My radon mitigation project was not a DIY story, but it could have been. Whether you choose a professional installer or do-it-yourself, perhaps my story will set you at ease.
I live in a 107-year old farmhouse in Ohio. It is set on a glacial plain at the base of limestone hills. Most this area was swamp before the area was drained.
In my county radon can be a bad problem. We know someone who had a family member die of lung cancer. They blamed radon as the culprit, so my wife decided we needed to test for radon.
When you test for radon you are actually testing for radiation. Radon gas does not harm people by reacting chemically with their bodies. Instead it emits radiation that damages their cells, some of which might become cancerous.
From the health department we were able to obtain some test kits. There were instructions about where to place the kits and we had to leave them in place for a few days. This was a short-term test kit. We sent the kits in to a lab for analysis. While the kits were free I think we might have paid for the analysis. The kits came back above what is considered safe levels.
We tested a second time with a long-term test kit and this time the concentration was higher. Our highest reading was around 18 pCi/L. A safe level is 4 or below.
The concentration was highest in the basement. This is normal. Radon gas comes from the ground, so it is seeping into your house from the basement walls and floor.
If you live in an old drafty house, the natural turnover of air may keep your levels down to a decent level. We have a semi-drafty house, but it was not enough to solve the problem.
I needed to engage in some radon removal if I was going to be able to safely use my basement.
Radon isn’t super-toxic. It is dangerous over time, with lots of exposure. I could have elected to stay out of the basement and avoided heavy exposure, but we have our laundry room downstairs, and a wood furnace, and a small room which has at times served as both a library and a spare bedroom. I decided radon mitigation made more sense than losing the use of my basement. Besides, some of that radon made its way upstairs so that even the first floor had radon levels above what was considered safe.
I began to learn about radon gas, the symptoms of radon poisoning and radon reduction. One of the things I read was that radon can also contaminate water. Since I use groundwater I figured the water might be part of the problem.
Radon is still a gas in the groundwater, but it is dissolved. However, as you pour the water from your tap some of it will bubble out of the water and into the air.
I decided to get my water checked out. I ordered a kit online, which simply was a couple of vials for sample collection and a box with which to mail them in to a lab. As I recall the fee was $75.00.
Radon in the water is also a source of radon in the air. It can result in extremely high radon levels in places like bathrooms with showers. The radon escapes from the shower water into the air, making the bathroom a dangerous place.
To treat radon contaminated water you have few different options, but they all come down to recreating the shower effect. Either air is bubbled up through a stream of water or water is sprayed into air. The radon escapes into the air, which is vented outside the house.
In my case I did not have radon in my water, so I focused on radon leaking into my basement. This is the typical way that radon gets into your house. Radon forms underground. The rock below contains trace elements of uranium. The uranium decays over time, becoming radium. This is a slow process, but while its going on there is a constant, low-level radiation coming from the uranium.
There is a decay chain, whereby larger elements break down into lighter elements, emitting radiation along the way. Radon is but one link in that chain. Uranium becomes radium, which eventually becomes radon, which eventually decays into something else.
Radon itself doesn’t last long, but as a gas it is capable of moving within the rock formations. It is chemically stable, which means it isn’t going to react with the rock. Instead it passes through the rock and into the atmosphere. If it passes into an enclosed space, like a cave, or a basement, it can develop high concentrations. You can’t taste it, or smell it, since it doesn’t react chemically, but it emits radiation, and if that radon is in your lungs, some of that radiation will irradiate you.
It is all happening on a very small scale. It doesn’t fry your lungs. It just fries a few cells. Most will simply die, but some may mutate in a dangerous way and become cancerous.
Since the radon gas is coming through your basement floor and into your home radon mitigation involves preventing the gas from getting past your floor. There are two basic ways to do this, and often both are used.
First, you can seal the basement floor. In new construction there is often a plastic sheeting underneath the gravel. This will stop a lot of the gas. However it will also serve as a collection point for the gas, and some may eventually leak in through seams in the plastic. Usually this is accompanied by a drain path for the gas. The idea is similar to a French drain. Gravel is used to form a channel under the plastic. The gas flows to a pipe which takes it out from beneath the basement floor and vents it to the atmosphere.
This second means of mitigating, venting the gas that is trapped under your basement floor, is the workhorse of radon reduction, but usually it requires the addition of a radon fan or radon pump. This creates a lower pressure underneath the basement floor. This means you reverse the leakage. Instead of radon gas leaking into the basement, basement air seeps into the space below the floor. This keeps the radon out.
A radon pump is simply a blower that is inline with a vent pipe. They are designed to work outside of the house, so they are insulated from the elements. They are designed to be quiet, so they are well insulated. They are designed to operate continuously for many years, so they are especially robust.
The problem is that you have to take this vent pipe and insert it beneath your basement floor. The way this is usually done is to drill a hole in your basement floor. Since there is dirt or gravel or something underneath the concrete you dig out a sump hole. This is just a bigger hole directly beneath the hole in your basement floor.
