a u-tube manometer somewhere down there that indicates the level of negative pressure. If for some reason that changes, then a determination should be made as to why.
In locations where the level of Radon has not been determined they will often rough in the system so that just the fan would need to be installed if later testing is high.
They aren't the original owners so the house is several years old. I believe the sub was built about 10 years ago. The radon system was installed before they moved in, along with other pricey air purifying changes to the furnace (electronic air cleaner, enormous pleated filter, UV light gizmo in the return).
I see ads all the time for radon abatement for older homes. How effective are they or are there scammers to watch out for?
Always scammers to watch out for. Two things to look for - have the radon level tested, kits available for home owners, and check for the u-tube manometer in the basement to see if it is pulling a negative pressure under the floor.
If radon levels are very low, they can test again with the radon fan off. If that is also low then the system may not need to be run. It should still be tested seasonally to be sure the reading stays low.
If the manometer is not showing a pressure difference then there is a problem with the system. Either a leak or the fan isn't working.
I hate it when systems like this are installed and information was either never provided or was lost.
“There really shouldn't be any traps draining into the perimeter system. If the perimeter system drains to daylight it might need an outlet trap that would indeed need to be kept filled, but that would not contain nasty gasses.”
My house (mid-70's) has the basement floor drains connected to the drain tiles and all dumps into the sump pit--which then discharges way out in the yard. I thought that was the norm for homes with a sump pit and not on city sewers. IF the floor drains are connected to the septic how does the water get lifted up to that level?
Guy, your initial post said "AND--doesn't the air movement and vacuum empty the floor drain traps quickly--potentially leading to even worse gasses inside the home?" I associate traps and bad gasses with a sewer or septic system which a basement floor drain should never be connected to.
You are correct that floor drains are often connected to the perimeter drain system, but traps would be almost useless without a reliable flow of water. If a basement with a floor drain has a radon system installed that path would be sealed. If emergency pumping is desired on the inside of the house then that pit or a new one would need to be able to collect any interior water and pump it out without providing an air path. I think the pump would block any air flow when not activated.
So in the ideal install there is near-zero air flow from the conditioned space to the outside? Floor drains are plugged, penetrations and porosity sealed. All the air is coming from the soil. Can you pull much air out of soil 6-7 feet below grade? For a manometer to be employed this fan must be a very low static pressure type. Is it typically moving a lot of CFM or just a whisper?
The purpose of the fan is to create the pressure difference because we can never (almost) get a perfect seal between the basement (conditioned or not) and the sub-slab. I would expect a whisper and if it was a lot more I would go looking for leaks, especially in winter with frozen ground and a snow pack. It could also be drawing from the drain system so perhaps more air. I would have to search to find the recommended pressure indication, but should be easy to find.
I visited one home where he didn't want a second sump so I suggested he create a sealed weighted rigid foam cover or maybe a soccer size ball resting in a rubber gasket. The idea was, if a pipe broke the rising water would float the lid and allow the sump pit to go to work. Never had the opportunity to make a follow up visit, but judging from other work he had done I suspect he created something.