Flex tube - okay, I've learned my lesson

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Forum topic by Woodtechie posted 01-16-2015 06:12 AM 1513 views 0 times favorited 18 replies Add to Favorites Watch
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55 posts in 1594 days

01-16-2015 06:12 AM

I hate flex tube – can’t stand the crap. It worked for awhile to get me by without spending too much, but I just made the mistake of not procrastinating, and finally started re-arranging stuff to make some kind of sense (no more tubes on the floor). Now I feel like I never should have disconnected the stuff—such a pain to work with! I forgot how terrible this stuff is to re-connect.

I wasn’t planning on spending more for this so soon, but I’m not sure I can do it correctly with this junk. I knew it was far from ideal from the beginning but.. budget.

Trying to decide if I should just try to tough it out and make it work, or invest in pvc or metal ducts. I’m working with 4” “Woodstock” garbage plastic tube and just plain 4” metal band clamps which don’t really do a very good job holding things in place.

I have a 20×22 garage shop with just a 2HP Grizzly dc, but I think I can keep the ducts somewhat short. A 2nd dc for the other side of the room could be in the budget long term. (Still need to fit a router table in somewhere and a drum sander is on my long term wish list.)

The sander and mitre saw are not connected to the dc for now (sander really needs it but I don’t care about the mitre). The planer had a cheap quick-connect which shared a dc port with the table saw, both had tube just running on the floor. Jointer and bandsaw were connected with the other two blast gates at the dc (3 total). TS duct should hang from the ceiling but I’m not sure how well that’d work.

Willing to consider re-arranging layout if it helps. (And despite how it looks, unfortunately the table is too low to function as an outfeed table.)

What would it cost me in time and money if I go with pvc? Does anyone here even bother with plastic flex tube?

18 replies so far

View OSU55's profile (online now)


1625 posts in 1952 days

#1 posted 01-16-2015 12:46 PM

Yes, I use 1 piece of 4” flex 10 ft long, with the same DC. I hook up each machine (TS, planer, router) as needed. To permanently plumb lines in, use PVC sewer drain line which is thin walled and cheaper. 10 ft section is ~$8.50 at the local Lowe’s. The best would 6” lines ran to each machine to reduce pressure drop, but would be expensive, and the HF DC doesn’t produce enough flow to capture ALL the dust anyway, so 6” doesn’t really fix anything. For some reason 6” PVC sewer line is currently on sale at Lowe’s for $1.75/10 ft. There is enough dust escaping from the machine cut to be a hazard, so a respirator is still needed, especially when you get the drum sander. Layout looks fine, much less crowded than my shop, which is not dedicated to just woodworking.

View gtbuzz's profile


427 posts in 2404 days

#2 posted 01-16-2015 12:47 PM

Short runs of flex are okay for the final connection for the machine, but ignoring the pain of working with it, it’s not a good idea for your main runs because the corrugated interior walls cause a lot of turbulence for the airflow. That increases the static pressure and reduces the overall CFM you get at your tools.

Mainly due to cost, I didn’t go with PVC in my system, but rather 28ga hvac ducting. Reason I went with it is that it was much easier to work (much lighter) and much cheaper to buy as well. There’s debate over if you can get away with 30ga ducting as it seems prone to collapsing if you accidentally leave all the blast gates closed. My local HVAC supplier had 28ga for less than 30ga at the big box stores, so I just went with that, but I probably would have taken my chances with 30 had it not been available because there’s a pretty big price jump from 30 to 26 that you’ll find on places like PSI and Oneida.

As far as the flex hose, I don’t bother with standard band clamps, they’re junk. Rockler sells bridge clamps that I really like because they have a key on them to loosen / tighten which means I don’t have to reach for a screwdriver every time. They’re kind of expensive though, so for the permanent connections I just use regular band clamps, which you can get at an auto supply or industrial supply store (mine came from McMaster Carr).

PS – I like that shop diagram. What software did you use for that?

View brtech's profile


1028 posts in 2886 days

#3 posted 01-16-2015 02:54 PM

It’s a conundrum, and I have the same issue, and the same DC.

6” main is too big for that DC, 5” is too expensive, and 4” is too small for the main runs. Tying into the TS is a problem because the down pipe has to be far enough away from the saw to not interfere with big pieces going through it—which is effectively 8’ from the blade on the left, and the length of the extension table on the right, and, depending on how you handle sheet goods, 4-8’ front and back of the blade. Then you need to run the duct on the floor, which seems to usually be a trip hazard, and by the time you have gone up from the DC, across on the main, down on the down pipe and across to the TS,, up and across to the port, you have a very long run and 5-6 90 degree turns (which are either expensive wide sweep or two 45s and a short straight pipe).

