How Do We Choose The Spot For Our Initial Suction Point?

A question we often get is: How do we choose the spot for our initial suction point?

Let’s look at some of the factors that influence radon mitigation suction point placement.

Step 1: Evaluating the Home

This house was built in 1975 and does not have drain tile.

It has an attached garage and a front step area that probably has its own foundation zone. These two factors could be potential spots that we might need to mitigate, but not very likely, in this home.

It has a split entry, and there’s a crawl space with a concrete floor under the entryway. If we look in this crawl space, the far side is the shared wall with the garage. Our radon fan will be in the garage attic, so we will have a pipe going out of that wall.

Outside the crawl space, in the living room, we have a block wall that comes up to about waist height and separates the crawl space from the rest of the living space. So, we’re going to have a footing there.

Step 2: Determining Suction Point Placement

The initial suction point has to be somewhere in the crawl space. We know we will have a pipe from the crawl space to the garage, so we could put a suction point near the garage wall.

Based on the soil where this home is located, we expect to find sand below the slab. If we place the suction point near the garage wall, we will probably get some collateral mitigation into the garage area, meaning the radon system will create negative pressure under that footing and mitigate at least part of the garage. We probably don’t have to treat the garage to decrease the radon in this home. If we are going to get collateral mitigation somewhere, we would rather have it be in the indoor space.

Step 3: Pressure Field Extension Testing (PFE)

To reach the main part of the living space and go under the footing separating the crawl space from the living room, we are first going to run some tests.

To test, we will drill several half-inch test holes in each of the farthest-reaching areas of the crawl space. Then, we will apply suction to one of the test holes. This will show us if we are reaching any of the other test holes once we apply suction. If we are reaching the other test holes, that would be a good indication that it is a good spot to use as the primary suction point.

To do the communication test, we will apply suction to one of the test holes, and we’ll record the numbers on our micromanometers.

We did a communication test on two of the test holes. The one just inside the crawl space gave us the best results. We also tested one in the corner but had negligible results.

Step 4: Determining Additional Suction Point Options

Through the testing, we also found that we do not have much influence outside of the crawl space.

Stitching:

A benefit to having our suction point near the entrance of the crawl space is if we need to stitch to get out to the living room, we could. By pulling up a corner of the carpet in the living room near the crawlspace, we could then core a hole to connect to the primary suction point. This is accomplished by digging a tunnel under the center footing to connect the stitching hole back to the primary suction point.

Additional Suction Point:

We will likely also need a suction point coming up and over the living space into the mechanical room on the other side of the basement. The primary suction point placement lends itself to getting pipe up and over through the floor joists and dropping into the mechanical room without it being seen in the living space.

Step 5: Core The Hole For the Primary Suction Point

Now that we have a plan for our primary suction point, our next step is to core the hole in the floor and dig the suction point. Then, we will rerun diagnostic testing with our 2-inch pitot tube. 

And that’s how we choose the location for an initial suction point. If you are looking for radon system service or installation and are in the Minneapolis, MN, area, contact us here.