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I need to vent a gas fired clothes dryer in the garage of the house that I am renting out. According to one web site:
“The International Mechanical Code article 504.6 stipulates the requirements for Domestic clothes dryer ducts. In brief, the maximum length of duct permitted is 25 ft. This maximum length should be reduced by 2.5 ft for each 45-degree bend and 5 ft. for each 90-degree bend. The duct should be a minimum nominal size of 4 inches in diameter and shall have a smooth interior finish.”
I am about 600 miles away from the place at present, but my memory seems to indicate that I will need to have a vent pipe run of close to 20′. I was wondering if anyone has any suggestions as to the optimal vent pipe size. While I assume that the 4″ will work, I was wondering if a larger size would build up less back pressure. Of course, going too large would mean that there would not be enough air flow to move the lint through the pipe and it could result in a plugged pipe.
Is 4″ optimal, or should I go larger? What is the best and/or most reasonable pipe to use for this application?
Replies
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Casey,
Most, if not all, dryers are shipped with a 4" duct connection. I would just stay with that size and use the smooth wall pipe that can be assembled in 3 to 5 foot sections. After a period of time you will have to disassemble to remove the caked on lint. There's really no way to get around that unless you have an in-line secondary lint filter, which you will have to remember to clean out all the time. That also slows down the air flow and increases the drying time if not maintained. It also doesn't catch all the fine lint and you will still have to clean the pipes, although at a longer interval.
I ignored my pipes (8' straight up and 12' horizontally) until my wife complained about the damp clothing and the length of time it took to get the job done. Had about a 50% clog throughout the length of the horizontal pipe with a severe matting of the lint on the bottom half of the interior circumference. Ten minutes to disassemble, ream it out with a rag on a broomstick and reassemble. Good to go for another 10 years.
*I would stick with the 4 inch since thats the standard exhaust size on the dryer itself and making it bigger wouldnt really do anything except to add more back pressure.I use my gas leaf blower to clear out the dryer vent and just put a rag around the inside with the blower to seal it real good and it works flawless, try it.
*You need to speak with Fan Tech, which makes booster fans for dryers. A really great product. Get an auxilary lint trap from them for $20. It will save the broomstick and leafblower drill that Ralph and Chris experienced.http://www.fantech-us.com/dryer_boosting.htm
*Casey,I had a similar problem with my laundry room/dryer. I live in a split level and the design puts the laundry room in the middle of the basement. I had a vertical rise of about 9 feet and a run of about 8 feet. I used the flexible duct for a long time and it finally clogged. I choose to run thin walled 4 inch pvc, it is smooth on the inside and relatively easy to work with. I connected to the dryer with a piece of the flex and stretched the other end over the pipe. It was a little tight in the ceiling but the rooms were unfinished at the time. I have had no problems. I clean out the piece of flex once a year or so. I glued the vertical pieces together and screwed the horizontals together glue would probably be okay but I would blow the duct out with compressed air before I ran the dryer.
*Casey,Be careful of using PVC for moving air. Moving air in PVC can cause a build up of static electricity which can cause nice size arcs at the ends. I would guess that the moist air from the dryer "shorts out" the static under most cases but if the dryer were left running after the clothes were dry you could have this condition. I heard some horror stories from people who used PVC for a dust vacuum system for their wood shop and lit the sawdust on fire.
*Now I am worried!!! In our remodel, we used 4" pvc pipe at a total length of about 22 straight feet, with out any booster fan in it. And, the pipe drops down from the dryer about 2 feet before taking a "soft" right angle where the 22 foot length is.Are we gonna have arcing, have trouble getting our clothes dry, and have to use a super long telescopic pole to get at any lint from the outside up to the right angle?? It's too late in our case ...... everything's closed in!!Uh-oh......
*Dee VeeBe worried, be real worried. The next thing will be that you will find out that the moon is made of green cheese and that on the man'd landing on the moon that some lab mice escaped and the moon is about to be all eaten and the remains crash into the earth.
*Stevei I heard some horror stories from people who used PVC for a dust vacuum system for their wood shop and lit the sawdust on fire. b OCT - Old carpenter's tale.Much worse than old wife's tales.That has been debunked so manytimes. First the static problems have been researched and debunked. And fire marshals, makers of metal ducting, fire protection association, insurance companies have been asked to document a case of a fire caused by dust in a plastic duct in a home/small workshop and there have never found a case.
*Fire in dryer vents is a very real hazard. Most of the replies mentioned cleaning the duct at least once per year. 90% of the people never think about cleaning thier dryer vent. More fires are started with clothes dryer lint than PVC pipe.
*Casey,You mentioned the IMC, section 504.6. Check out section 504.1- "Clothes dryers shall be exhausted in accordance with the manufacturer's instructions." If you have these, follow them.Is 4" optimal? In your case, no. Use 5" galvanized. PVC is not a suitable duct material, no matter anyone else has installed. Your 20' run include the vertical rise? 2 90's gets you up to 30'. 5" costs about the same as 4 and is readily availble at most home centers.
*You all make me glad I put my dryer against an exterior wall. The vent pipe is less than a foot long.
*Joe, your email doesn't work. Wouldn't be more appropriate for a woodworking site?
*Hi Guys,Like I said I have'nt had any noticable problems with arcing and no problems with getting the clothes dry, I guess static buildup could be a concern. My reno. is'nt done yet so I may change it, in the future.C
*The current Fine Woodworking Shops and Tools (? or titled something similar) has an article on the danger of a static spark causing an explosion in a home workshop dust collection blower system with duct work from 4" PVC. It was written by an MIT mathematician (and woodworking hobbyist) working with an MIT physicist. The conclusion was that while it is not impossible for there to be a static spark, it is highly unlikely. The author said that after his study he installed PVC ducting for his dust collection system in his workshop. I would guess that in a drier vent, the velocity of the air would be lower and the air would be more moist which would make a static spark even less likely. My concern with PVC pipe would be what would happen if (when) the lint catches of fire from other causes, such as spontaneous combusion. I would guess that a typical PVC pipe would not do too well if a significant amount of lint in the pipe combusted.
*Hi Casey,I thought about that too, but what about the flexible plastic duct, you know el cheapo, it probably would'nt fare any better.C
*I guess metal probably is the best, I will probably change mine in the future.c
*Flexible plastic vent should not be used to vent dryers. It is not designed for it, the manufacturers do not allow it, and it's fire hazard (confirmed to me by several fire fighters.)Other than that, it's great stuff. Works particularly well on houses with vinyl siding
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I need to vent a gas fired clothes dryer in the garage of the house that I am renting out. According to one web site:
"The International Mechanical Code article 504.6 stipulates the requirements for Domestic clothes dryer ducts. In brief, the maximum length of duct permitted is 25 ft. This maximum length should be reduced by 2.5 ft for each 45-degree bend and 5 ft. for each 90-degree bend. The duct should be a minimum nominal size of 4 inches in diameter and shall have a smooth interior finish."
I am about 600 miles away from the place at present, but my memory seems to indicate that I will need to have a vent pipe run of close to 20'. I was wondering if anyone has any suggestions as to the optimal vent pipe size. While I assume that the 4" will work, I was wondering if a larger size would build up less back pressure. Of course, going too large would mean that there would not be enough air flow to move the lint through the pipe and it could result in a plugged pipe.
Is 4" optimal, or should I go larger? What is the best and/or most reasonable pipe to use for this application?