I just made my situation a lot better, and it cost $100 and 15 minutes. The Rockler DustRight collapsable hose.
I got a 21’ extended, 3’ collapsed piece, starter kit (it was on sale), and a 2 pack of the 4” adapters.
It’s long enough to reach all my tools easily. And you can turn the DC on, block off the end with board, and it sucks itself back down to 3’ (or wherever you are standing). The only downside is that it’s pretty heavy. I tried to get out of using the handle and ports, but it just wasn’t the same as putting their ports on all my tools and using the handle. You can do it, it’s just no where near as convenient.

View dozer57's profile


92 posts in 1463 days

#4 posted 01-16-2015 03:58 PM

IMO I would run 4 inc pvc all the way, one run up the wall behind you dc and then around the shop just below the ceiling with drops a your tool stations with blast gates. For the ts run a drop from overhead. no stepping over your hoses this way. As far as a drum sander I have mine on 4 inch with a 40 foot run. work great as fine sanding dust pulls easy.

View mramseyISU's profile


533 posts in 1508 days

#5 posted 01-16-2015 04:13 PM

My shop isn’t as big as yours but the biggest issue I have is my stupid blast gates getting filled with crap in the corners causing them not to shut all the way. I read something in woodsmith or shop notes suggesting you snip the ends just enough that you can clean them out. That made a big difference for me even with running all the flex tube I’ve got.

-- Trust me I'm an engineer.

View Fred Hargis's profile

Fred Hargis

4949 posts in 2456 days

#6 posted 01-16-2015 05:49 PM

4” PVC can be had fairly cheap if that’s the size you want. The 6” gets more expensive, besides being a lot harder to find. The biggest cost with the 6” will be the fittings. It’s not hard to approximate what you might need for an estimate. A very rough sketch of how to want to lay the ducting out, and then you can count the el’s and y’s you need. A quick measurement for the straight runs, remembering you need to think in 3D instead of 2D. Then a trip to the store to get the individual costs. Blast gates are cheaper (and better) if you make your own, versus the plastic ones, and you will still need some small pieces of flex to hook to some of the machines.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Woodtechie's profile


55 posts in 1594 days

#7 posted 01-18-2015 01:56 AM

@gtbuzz Diagram was done with Sketchup (free version). Google has a 3d warehouse where you can find all those models right from the application’s File menu (except for the room dimensions).

I’m glad nobody is saying that I absolutely need 6” tubes, I was worried about that. The 4” is affordable but I know how these things can add up quick. I could do 6 inch if I take that 3-way splitter off (it’s kind of bulky) but all my machine ports are 4” or smaller anyway. I really want to minimize the amount of space wasted as much as possible.

View Tom Clark's profile

Tom Clark

88 posts in 2984 days

#8 posted 01-18-2015 01:15 PM

I have been using a simple set up with flex tube for around 25 years. Never a problem. Longest piece is 10’ to the table saw. Guess the crap works fine as long as runs are not too long. I kept the setup simple by keeping the machines that need dust collection all together.

-- Tom

View Picklehead's profile


1041 posts in 1892 days

#9 posted 01-18-2015 02:49 PM

Tom, looks like you captured the rare and elusive Octopotamus.

-- You've got to be smarter than the tree.

View Fred Hargis's profile

Fred Hargis

4949 posts in 2456 days

#10 posted 01-18-2015 02:58 PM

Woodtechie, I’m not pimping for 6” but just want to say: never,ever,ever be put off by the factory ports on machines. If they need upsizes to do whatever you want, then do so. Remember, good DC is about LOTS of air flow, that can only be done with adequate ducting/ports/whatever.

-- Our village hasn't lost it's idiot, he was elected to congress.

View verdesardog's profile


158 posts in 2574 days

#11 posted 01-18-2015 03:32 PM

Remember that just airflow is not the answer, a DC needs velocity to keep the particles in suspension. for a normal handyman size shop 4” is fine.

-- .. heyoka ..

View Woodtechie's profile


55 posts in 1594 days

#12 posted 01-18-2015 06:59 PM

Tom – the flex tube insults were more a result of my sore hands after messing with the stuff a little too long. For my short runs I’m pretty sure it’d be okay function wise as you say.

Someone here gave me similar advice about that kind of layout before, but I think I’m more stuck to the wall. The problem with having it in the center like that is power. Not that there isn’t enough- I went absolutely bonkers adding 220v (way overkill for future expansion and moving stuff around), but with all that I didn’t have the foresight to put any on the ceiling for drops down the center of the room. I’m probably a little too clumsy and fast walking to tolerate one of those floor cord covers. I’d still trip on it.

