Griz G0441 - how to transition to 6" pvc?

[Wade Lippman]

Based on everyone's input in my poll, I have decided on PVC. I will be reworking my system as I buy new machines, so something easy to take apart is important. (planning ahead is not an option, I am not capable of that....) I was concerned about the static electricity, no one who has PVC is really troubled by it.

So, my plan to is to put a 8" 90 elbow on the inlet, 2' of 8" steel to the ceiling, a 8" 90 elbow to go horizontal (I know elbows are bad, but figure that if I do them in 8" it won't be as bad) an 8" steel Wye to each side of the room, and then change to 6" PVC to get to the machines.

I can use a metal connector that is crimped at both ends, but then I would have the air going into a crimp which I know is a big no no. So how do I transition? A Fernco flexible connector would avoid the crimp, but isn't very rigid.

So how do you transition from 8" metal to 6" pvc?

[Paul Wunder]

If you support the pipes at the joint where the Fernco is rigidity should not be a problem. 6" 2729 PVC is pretty rigid and only requires support at the end of a straight 10' run or at turns or wyes. I put up far fewer supports than I thought I would need, I did put two 1/2" sheet metal screws at each joint (no caulking, etc.)

[robert morrison]

From a theoretical standpoint, you do not want to crate turbulance in the airstream right before the air enters the cyclone as it would reduce the seperation efficency. It would be better to have at least 2' or better yet a 4' straight pipe coming off the cyclone inlet. Then do an adjustable elbow set at about a 45* angle toward the ceiling followed by a 2' straight pipe, and then another adjustable elbow set at 45* to transition back to horizontal at ceiling height.


When you want to reduce from 8" metal to 6" plastic use a metal reducer to go from 8" metal to 6" metal. Cut two flat pieces of 1" to 1.5" thick wood about 10" to 12" square. Cut a hole centered in in each piece the diameter of the outside diameter of the 6" metal reducer and the other one the diameter of your pvc. Use three 1" sheet metal screws to screw from just inside the edge of the pipe thru the pipe and into the wood. A little duct (master sealent caulking tube home depot) sealant can transition any slight diffrence in diameters. Use 4 bolts to bolt the two wood pieces together. The wood also works to put hooks into to help hang the pipe.

[Wade Lippman]

I have a really slick circle cutter so making the wood pieces will be easy; however I have read that sharp diameter transitions are bad. Is that wrong?

I intended to come out of the dust collector at a 45 and go up to the ceiling to another 45, but that will hit the ceiling in a bad place and make where I put my lathe a serious mistake. Like I said, planning is not my strength. I will either have to move everything around or chance the turbulence.

At my old house I had 5" flex going to a 90 elbow right into the inlet. Couldn't have been set up much worse; and it was a much shorter cyclone. Yet separation was pretty good. A full 55 gallon drum only put a couple cups of dust in the filters. I know people say they get tablespoons, but I can live with a couple cups.

[robert morrison]

You could use a 8" to 7" reducer then a 7" to 6" reducer. But, both reducers have about a 45* transition angle.

A 8" x 6" x6" wye that looks like this http://www.homedepot.com/h_d1/N-5yc1...&storeId=10051 provides a smoother transition. You just have to run 8" untill you get to the point where you want to branch off a drop or to add another branch.

It would be a royal pain, but you could take a 2' long straight pipe and rivet it together in a cone shape 8" on one end and 6" on the other. I would not attempt this.

[Wade Lippman]

A 8" x 6" x6" wye that looks like this http://www.homedepot.com/h_d1/N-5yc1...&storeId=10051 provides a smoother transition. You just have to run 8" untill you get to the point where you want to branch off a drop or to add another branch.

Yes, that does give a nice long transition, and it is certainly cheaper than buying a 8" Wye and two 8"-6" reducers; BUT it does the change to PVC (or even the continuation with steel) with the air flow hitting a crimp. I though that was costly. Am I making too much of the crimp?

[Bas Pluim]

I used one of these, it is not crimped. You may need to crimp the 8" end yourself, but that is not going to affect the airflow.

[Joe Angrisani]

.....BUT it does the change to PVC (or even the continuation with steel) with the air flow hitting a crimp. I though that was costly. Am I making too much of the crimp?

You are, compared to your plan to put two turns right at the inlet to the cyclone. I'd think THAT will mess up the airflow far more than a crimp's wee lip.