advice on DC piping size

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Forum topic by JesseTutt posted 10-16-2012 06:13 PM 1042 views 0 times favorited 11 replies Add to Favorites Watch
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854 posts in 2109 days

10-16-2012 06:13 PM

Topic tags/keywords: question dust collection

I am upgrading my 1 HP Penn State DC to a 2 HP Harbor Freight. I would like some practical advice on whether I should use 4” PVC tubing and fittings that I already have or upgrade the long run to 5”.

I plan to have two “runs” of flexible hose. One will be by the DC. The other will be in the middle of the shop where there is a 4’ decrease in shop width.

The 15 foot long “run” is what I need to size. It will be running along the wall between 10 and 12 inches above the floor. I plan to slope the run so that it is slightly lower at the DC end. Hopefully this will assist in pulling larger shavings down to the DC.

The DC will connect to a “Y” fitting using a short piece of either 4” or 5” flexible hose. Then “Y” fitting will have a 4” metal blast gate that connects to the flex hose.

At the far end there will be another “Y” fitting with the end caped (future expansion). Again there will be a 4” metal blast gate that connects to another piece of flex hose.

I already have everything to implement the solution using 4” PVC. The question is would I gain sufficient suction or CFM to justify the cost of purchasing 5” tubing, 5” “Y”s, and 5” to 4” reducers.

How would you advice?

-- Jesse, Saint Louis, Missouri

11 replies so far

View Grandpa's profile


3259 posts in 2674 days

#1 posted 10-16-2012 07:09 PM

Well, the 4” pipe would have a little over 12 sq. in. of area and the 5” pipe would have a little over 19 sq. in. That is 50% larger. I think you would realize a difference. Now is it worth the cost when you have a 2 HP collector (any brand). I don’t know. There are some others that have done this professionally. That is good but they often use HUGE systems. Try personal mail to Crank49. I think he has a lot of experience with this.

View Fred Hargis's profile

Fred Hargis

4986 posts in 2492 days

#2 posted 10-16-2012 07:32 PM

Try just using what you have . If it’s meets your needs you don;t have to do anything. If you need more performance, the upgrade may help. What I’m wondering is whether that DC will support a 5” duct. There needs to be a minimal amount of air moving, and feeding your 5” run (I think) is 4”, and some flex. You may not get enough air to keep the chips suspended (lots of clogs). So try what you have and go from there.

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

View crank49's profile


4030 posts in 2970 days

#3 posted 10-16-2012 07:55 PM

For me, it depends on what dust source is at the end of the long run.

Sanding dust, band saw dust, even table saw dust will usually not bridge up on a long run.

Planer, jointer, or router chips are another matter. These sources need plenty of flow and pressure.

A reasonable alternative is to put a drop-out box, Thein seperator, or similar device at the source, before the long pipe. Then the chunks and chips never get into the pipe in the first place.

As far as 5” vs 4” is concerned, ideal would be one long 5” pipe with no restriction to less than 5” before the fan. 5” pipe is hard to find and expensive.

I use 4” and 2-1/2” on mine.The 5” fan inlet on the 2hp HF collector has a “wye” fitting with two 4” connections. I run a 4” pipe from one side to the TS and can switch it over to the jointer if needded.
Then I reduced the other side of the “wye” to 2-1/2” and connect that to my band saw, or switch it over to the disk or belt sander. The 2 hp collector will handle one machine connected and operating on each of these connections, one 4” and one 2-1/2”, with no problem.

You may notice I didn’t mention my planer in relation to this setup. that’s because the planer is out in the garage, separate from the rest of my shop, and I just set it outside and let the chips fly when using it. Some day I will have everything in the shop together at which point I will probably put a dust deputy, or similar device on the planer before connection to the pipe. My planer only has a 2-1/2” connector so the bulky stuff will need to be dropped out of the air stream before going to a small pipe.

View HorizontalMike's profile


7757 posts in 2913 days

#4 posted 10-16-2012 08:08 PM

I would stick with the 4” duct, unless you upgrade to a Wynn filter on the DC unit. That will lower back pressure and move more air, making it more conducive for 5” piping.

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

View JesseTutt's profile


854 posts in 2109 days

#5 posted 10-16-2012 08:29 PM

I used a “water level” to measure the suction. With the old system I measured 2 1/8” change from level. With the new system I measured 3 5/8” change from level. To get either measurement I stuck the end of the clear plastic tube into the end of my 20’ flex hose that was directly hooked to the DC and then covered the remaining flex hose end with my hands. Without the hands covering the end there was very little change.

Is this a valid method of measuring suction?

Here is a picture of the setup (sorry it is rotated. You can barely make out the marks on the plywood):

-- Jesse, Saint Louis, Missouri

View Bill White's profile

Bill White

4930 posts in 3959 days

#6 posted 10-16-2012 08:32 PM

Though I have the HF DC, and I’m pleased with it, don’t believe the 2 hp rating.


View Cole Tallerman's profile

Cole Tallerman

392 posts in 2184 days

#7 posted 10-16-2012 10:57 PM

I have that dc and although i have 4” ducting, 5” would make a big difference. Mine is only hooked up to three machines and it works totally fine on 2 tools at a time. also, metal ducting from HD or Lowes is cheaper and looks better. just fyi.

View Fred Hargis's profile

Fred Hargis

4986 posts in 2492 days

#8 posted 10-17-2012 12:30 PM

You have simply made a manometer, and is one way of doing it. The key would be to watch for changes from some baseline that you establish. One other thing to keep in mind is that you can move too much air, that may result in overloading the motor. Check that with an amp meter. I put a Magnehelic on the discharge side of DC to track filter build up. It does basically the same thing as you manometer, but is an analog gauge. (BTW, these are fairly cheap on e-bay, not a big investment).

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

View derosa's profile


1577 posts in 2834 days

#9 posted 10-17-2012 12:53 PM

There will be improvement but it may not be worth the cost difference. The bigger issue may be the suction loss over 15’ of flex hose which can drop the amount of pull a lot. If you can shorten that to 10 it would make a big difference as well. Changing to a pleated filter from stock could make as much difference as switching to the five foot pipe may do and that could be the better initial investment.

-- --Rev. Russ in NY-- A posse ad esse

View JesseTutt's profile


854 posts in 2109 days

#10 posted 10-17-2012 02:09 PM

thanks for the information.

I do plan as funds permit to upgrade to the Wyn nano filter.

I think that I will stay with the 4” pvc for the moment.

-- Jesse, Saint Louis, Missouri

View Grandpa's profile


3259 posts in 2674 days

#11 posted 10-17-2012 03:19 PM

You have the 4” pipe so the only expense there will be your labor and caulk and tape. I am using 6” on my 5 hp collector. That will be the trunk line anyway. It cost me $36 for a 10’ joint. I bought 3 of those. Maybe that is expensive but it wasn’t too bad. The fittings are a different story. The pipe I bought was spiral wrap. The fittings are a little lighter duty (thinner material). I got many of the larger fittings at the local heat and air supply house. I was actually able to get a few of the fittings cheaper at my local ACE hardware store and they were reasonably priced there.

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