Can I put a dryer vent duct under a concrete slab?

[rtimgray]

We're planning an addition to the house and will be adding another place to have a washer/dryer. If we locate this in the central portion of the addition, it will be several feet from the nearest outside wall.

I was wondering if it would be possible (or maybe even if it is accepted practice) to install dryer vents under a concrete slab. Our addition will have a concrete slab floor (which is not there yet) and we will be putting plumbing piping beneath the slab anyway. Would there be any issue with adding a duct for the dryer venting?

I have been in homes that had HVAC ductwork in the slab, and I've heard that people aren't too fond of that because of the possiblity of mold or other stuff in vents. However, the dryer vent is just going to be blowing outside. I could run the duct straight so it would be easy to clean out as well (I think).

Any thoughts on material? Would PVC pipe be out of the question because of flammability? I know I see the plastic flexible duct still available, but that doesn't mean its a good idea. I'm afraid that metal ducting would rust and corrode and cause more problems. Maybe flexible metal inside of PVC?

Any suggestions you guys would have would be appreciated. Thanks.

 

[rtimgray]

From what I've read in a quick Google search, looks like PVC is frowned upon because of both breaking down from heat and static electricity/static cling to lint. What do you guys think about putting metal ductwork down under the slab? If I use aluminum will it still eventually corrode or will it live forever?

Thanks again.

 

[rambler]

Condensation would be a big concern. You are blowing out hot wet air, typically a very short pipe is best.

Now you are running the pipe through several feet of burried pipe at 55 degrees year around. That's going to condense all the water out of that hot wet air.

I wouldn't try it unless you can slope it downhill and no gooseneck on the end, so the water can run out the end. Don't really know, but just on first thought, I'd think there would be lots of issues.

--->Paul

 

[WM75Guy]

Here is how they did mine with pvc in the slab and a metal elbow in the laundry room to connect to. That side of the house had about 2' of exposed concrete above the grade.

 

[rtimgray]

Here is how they did mine with pvc in the slab and a metal elbow in the laundry room to connect to. That side of the house had about 2' of exposed concrete above the grade.

How long have you had your vent in place? Are you seeing any issues with either condensation or lint buildup?

Incidentally, what line size is that and how long of a run is it? Did you slope the vent downhill to let any condensation drain out?

Thanks for the pictures. That helps alot.

 

[SandburRanch]

We're planning an addition to the house and will be adding another place to have a washer/dryer. If we locate this in the central portion of the addition, it will be several feet from the nearest outside wall.

I was wondering if it would be possible (or maybe even if it is accepted practice) to install dryer vents under a concrete slab. Our addition will have a concrete slab floor (which is not there yet) and we will be putting plumbing piping beneath the slab anyway. Would there be any issue with adding a duct for the dryer venting?

I have been in homes that had HVAC ductwork in the slab, and I've heard that people aren't too fond of that because of the possiblity of mold or other stuff in vents. However, the dryer vent is just going to be blowing outside. I could run the duct straight so it would be easy to clean out as well (I think).

Any thoughts on material? Would PVC pipe be out of the question because of flammability? I know I see the plastic flexible duct still available, but that doesn't mean its a good idea. I'm afraid that metal ducting would rust and corrode and cause more problems. Maybe flexible metal inside of PVC?

Any suggestions you guys would have would be appreciated. Thanks.

If you can run it to drain as mentioned I see no problem. But if possible use a full length pipe so there aren't joints to collect lint. According to some research pvc Softening Starts, (approx.) 250°F
Material Becomes Viscous 350°F

The only way I see heat being a problem is if the upper limit switch on the dryer fails to function correctly and in that case the house will probably on fire and not the vent pipe.

For cleaning, install a small stainless cable in the pipe and on occasion pull a bottle brush through of correct size, similar to cleaning a flue pipe. Or get more serious and pig the pipe with a foam pig and the shop vac.

I have pvc duct pipe under the slab for HVAC and see no problems with that in the past 28 years.

 

[WM75Guy]

We had that house 2 years before we moved. It was sloped well, 1' drop in a 15' run, I never had a problem with it clogging up. The ones that run up the wall to the roof I seemed to have to clean those out as gravity causes buildup of lint and condensation. I designed our new house so the laundry is on an outside wall, the vent runs straight thru the wall to the outside.

 

[Brad_Blazer]

How about SS duct and wrap it in insulation? For some reason stainless duct is hard to find but Mcmaster has it.
McMaster-Carr

 

[PILOON]

I would not use aluminum in the concrete as a chemical reaction will soon eat it up .
Concrete emits salts which react with aluminum.
Plastic, eg PVC would be the way to go however use a metal lead from the drier to the ducting, at least for the first 3 ft or so in order to dissipate heat B4 it enters the PVC ducting section.
Naturally SS would be best, but pricy.

 

[CurlyDave]

Sooner or later this vent will need maintenance or repair.

I think you will be far better off to run it up through a 6" stud wall and out through the attic.