# Anyone run 2 Dryers, using 1 duct? or not safe?



## beenthere

2 vents.

The duct is too small for 2 dryers. So you would decrease drier ability.

When one dryer was running, it would push exhaust back into the other one.


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## dac122

been is right you need to run another vent due to size and cross drafting into the other dryer. Check with you local codes as they will spell out what restrictions you must adhere to and what options you have.


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## bunjamins

*beenthere and dac are generally right, but...*

If you have a 4" dryer vent pipe you should probably not do two on one vent, it also depends on your dryer. If you're lucky enough to have 6" duct work or bigger you can use a single duct to duct multiple dryers, laundromats all do it, you just need an all-metal back draft damper between each dryer and the union of exhaust pipes. Once hooked up you can test to make sure back pressure isn't too much by running both dryers and testing pressure using a inclined manometer (not too expensive.)

Here's a nice document from whirpool that explains it better:
http://www.ajmadison.com/ajmadison/itemdocs/W10100920.pdf

I am dealing with the same thing right now, two dryers that need to vent to a very conspicuous patio area on the front of the house, I really don't want to have two vents where one slightly larger vent might work. Hope this helps!

edit:
found this which might also be helpful:•	Manifolding of two or more dryers is most efficient with a gradual upsizing that maintains exhaust velocity without increasing backpressure. Two dryers cannot function on the same sizing exhaust as one. The best rule of thumb is manifolding (horizontal) is to allow 12 square inches of cross section plus 10%. The following is recommended:
2 dryers 12”x 2 = 24 + 10% = 27” or 6” round
3 dryers 12”x 3 = 36 + 10% = 40” or 8” round
4 dryers 12”x 4 = 48 + 10% = 53” or 8” round
5 dryers 12”x 5 = 60 + 10% = 66” or 10” round
6 dryers 12”x 6 = 72 + 10% = 80” or 10” round


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## ehoez

omg, thanks man......


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## nap

bunjamins said:


> If you have a 4" dryer vent pipe you should probably not do two on one vent, it also depends on your dryer. If you're lucky enough to have 6" duct work or bigger you can use a single duct to duct multiple dryers, laundromats all do it, you just need an all-metal back draft damper between each dryer and the union of exhaust pipes. Once hooked up you can test to make sure back pressure isn't too much by running both dryers and testing pressure using a inclined manometer (not too expensive.)
> d


Not sure but I believe backdraft dampers in a dryer exhaust are prohibited by building codes other than a flap damper at the outside exit.

They would tend to catch lint and if the codes are picky enough to disallow screws to connect pipe sections together, I would think that a damper would not be allowed either.


also, in multi-vent installations in commercial situations, there are often, if not always, requirements for a booster fan to be sure there is an exhaust flow and one dryer will not push back into another dryer.


It would be best for OP, or anybody, to check their local building codes. There really are a lot more rules on a dryer exhaust than one might think.


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