rushing air noise in PVC pipe

[blockmanjohn]

Hello, my name is John and I am new to this forum. I hope some one can help me with a small problem I have. I recently installed a sub slab depressurization radon mitigation system in my house. I am using 4 inch PVC from below the slab to above the roof with a Fantech HP fan inline which is located outside of the house. All is well, but there is a very noticeable rushing air noise in the 8 foot long pipe section in the basement which starts under the slab and exits out the rim joist. Is there some way to cut this noise down? I was thinking of wrapping the pipe with insulation but I don't know if this will work, or if there might be a better way. Also, even though the fan is located outside the house, I an still here it on the inside. I have it isolated with rubber connectors, but it is still very noticeable. Any help for that? Thank you in advance, John.

[Bill Kibbel]

I've inspected thousands of homes with radon mitigation systems. I have to practically put my ear to the fan housings to know if the fans are running. The only times there have been any noticeable sound is when water is being sucked up into the system. It sounds like my kids trying to suck up the last drop of a milkshake.

What's the CFM of the fan?

[blockmanjohn]

The cfm of the fan is 157 at 0 inches W.G. . It sounds like for one reason or another the airflow is too high. Maybe an opening in the system some where. I have a gauge to measure inches W.G., but I haven't installed it yet.

[Scottpat]

I agree with Bill.... When you put the pipe into the slab did you remove as much dirt as possible and place a bed of crushed rock in the hole and then place the pipe and back fill with crushed rock and then seal with concrete?

My experience with water in the pipe is that it will make a gurgling sound from time to time.

[blockmanjohn]

I installed the pipe before they poured the slab. There is 6 to 8 inches of gravel under the slab. The sound in the pipe is a rushing rather than gurgling sound.

[Erby]

You think yours is bad, listen to the one in the video on my blog.

Radon Mitigation System Malfunctioning Video

What type of pipe did you use?

Did you seal the cracks in the basement that would let it suck air out of the basement instead of from under the slab?

Probably ought to get that gauge put on and measure whether or not it's actually pulling any air.

Like Bill, I've looked at a lot of them and hardly ever hear any noise IF it's installed and operating like it should.

[blockmanjohn]

I used ABS pipe. Today I installed the manometer and it read 1.5 inches. According to Fantec that translates to about 46 cfm for my model fan. Does this sound about right for a fairly tight and intact 1200 square foot basement slab? Thanks for your replies, John