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Radon Level Over 4.0


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I installed a radon system in a ranch style home and the result was over the 4.0 limit. The manometer has a reading of 1.2 It does have an uplift station for water from a sink. Could the sink short circuit the system. It also has a lower level fire place. Not sure if this could be a problem. I will be doing diagnostic on the house tomorrow. Any extra input would help.

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but if it starts at 6.7 and it does not go down much i would like to know why. it should be down at least to .5

OK, then. Is the house over a basement or a crawlspace?

What test method was used to establish the radon levels?

What, exactly, did the mitigation consist of?

What has been the elapsed time between the initial test and the most recent test?

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Before doing anything drastic, I would give the system time to ramp up to its full potential. As it continues to draw air it should slowly dry the soil under the slab which will make air draw communication across the underside of the slab improve over time.

It at least worth a wait to see what happens. I'd say a few months maybe.

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The house is over the basement. There is no crawl space. The mitigation system is the corner of the basement. The mitigation consists of a sub slab depressurization . The second test was 48 hours after the installation of the mitigation system.

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dollars to donuts that it is a single pipe stuck into a concrete slab floor.

Typically: Fireplace, as described, no effect

The lift pump should not have any effect, if properly installed.

You are asking a question without letting us know the "facts".

Got photos? etc

Is the house 35+-yrs old?

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Tom,

Did you have a home inspection? If not, there are several inspectors that frequent this board that are from that area. Likely they would be quite helpful.

Caution this is drift. I average four or five calls per week asking about radon mitigation systems improperly installed. Some are just plain crap and most are improperly installed. In this area, most are just plain wrong. The defects range from configuration to electrical to materials. Most folks will not discuss radon gas in a calm and reasonable way and that just gives the scam artists an opening. Radon and mold are the bane of the inspection business.

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What was the soil under the house when you dug the hole for the pipe? Typically the only time I see a retest fail is on older houses when the soil is clay with no gravel under the slab. If this is the case you may have to install additional suction points and use a stronger fan.

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Lemme get this straight; you had a mitigation system installed based on the results of a short term radon test and are panicking because the levels have only decreased by 1/3 in a 48 hour period right?

Are you aware the levels could vary that much over that period without a mitigation system?

My advice would be to go ahead with the purchase, assuming this is the only stumbling block, and contract a long term study after you've moved in. With data from six or eight months of monitoring your radon tech should be able to determine if the mitigation system you have is adequate, or even necessary. If you do need mitigation you will have the data to design an appropriate system.

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I do re-test all time after the mitigation system has been running for only 24-28 hours. Your system is not working if the levels only went from 6.7 to 4.0+. All the companies I know gurantee their work and if the retest fails they come back out at no additional cost and keep at it until the levels are below 4.0. I rarely find a retest with levels over 2.0, most are closer to 1.0.

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All valid points.

Folks get way to freaked about radon levels using EPA thresholds; the entire approach is set up for confusion.

Folks mistakenly imagine 4.0 is a toxicity threshold; it's not. It's a performance based threshold. Ask a radiologist, or any one involved in actual science, about performance based thresholds, and they look at you funny, wondering what in the world you are talking about.

That's an appropriate response.

Look into what the international scientific community has to say about levels, and you will find little to no agreement. Some countries say in the high teens, others vehemently say it's gotta be nothing.

Due to the teeny box the EPA has put us all in, my professional response has to be "gotta be 4.0 or less, etc., etc.". If it was my house, I'd move in and not even think about it. If I had absolutely nothing else to concern me, I'd do what Raymond says, test in all sorts of conditions, plot a graph, apply real science to the matter. Then, you'll know.

If you're working in the EPA sound bite method of analysis, you'll not know.

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The soil was sand and just a little rock.

the home was built in 1970. It is a 3 bed room ranch style home. The uplift station and all cracks are sealed.

There is one drain 4 or 5 feet from the suction point that goes into the uplift station. There is also a pipe the goes from the uplift station to an area by the furnace and water softener. It has 2 hoses coming from it. One is for the water softener and the other is just open laying on the ground. They sealed the drain and plugged the hose.

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Lemme get this straight; you had a mitigation system installed based on the results of a short term radon test and are panicking because the levels have only decreased by 1/3 in a 48 hour period right?

Are you aware the levels could vary that much over that period without a mitigation system?

My advice would be to go ahead with the purchase, assuming this is the only stumbling block, and contract a long term study after you've moved in. With data from six or eight months of monitoring your radon tech should be able to determine if the mitigation system you have is adequate, or even necessary. If you do need mitigation you will have the data to design an appropriate system.

Well, I was going to respond, but Tom just said what I was going to say.

One other thought, though. You can sometimes get dramatically better results by putting the pipe near the center of the basement slab instead of off to one side.

BTW, I've never even tested my home for radon.

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So many questions, but one in particular that has not been asked...

How and with what are you testing the level of radon in the home?

Are you using canisters? If so, then how many?

Are you using a CRM? If so, when was it last calibrated?

Are you using one of those radon testers for homeowners that plugs into a wall outlet?

Did you do install the system yourself, or did a radon mitigation contractor do it?

Take some pictures of the system, including the fan and the end or termination of the PVC pipe.

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I agree that in most cases, provided the system is installed right, the radon levels are reduced pretty quickly. That's assuming that there is good communication under the slab. The substrate materials used in most newer construction leave enough air gaps for good communication, IE stone gravel.

However, in some older construction, there could be less chance for air to move under the slab. It could be due to the substrate material used at the time of construction. The substrate gaps can also be filled by water moving sediments in over the course of time. A wetter less porous substrate is not going to communicate as well in the beginning as it will after time has allow the system to dry things out.

I stand by my statement that in some cases, it will take more time for the air movement to dry things up. In these cases, the radon systems will gradually improve in ability to pull the radon gases out. It may or may not be the case in this instance but I believe the point is still valid.

I also agree with the other ideas listed in this thread.

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