I’m not pro like some of you here so I’m sure I’ll be fine with 4”.

View JAAune's profile


1786 posts in 2280 days

#13 posted 01-18-2015 08:27 PM

4” will get most of the dust if setup correctly but unless the dust hoods for the machines are designed perfectly, it’ll still allow a fair bit of dust to escape. You’ll need to wear a dust mask during long machine sessions, clean up with a vacuum and filter or ventilate the shop air to avoid clogged sinuses.

That 2HP collector might not pull enough CFM for 6” duct though and they usually come with 5” entry points. Not much sense running 6” ducts if the airflow gets choked at the machine.

If you are near Chicago, Air Duct Mfg. has a good selection and reasonable prices. I’ve put a screenshot of my Sketchup drawing showing the pipe layout. That’s a decent amount of pipe and fittings and when all’s said and done, it’ll cost under $1,000 for the duct and fittings. That’s 116’ of mostly 7” and 6” spiral duct and die-stamped, long-radius elbows. Anyone would be hard pressed to beat that price even using inferior Lowes ducting.

The cost of running the same duct for the smaller setup that the OP has should be far less. I estimate around $300 which is probably comparable to the cost of PVC. All the cost is in the fittings. 6” spiral duct alone is less than $2 per lineal foot from the company I referenced. Someone on a really tight budget could buy the spiral pipe then use 30 gauge fittings from Lowes to finish the job.

One recommendation regarding the shop arrangement would be to move the dust collector into the corner where the bandsaw is. Put most of the tools requiring dust collection lined up along the same wall. Run a single 5” duct all the way down that wall and send a branch off that to go up and over to the table saw. All the tools will have a blast gate and a length of flex hose connecting them to the 5” main.

That arrangement will get everything hooked up with about 40 feet of pipe and no tool will have more than 20’ of duct between it and the collector.

-- See my work at and

View Woodtechie's profile


55 posts in 1594 days

#14 posted 01-19-2015 04:02 AM

That’s a nice diagram, it’s not common to find real examples of how people lay these things out. I was going to go around the walls, but seeing that makes me want to try diagonal. (Potential issue is the huge fluorescent lights up there the tube needs to duck under.)

The reason the DC is between the BS and Jointer is the direction of the dust ports – they’re all currently facing directly towards the DC in the original diagram, so there are no major bends.

This is a lot of work and a lot of pipe, but does anyone see any obvious problems with this? Any cool toys (large tools) I may want some day that I forgot about? This way I get to take advantage of that extra 2’ shop width I have on the electric subpanel side—I can tuck the DC partly behind the jointer. It’s remote controlled and the bag should still be accessible.

Added an imaginary drum sander and router table. I’m thinking of just a flex tube drop for the planer which rolls out when needed.

How far down should the actual PVC go from the ceiling (particularly for that center drop) before I have to switch to flex tube? This is turning into a big project isn’t it.

View JAAune's profile


1786 posts in 2280 days

#15 posted 01-19-2015 05:12 AM

Thanks. One thing you can’t see from the picture is that I’ve used dynamic components in Sketchup (feature in the pro version) that calculates the static pressure loss for each fitting and duct run. For my 3HP collector, I had to keep the SP loss under 6”WG to maintain proper CFM. The duct layout is designed to minimize SP loss without requiring an excessive number of branches that raise the cost.

The general rule is that you get as close as you can with rigid pipe and use just enough flex to make the connection easy. It’s a pain getting the duct perfectly aligned with the dust ports. In my case, the higher grade flex that I will eventually use is more expensive than duct so it pays to minimize the amount needed.

There are exceptions of course as in the case of mobile tools. Leave enough flex on the planer so you can move it as necessary. Just bring the duct down enough so you can reach the blast gate.

As far as running pipe diagonal like that, the biggest issue may be overhead clearance. I don’t know how tall your ceilings are. If duct is hanging less than 8’ above the floor, you may hit it while swinging long boards around. My shop has 14’ high ceilings and the duct is 10’ up.

There’s one other issue regarding the layout. That run going towards the planer has a drop going straight down to the table saw. When you use the planer, shavings might fall into it and clog up that line. Notice in my layout that all branches have some horizontal direction before they drop? That keeps them clean.

I would suggest trying the following if you want a diagonal main running across like that.

1. Run the main line directly to the spindle sander, have it drop down then insert a wye on the drop. The straight portion goes to the sander and the other one is for the planer.

2. Send a branch off the main a short distance to the table saw then drop down and run it under the saw within a couple feet of the dust port.

3. Send a branch and a drop to the location of the sander.

-- See my work at and

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