If you are lucky there is a thick layer of gravel beneath the concrete. Air will flow easily between the gravel so it is easy for the pump to suck out the air. Soil, whether clay, or loam or sand, isn’t nearly as good. The air can still flow to the pump but it requires a stronger pump and your radon reduction may not be as effective. You may even need to add more sumps and more pumps to pull the radon out from underneath the house.
Even where conditions are ideal you may need several sumps. Some houses have internal supporting foundations that go down much lower than the floor. You may need a sump on either side of the foundation, which will add to the complexity of the plumbing required to connect the sumps to the pump or pumps.
Although I considered doing the job myself I had too many questions. I was not sure where I needed to build a sump or if I would need more than one. I was not quite sure of the size of the pipes and the pump that I would need. I could handle all the plumbing and wiring, but I was afraid that I would make some rookie mistake and end up with a system that failed to solve the problem, or which would fail with bad weather.
I opted to have a radon professional install my system. Having seen the work involved I am not unhappy with my choice, but now I have the confidence that I could do the job myself if I had to do it in a later home.
The one thing that my pro pointed out, that I would not have considered, was the need for a separate sump for the kitchen basement. It is an addition to the original house and has a separate floor.
He charged me $1100, which seems to be about what others are charging across the country. I hear of people paying between $1000 to $1500 for a radon mitigation system.
Together we identified where he was going to dig the sumps and where the sump was going to run up the outside of the house.
He had the bright idea of venting over the kitchen roof, which is only one story high. This made the installation easier, but also made the vent stack less obtrusive.
Locating a vent is complicated by the need to keep the vent pipe at least 10 feet from any window that can be opened. You don’t want the radon to end up coming back into the house.
This is not just a good idea, it is part of the code governing vent pipes and radon mitigation.
Unfortunately vent pipes look rather ugly. Bathroom vents run up between walls until they reach the roof, so they are mostly hidden. If you were building new you could keep a radon pipe inside, but it is not usually practical for a retrofit, and the need for a pump means it is better to have it outside, to reduce the noise. While a radon pump is quiet, it runs continuously, and you would not want a constant hum inside your house.
We decided to make the sumps along the same wall that we would vent through. This kept the design simple. He put one sump in the room beneath the kitchen, and he put a second sump right behind the dryer, in the laundry room.
Creating the sumps was fairly easy, with the right equipment. He drilled about a dozen ⅛” holes in a circle, then took a small electric jack hammer to pound out the concrete. Once he had removed the concrete hole he took an iron bar and started pounding the dirt underneath the hole. With a garden hand trowel he removed the dirt, then pounded some more loose. He dug down about 18” (about as far as he could reach) but widened the sump so that it was wider than the hole in the concrete. This was the most difficult part of the job.
In some systems a sump pump will be needed. It depends on your drainage and groundwater situation. If water gets under the house it can fill up the sump and prevent the radon pump from doing its job. In my case I did not need a pump.
A 3 inch pipe was used to vent the sump. It was set into the hole and fixed in place with caulking. The contractor used a silicon-based caulk. Silicon tends to maintain its elasticity longer. If the caulk became hard and cracked you would end up drawing basement air into the pump, reducing the amount of radon you were evacuating. Eventually it might fail to draw any and you would have high levels of radon again.
If this caulking fails you will probably hear a hissing or whistling sound. That, anywhere along the vent pipe before the pump, is a sign of a leak. As part of your maintenance of the system it is a good idea to walk the length of the pipe and listen. Fixing such a leak is easy, but only if you find the leak.
Some radon mitigation systems use a 4” pipe, and a 4” pump that mates to it. The advantage of the larger system is that it can draw out more air and with less resistance. The pump will last longer because it is not working as hard. The disadvantage is the additional cost of the larger pipe, the larger hole, and the larger pump. If I had a larger house, with a bigger footprint, a 4” pipe would have been better. If I were doing this as a DIY project I would have gone with the 4” system with the philosophy that there is less of a downside to going large than there is to having a system that is too small.
My house now has radon levels averaging around 1 pCi/L. I have regained the use of my basement and my wife is happy. The radon pump runs continuously but I can barely hear it, even when only a few feet away, and not at all from inside the house.
There was a slight issue with the piping. It vents out of the basement through a hole near the ceiling of the room below the kitchen. It then has to travel across the room and go underneath some stairs, which forces it to drop down at an incline that carries it across the top of a window. As I have plans to make this room nice it create a bit of a design problem, but no worse than the plumbing and the wiring that run along the ceiling in that room.
In conclusion, it was a successful radon mitigation project. It was far less costly and intrusive than adding a bathroom, or renovating a kitchen, but there is less to show for it. Unless you consider not getting cancer a benefit. In which case there really was a benefit to my little radon mitigation project.
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