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Replacing 4" PVC with 6" metal for dust collection ducting--Some Things I Learned

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Forum topic by CharlesA posted 02-01-2021 12:04 AM 608 views 0 times favorited 13 replies Add to Favorites Watch
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CharlesA

3462 posts in 2851 days


02-01-2021 12:04 AM

Topic tags/keywords: dust collection

I just upgraded my dust collection system:
  • replaced home-made Thien Baffle with Super Dust Deputy XL
  • replaced the main trunk line of 4” PVC with 6” metal pipe
I’m no expert, but I thought I’d pass on a few things I learned:
  • I went with metal because 6” PVC is expensive, heavy, and I don’t have access to a lot of fittings.
  • Unless you know you have a good, sharp pair of tin snips, get some new ones.
  • When I use PVC, I can put together with minimal attention to the joints because they are pretty close to dust tight just from a friction fit. I often put in one screw just to keep it together until I’ve decided I like the layout, then I’ll put on some alumininum tape or whatever, but works well without much work.
  • Assembling the metal pipe runs in the same manner doesn’t work at all. I put in three screws into every joint—one just gives you a joint with huge gaps. Then, putting it together is only half the battle—sealing up all the joints is the second part of the installation.
  • If I had to do it over again, I would seal as many joints as possible before assembling (mine is on ceiling).
  • I thought tape was the best thing, but I ended up only using if for the long flat seams on the tubes. For all other joints, I would apply duct mastic, cover the joint with mesh fiber tape, and then dover the tape with dust mastic. When dry it is an air tight, solid connection.
  • I didn’t realize how many seams were in every connecting piece. All those needed to be sealed.

Maybe everybody knows these things—I didn’t. Now, it is done. I think it is better, but I haven’t had much time to test it out. We’ll see.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson


13 replies so far

View menuisierJC's profile

menuisierJC

18 posts in 88 days


#1 posted 02-01-2021 01:47 AM

What kind of metal pipe did you use? HVAC pipe from the hardware store?

Would you post a few pictures? I’m particularly interested in your Y-joints and the main connection to your dust collector.

-- Jeffrey

View CharlesA's profile

CharlesA

3462 posts in 2851 days


#2 posted 02-01-2021 01:58 AM

Yes, Borg metal duct.

I’ll try to take some pics, but not sure I want to show them!


What kind of metal pipe did you use? HVAC pipe from the hardware store?

Would you post a few pictures? I m particularly interested in your Y-joints and the main connection to your dust collector.

- menuisierJC


-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View ibewjon's profile

ibewjon

2348 posts in 3847 days


#3 posted 02-01-2021 02:05 AM

I paint 2 coats of duct sealer down the length of the joint. And also on the 90’s after adjustment and installation. As short of screws as possible to avoid collect long stringy shavings. 26 or even some 24 guage when 26 was out of stock. I use 5” with my 2 hp collector.. I buy the long 90’s, but weld up my own Y fittings to order with a spot welder, then seal with more duct sealer. There are online apps with patterns for cutting the parts for a Y, or a double Y. A great system, and being steel, no shock hazzard.

View tvrgeek's profile

tvrgeek

1754 posts in 2703 days


#4 posted 02-01-2021 02:08 AM

I am in the process of same. That darn spiral duct is expensive. I did not use HVAC duct for the trunk as I have been warned, if you forget and all your gates are closed, you can collapse the duct. Anyway, 6 inch all the way to the TS and BS. Splitting a 4 for the sanders. Dropping a 4 inch right over the table that I can move between the router and TS blade guard. I’ll have a 4 inch port I can put my planer and jointer on. They’re on wheels.

I am a big fan of the foil duct tape. Unlike Duck tape, it is suitable for ducts as the glue does not dry out like the rubber glue does. Easier to re-do as it does not get hard like duct sealing paste or even caulk. Found my self-clearing blast gates leak quite a bit, so they will get a flap of poly tape.

Just added a ClearView cyclone to my Fein vac. Super impressed. Found adapters for my pad sanders and made one from a bit of sink trap PVC for my old Makita belt sander.

Bill Pentz says it really takes a 5 HP, and that needs at least an 8 inch trunk, but I don’t have the power. I’ll see how I do with the 1 3/4. If it is OK, then on will go with the 6 inch Oneida. If not, I’ll get a new 3 HP system.

The hard part is not the DC system, it is the various ideas I have for focusing the airflow through the TS. I was looking at the trunnion and it looks very hard to do any of my crazy ideas except the ramp.

I cut my ducts with my angle grinder. Much easier.

View tvrgeek's profile

tvrgeek

1754 posts in 2703 days


#5 posted 02-01-2021 02:09 AM

I am in the process of same. That darn spiral duct is expensive. I did not use HVAC duct for the trunk as I have been warned, if you forget and all your gates are closed, you can collapse the duct. Anyway, 6 inch all the way to the TS and BS. Splitting a 4 for the sanders. Dropping a 4 inch right over the table that I can move between the router and TS blade guard. I’ll have a 4 inch port I can put my planer and jointer on. They’re on wheels.

