PVC Dust Collection: Fittings and Adapters for a 6 in. Trunk Line

Matthew Peech is running an overhead dust collection system through his whole shop using PVC sewage pipe: a 6 in. trunk line connected to a two horsepower dust collector, with 4 in. PVC drops. Before installing it, he covers where to start and which fittings to buy.

The sizing mismatch

Standard 4 in. or 6 in. sewage PVC is not the same size as dust collection pipe. It also doesn't match the 4 in. ports on mid-industrial equipment such as shapers, joiners and planers, and the fit wobbles. His fix is an adapter, sold by Rockler, that fits over a dust collection fitting on one side and takes 4 in. sewage PVC on the other. He says they are only a few bucks and recommends ordering several.

Why remove the collector's splitter

A 1.5 or 2 horsepower collector typically comes with a fitting that reduces the 6 in. suction port and splits it into two 4 in. ports, because most equipment has 4 in. ports. He took his off and runs a 6 in. trunk line instead, which he says increases suction. He drops to 4 in. only where needed, and uses as little flex line as possible to limit drag.

Blast gates

The system will serve several machines through blast gates. He says there are online calculators for checking whether a collector can handle a machine. Blast gates are mostly made for flex line or adapters, so the same outside and inside diameter problem appears. With an adapter fitted, the PVC goes on fairly tight.

A 6 in. tip

The 6 in. outlet doesn't seal against the pipe either. He found that the 6 in. splitter taken off his collector fits perfectly into the flange already on the end of 6 in. sewage pipe, which can save several adapters when converting from 6 in. to 4 in.

Sweeping fittings

Ninety-degree fittings are a bad word in dust collection. If one is needed, use a sweeping or long 90, not a straight 90, which kills suction. The 4 in. fittings aren't bad in price, but 6 in. ones get expensive; a sweeping 6 in. tee is about 40 bucks. A sweeping tee keeps air flowing in the direction of the collector, unlike a straight tee.

The installation, issues, blast gate placement and a test are promised in the next video.