I am building my ductwork out of 6" PVC drain pipe. The only problem I have
had is in the locations that I have used flex lines to complete a drop. How
have others joined the flex line to the PVC? It fits inside of a PVC
fitting, but will not go on the outside of a pipe so that it can be clamped.
My best solution so far (that I am not thrilled with), has been to buy 6"
metal duct fittings (maybe called starters or stubs IIRC). The ones I used
come flat and you snap the ends together into a round fitting. I have
inserted the finger side into my PVC pipe and run a few screws through some
of the fingers. The flex line fits the other side well enough with a band
clamp. My biggest complaint is the deformity and possible potential for
turbulence where the fingers enter the pipe, as well as the fact that the
flange that divides the finger side from the solid side is slotted and
allows leakage. I suppose the leakage can be alleviated with duct tape, but
I was wondering what others had done.
This is what I did - seems to work well.
I have a run along the wall w/ blast gates that drop down.
After the blast gate I have a about a 12" peice of PVC. I made a few cuts
in the end that will connect to the flex about 4-5" long (I did 8 of them,
did it on the band saw - push into the blade - rotate - push into the blade
rotate..etc..) enough to compress it a bit to get the flex to fit over it -
secure w/ a band clamp and it works great.
Its a PITA and you will have to wrestle w/ it a bit to get it on.
A few others I had some "inside" couplers from my old system that worked ok
Can't you reduce to 4" for the flex duct. I don't think the losses can be
worse than any other method used to attach the flex duct. IIRC, my flex duct
fit right over the 4" PVC. In fact, I would assume that a plumbing supplier
could get a reducing wye that goes from a main 6" trunk line to a 4" drop.
One is listed on this site
http://www.pep-plastic.com/manufacturers/plastinetics/d-wyes.htm , so I know
one should be available.
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