I am a big fan of the foil duct tape. Unlike Duck tape, it is suitable for ducts as the glue does not dry out like the rubber glue does. Easier to re-do as it does not get hard like duct sealing paste or even caulk. Found my self-clearing blast gates leak quite a bit, so they will get a flap of poly tape.

Just added a ClearView cyclone to my Fein vac. Super impressed. Found adapters for my pad sanders and made one from a bit of sink trap PVC for my old Makita belt sander.

Bill Pentz says it really takes a 5 HP, and that needs at least an 8 inch trunk, but I don’t have the power. I’ll see how I do with the 1 3/4. If it is OK, then on will go with the 6 inch Oneida. If not, I’ll get a new 3 HP system.

The hard part is not the DC system, it is the various ideas I have for focusing the airflow through the TS. I was looking at the trunnion and it looks very hard to do any of my crazy ideas except the ramp.

I cut my ducts with my angle grinder. Much easier.

Even HD has 45 degree Y joints. And they have a nice long taper 6 to 4 reducer.

View Redoak49's profile

Redoak49

5179 posts in 3042 days


#6 posted 02-01-2021 11:52 AM

I guess I went in a different direction. For me, it e seems like a real pain to seal the metal duct. I used 6” DWV which is not heavy and joints seal very well.

I have a 5 hp cyclone and ran 6” pipe and have very good flow and suction.

View controlfreak's profile

controlfreak

1967 posts in 655 days


#7 posted 02-01-2021 01:42 PM



I guess I went in a different direction. For me, it e seems like a real pain to seal the metal duct. I used 6” DWV which is not heavy and joints seal very well.

I have a 5 hp cyclone and ran 6” pipe and have very good flow and suction.

- Redoak49


Help me out here what is DWV?

View CharlesA's profile

CharlesA

3462 posts in 2851 days


#8 posted 02-01-2021 01:45 PM

DWV is Drain, Waste, and Vent. That’s what I used for my 4” duct. It is much lighter than schedule 40 since it is not made to handle pressuized water. In 6” it is not overly heavy, but much heavier than metal duct.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View BigMig's profile

BigMig

605 posts in 3667 days


#9 posted 02-01-2021 04:17 PM

Did you lose suction at the tools when you went from 4” to 6” ?

-- Mike from Lansdowne, PA

View splintergroup's profile

splintergroup

4973 posts in 2276 days


#10 posted 02-01-2021 05:27 PM

I have a 2HP cyclone and went with 6” SDR for the straight, ceiling mount drop trunk (about 15’ long) and used some of the PVC “Y’s” for branches. You are correct about the $$, but I like the ability to dry assemble and get tight joints.

The rest of the system is 6” Borg HVAC duct (the stuff with the lengthwise seam). Nice and light weight but does require the obligatory miles of foil tape. The bends are all done with the adjustable swivel “elbows” since I have some compound angles needed for routing. Nary any signs of collapsing when I slam shut the last blast gate even though the HVAC duct is thin.

View Kudzupatch's profile

Kudzupatch

172 posts in 2262 days


#11 posted 02-01-2021 05:33 PM



Did you lose suction at the tools when you went from 4” to 6” ?

- BigMig

As long as you have a big enough blower you will gain air flow/cfm/volume of air through the pipe. The volume of air you can move is what matters, not suction. More air flow pulls more dust in with it.

Yes, there is more involved but that is generally speaking.

-- Jeff Horton * Kudzu Craft skin boats* www.kudzucraft.com

View CharlesA's profile

CharlesA

3462 posts in 2851 days


#12 posted 02-01-2021 05:57 PM



Would you post a few pictures? I m particularly interested in your Y-joints and the main connection to your dust collector.

- menuisierJC

Here’s a pic of a wye that is on the ceiling branching off to 4” pvc drop.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View Holbs's profile

Holbs

2378 posts in 3083 days


#13 posted 02-01-2021 06:10 PM

I originally had 6” spiral duct and split duct HVAC 26gauge metal piping. My recommendation for anyone going down this path….contact your local HVAC distributor, if you have one in your local area. Just about same price tag of BORG stores but with the lower gauge. So win-win.
I ditched all my metal ducting and went 6” S&D plastic. Got tired of the paper cuts :) And not being a HVAC professional, my crimps & joints ended up being in the 4.5”-5” circumference on certain connections (especially, Y’s).
I went all S&D because can mold, bend, custom fit with heat gun for that super tight friction fit.
Total 6” footage would be around….60’ and then transition to some 20’ 4” pipe.

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter "xylokopos/ξυλοκὀπος"

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