Help Me Build a Thien Dust Separator

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Forum topic by tool_junkie posted 03-10-2012 06:39 AM 4225 views 0 times favorited 8 replies Add to Favorites Watch
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325 posts in 2526 days

03-10-2012 06:39 AM

Hello All,

I have been using a shop vac for saw dust collection and it is time to have a better dust collection mechanism. I want to build a Thien dust separator using a 5 gallon plastic bucket, but I don’t know what size pipes should I be using. My Shop vac’s pipes are 1.5” in outer diameter. I looked around Harbor Freight and the local wood working shop and both places sell hose connectors in 4” and 2.5” sizes. Which one should I pick? Given the fact that none of my tools has dust collection port or hose attached to them, what is a good size in terms of connector to start with? Does one size have benefits over the other?

Also, where should I buy the hose from? Are the hoses available at th big box stores? So far I have only been using the shop vac hose and hence such a naive question.

I would appreciate your help.


8 replies so far

View DIYaholic's profile


19620 posts in 2672 days

#1 posted 03-10-2012 07:12 AM

I haven’t build one, yet! But I will try to help.

First off, what size is the inlet on the shop vac? That is the size to shot for. My shop vac is a 2-1/4” inlet reduced to a 1-1/2” hose. So, ideally I need 2-1/4” hose. Your situation is/may be different. In reality any size hose will work (without going to extemes), but there is no point in putting a 4” hose on a 2-1/4” intake, the 2-1/4” restiction is the limiting factor. A 2-1/4” intake with a 2-1/2”hose is fine, not much of a difference.

Restrictions are the down fall to DC. use two 45 degree (as opposed to a single 90 degree) bends whenever possible.

What ever you find, shop vac supplies, PVC plumbing supplies, old vacumm cleaners for that matter, as long as it works, it doesn’t matter. If it works, it works.

I hope this helps!

-- Randy-- I may not be good...but I am slow! If good things come to those who wait.... Why is procrastination a bad thing?

View JollyGreen67's profile


1669 posts in 2760 days

#2 posted 03-10-2012 05:11 PM

Go online to and you will find anything you need for connectors and hoses. Plus, they have free shipping until 6 April !

-- When I was a kid I wanted to be older . . . . . this CRAP is not what I expected !

View tool_junkie's profile


325 posts in 2526 days

#3 posted 03-12-2012 03:43 AM

Thanks Randy and Jim for your reply.

I have a few measurements from my two shop vacs.

First one has an inlet port of 2-1/4” and the other (Ridgid brand, 16 Gallons) has the inlet measuring at 2.66”.

I was thinking that I could possibly use a 2-1/2” hose with reduction to 2-1/4”. I was also thinking that I could use the 2-1/2” elbow and straight pipes from Rockler (

The confusion I am running into is how would I couple the elbow with the hose. I think I would need some sort of 2-1/2” to 2-1/2” coupler whose one end will go into the elbow and the other will accept the hose. But I am not really familiar with the different types of hose fittings and want to ensure I order all in one order from Rockler.

Can you guys please help?


View DIYaholic's profile


19620 posts in 2672 days

#4 posted 03-12-2012 05:32 AM

I have found that the hoses from different manufacturers vary. Trial & error is what I do. I don’t like ordering some things on line & this would fall into that category.

Good luck, keep posting & asking questions.

-- Randy-- I may not be good...but I am slow! If good things come to those who wait.... Why is procrastination a bad thing?

View fussy's profile


980 posts in 3048 days

#5 posted 03-12-2012 09:00 AM

Junkie, use whatever size that comes with your vac. If you need plumbing parts to make the thing, take a hose along to a hardware store (aCE OR BETTER) TO FIND SLIP FITS FOR YOUR HOSE. fOF A lot OF HELP IN BUILDING GO TO THIS SITE AND LOOK AROUND A LOT:

Lots of information there. If you need personal help, pm me with any quesation and I will do my besrt. My shop vac separator is wonderful as is the one in my dc ring.


-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

View 308Gap's profile


337 posts in 3000 days

#6 posted 03-13-2012 10:04 PM

I have found the different shop vacs have different size hoses. I’m staying with the lowes 16gl shop vac since I already had some hose parts. I also picked the one with the highest cfm rating, mines plugged into a dust deputy that works fine for a small shop. Start with the vac you like and use pvc connectors and fernco fittings if needed.

I used to order from for my saltwater reef tank and

-- Thank You Veterans!

View HorizontalMike's profile


7756 posts in 2911 days

#7 posted 03-13-2012 11:09 PM

I have built and used the Thien separator on both my HF and shopvac. I have also used the Grizzly plastic separator on both as well. Each time they were on a standard 30gal aluminum trash can. The Grizzly version worked just as well on the shopvac and at <$30 it is a bargain. FWIW, I also added a Hepa filter to the shopvac and it works great. I have the shopvac dedicated for my Mitersaw DC.

-- HorizontalMike -- "Woodpeckers understand..."

View Grandpa's profile


3259 posts in 2672 days

#8 posted 03-14-2012 01:42 AM

I have bought shop vac hoses and parts at my local ACE hardware. I carried in parts and picked out what I needed. If you can get to some size that PVC will work with, you might get what plumbers call a Hubless Connector ( brand name). Those come with ID’s that match different pipes so it they can be had with different sizes on each end. Just a thought.

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