Weird idea

[HeyBub]

Any reason one can't use 4" PVC sewer pipe for dryer exhaust piping?

I've got to go UP 8 feet (which will be metal), then horizontally about 20' to get to a soffit. For the 20' run I'm considering the sewer pipe (not the kind with holes) because it's easier to work with.

Goblin roofers didn't replace the roof vent when they put in a new roof, I didn't notice their failure for a LONG time, and now I'm endeavoring to correct the problem. I figure a soffit vent is going to be easier than dealing with a retrofitted roof vent.

Suggestions welcome.

[Doug Miller]

It's combustible... That a good enough reason?

[Bewildered]

Is it combustible at temperatures of dryer exhaust? PVC burns, but it isn't easy to ignite.

[Doug Miller]

I don't know, and I don't want to find out -- since it releases poisonous gases when it burns. I'm gonna stick with metal duct for dryer vent.

[DerbyDad03]

Combustibility, lint and static electricty. Sounds like a fun combination.

Here's something pretty funny that I found at

First the author (a "Nationally Syndicated Newspaper Columnist") says there is no reason you can't use PVC, then adds that the manufacturer might not want you to because it's combustible! So, according to him, unless your specific dryer manufacturer says not to use PVC, it's OK.

"I have had to use four inch PVC pipe on occasion to vent dryers through roofs. ... There is no reason why you can't use plastic pipe to vent your dryer unless of course the manufacturer says not to. When I did it, there were no restrictions as to using PVC material. There is an outside chance that a manufacturer may not want you to use it because the pipe is actually a combustible material. I would talk to the local fire department and see what they say......"

HeyBub wrote:

[hallerb]

that runs way too long it will reward you in bigger bills and slower drying let alone occasional lint clean out.

dryer vents should be as short and straight as possible

[Joseph Meehan]

Well some places sell cheap plastic flex hose for driers. That is a bad idea. They collect lint nicely.

The idea that it is OK because the manufacturer did not prohibit it, is a very poor argument. How many of you have ever read not to put water in the fuel tank of your car rather than gasoline? They can't predict all the foolish things people will think of.

As for PVC, I really don't know. I can see some advantages, but I also see some potential problems. Considering using standard materials works and the possible results (like death) for using the wrong materials could be serious, I will stick with standard tested materials.

[Willshak]

[DanG]

You are at or exceeding the maximum distance for residential dryers. Check your particular model. Each fitting and turn require a reduction in distance.

There is some good information here:

you might note they do NOT recommend PVC due to static/lint issues.

[terry]

. Plastic is combustible Recently replaced our flexible plastic dryer hose with a flexible metalized one. Although our insurance companies require metalized as part of new installs they do not necessarily tell you to replace the plastic of existing installations. Our flexible hose connects to a length of galvanized tin pipe duct identical to that used for gutter drains. The thin Al of the new hose is very delicate and perforates more easily than the plastic skin of the old flex. hose. BTW you can get light weight aluminum some of which comes flat with edges that you snap together into a pipe after trimming it to length with metal shears. Also there are 45s and 90s that are completely rotatable which makes offsets and other angles such as getting over a truss joist or into a soffit area much easier. We used that for our bathroom exhaust. One thing we found with bathroom exhaust duct in cold attic was condensation; it may be wise to slope exhaust pipe downwards toward outside. In cold weather a little 'beard' of frozen moisture appears on the lip of the exhaust outlet. That moisture can drip through joins onto ceiling insulation and ceilings. However the hotter exhaust from a clothes dryer may avoid this.

[Harry K]

That is an extreme length for ducting a dryer.

As for easier to work with? I see very little difference between the galv. metal and pvc. One needs a hacksaw to cut it with the other tinsnips. One uses glue, the other just slips together. Haven't checked prices recently but at a guess I suspect galv would be cheaper.

As for the 'combustibility' warnings. I don't think it would really be in play minus a real fire to begin with. There is softening with heat though.

Harry K

[Steve Barker LT]

28' is not extreme. According to the chart at some models allow 60 or more feet.

[hallerb]

I was really afraid of fire from that cheap white plastic durable flexible easy to use vent pipe thats no longer on the market because of fire risks.

a friend replced his with the new junk foil type.

i brought his old line home it was in his trash and tried setting it on fire on the driveway.

it wouldnt burn. at most it might support combustion barely.

even with direct ignition from my mapp gas torch it wouldnt go on fire just smolder and go out immediately when torch was removed.

personally i think it was safe.

kinda disappointed me with fire hose at ready nothing to put out:(

[butwhat]

There are dryer vent booster fans for sale for situations such as yours.

[e-mail] wrote:

[hallerb]

PVC Ducting

While PVC tubing looks like it would be ideal for dryer venting being rigid and perfectly smooth, numerous technicians report that some sort of static effect seems to take place during use which causes lint to adhere to it, eventually leading to blockages. It may be best to avoid this material for this application if you can use rigid metal ducting instead

[George E. Cawthon]

Manufacturers have to allow for every possible stupidity and lack of maintenance. I have used the plastic flex hose and it works fine; I clean the duct and the inside of the dryer housing periodically. Currently replaced the split plastic with thin metal flex, primarily because it was cheaper. A normal operating dryer isn't going to cause a problem, but if you use corrugated anything you have to clean the piping as it collects stuff. If the lint catches fire, it will burn or melt the plastic.

I don't see the OP's sewer pipe causing any problem since the temperature will be down as it would be 8 feet away from the source. OTOH, a 20 foot horizontal run is a concern unless he has a booster fan in the tube.

Never had a dryer that wasn't located close to an outside wall, usually 2-3 feet of tube to the outside. I would consider moving the dryer so that it would be next to an outside wall; sounds like a poor house design. But then I wouldn't consider an AC unit in the attic, a non-vented stove exhaust, seven smoke detector tied together, and a whole lot of other ill conceived ideas.

[Edwin Pawlowski]

Most plastics used in buildings are made with non-flammable materials by use of additives.

[Edwin Pawlowski]

Some are, most used in building are not. Fire retarding additives have been around fo rmany years.

[Thomas D. Horne, FF EMT]

I cannot speak to the results you got in this specific case but the general concern is that the smoke contributed rating of plastic ducting is extremely high and that the resultant smoke is far more poisonous than that given off by ordinary combustibles. The "form of material first ignited" is likely to be cotton lint rather than the ducting itself.

[Bob]

A potential problem is that the PVC pipe will not heat up enough to evaporate water that causes lint to cling to the pipe. Lint buildup would be a major concern.