dryer vent

[Chad Fabry]

I inspected a two unit where the dryers (elctric) were vented using 4 inch galvanized pipe. I looked inside and there were no lint deposits and it was pretty smooth walled. 8 foot, straight runs to the exterior.

I noted it, but not as a defect, and now I'm wondering... what do you folks think?

[Tom Barber]

4" metal pipe is the norm here in VA, I don't remeber ever seeing anything else, except for the 4" round plastic which does not work.

Tom Barber in VA

[kurt]

I don't know why 4" galvanized pipe wouldn't be great; any 4" METALLIC duct or tubing is fine w/ me. I always call the plastic ducting a defect/fire hazard.

[hausdok]

Me Too,

The CPSC has been trying to educate folks to the fact that corrugated metal and plastic outlets from the back of dryers are fire hazards since about 1996 - 1997. CPSC recommend replacing all corrugated outlets with smooth-walled, metal box-vents (Cost about $20. at home centers) and the vent from the outlet the its terminus with smooth-walled metal vents that have been taped with heat-resistant foil, not screwed together, at joints.

CPSC found that over a 3-4 year period there were more than 15,000 fires started in the U.S. from lint fires caused by corrugated ducts.

ONE TEAM - ONE FIGHT!!!

Mike

[chrisprickett]

Smooth wall metal pipe is fine, as long as the total length is under 25' long, subtracting 2 1/2' for each 45 degree bend. No screws are allowed as fasteners. I will note anything that exceeds 15' as a maintainance issue.

[Jim Katen]

Originally posted by Chad Fabry

I inspected a two unit where the dryers (elctric) were vented using 4 inch galvanized pipe. I looked inside and there were no lint deposits and it was pretty smooth walled. 8 foot, straight runs to the exterior.

I noted it, but not as a defect, and now I'm wondering... what do you folks think?

Sounds like a great set up. You know it isn't going to become crushed or come apart at the seams like a duct might. And if a fire does start in there, it certainly won't burn through the pipe & spread. In fact, it'll probably burn itself out before it damages the pipe.

Maybe I'll install a pipe on my own dryer vent. . .

- Jim Katen, Oregon

[crusty]

Our legacy UBC requires it and only allows 6 ft of flex as does the IRC I believe (sorry too lazy to check it.) One problematic area worth noting is backwards installation where lint can start collecting at the joints. The male ends should be pointing downstream.

[Jim Katen]

Now hold on a second. I figured that Chad, being the techy sort of guy that he is, meant "pipe" when he said "4 inch galvanized pipe." As in a thing that would break your toe if you dropped it on it.

But everyone's responding as if he meant "duct". As in 26 gauge sheet metal. Which is it?

- Jim Katen, Oregon

[Chad Fabry]

pipe

[Jim Morrison]

Originally posted by Chad Fabry

I inspected a two unit where the dryers (elctric) were vented using 4 inch galvanized pipe. I looked inside and there were no lint deposits and it was pretty smooth walled. 8 foot, straight runs to the exterior.

I noted it, but not as a defect, and now I'm wondering... what do you folks think?

Sounds bombproof to me.

[crusty]

[:-bigeyes

[Neal Lewis]

Chris,

Where does the 25 ft rule come from. My Maytag gas dryer installation manual has a chart of the maximum distances for smooth wall 4" duct. It states a whopping 65 feet with no elbows and 28 feet with four ninety degree elbows.

[hausdok]

Hi Neal,

Well, in your case the manufacturer's listing and labeling supercedes the code. Without the manufacturer's specs, it really depends on what code your municipality is using. The IRC says, 25ft. max minus 2-1/2 ft. per 45 degree bend or 5ft. per 90 degrees [iRC 1501.3,2437.c]. The UMC says 14ft. max including two 90 degree bends minus 2ft. per additional 90 degree bend [uMC 504.3.2].

ONE TEAM - ONE FIGHT!!!

Mike

[chrisprickett]

Neal,

What Mike said. The crappy Roper dryers say only 4' of vertical. I mostly comment on new construction inspections, and go by the IRC.

[Bain]

The 25' rule minus appropriate distances to accommodate for bends was addressed by CABO back in '92. Not adhering to this can cause lots of problems in houses where the laundry room is near the front wall of a second floor, and the duct sustains multiple forty-five or ninety degree bends. Of course, it can't be redirected without removing drywall or slicing a hole in the front wall of the house.

John