Metal Duct to PVC Transition Question

[Mark Duksta]

Hello All,

I just got my ductwork plan from Oneida. Ouch! $1300. I'm going to need to cut some corners. So where the plan calls for a reduction from 7" to 6" pipe I'm going to run 6" S&D. How difficult is that transition going to be? I saw a rubber coupler at the borg. Would I need something like that?

Mark D.

[Bill Erskine]

Mark,

I feel your pain. (I was quoted ~ $1,500 for my ducts, so I was mightly pleased to pay $450 for my S&D PVC.) I'm literally in the middle of installing 6" S&D in my shop. My Onieda cyclone has the 7" inlet. What I found, and sounds like you did too, is a 6" pvc/steel to 6" clay pipe coupler. It was perfect (fit wise) for connecting the S&D to the cyclone inlet. Maybe not the most perfect for airflow reasons, but I plan to address that if/when I need to.

[Jim Becker]

Mark, measure a normal metal 7" to 6" long reducer to see if it will work for you.

[Ken Garlock]

Hi Mark. You can get reducing couplings at Air Handling Systems (http://www.airhand.com/product.asp?CategoryID=7&SubCategoryID=0) These are high quality machined pieces, and will run you in the 20 to 25 dollar range. Expensive, well yes compared to the "tin foil" parts you get at the borg.

At least give them a look :)

[JayStPeter]

I figured out a way to transition from 6" metal to 6" PVC pretty much seamlessly. What I did was wrap the 6" metal duct end with some window/door sealing foam (I believe 3/16" thick), then shoved it into the wide PVC coupler. It fits nice and tight, then just a little foil tape and it's a solid connection. At the end of the coupling, the interior metal and PVC meet with a minimal seam.
To get from 7" to 6", I used a metal adapter or 7x6x6 wye. There was also a place where I needed to use 6" metal adjustable angles to get around an odd corner. Same process.
BTW, the borg has some of the metal fittings. It is thinner than the Oneida stuff, but the fittings usually have some sort of rolled section that makes them quite strong. I got at least one 7x6 adapter and some 6" adjustable 90* there. Since they don't sell long radius 90s, I just used two and set them each for @45*. Still winds up less than half the price of one from Oneida. I used the straight stuff from Oneida as the stuff from the borg is just too wimpy.

Jay

[Jim Andrew]

I've been shopping for 6"S&D, can only find SER 35 at the local Lowe's. It
runs about 2$ per foot, the 6" Y is over 12$ to fit that pipe. Is that what
you have encountered? Jim

[Mark Duksta]

Jim,

I have found a supplier of 6" S&D pipe locally. I'll be dropping by there this afternoon. I'll let you know what the prices are like. Online I've found prices for 2729 S&D fittings comparable to what you are finding. $12 bucks for a wye is still about a third of the cost of a metal wye fitting.

Mark

[Steve Cox]

When I was faced with mating my PVC pipe to the inlet on my Woodsucker I finally wound up using my laminate trimmer and a made up rabbeting bit to thin down the PVC until it slid on to the inlet and then I used a hose clamp. I made the bit by swapping bearings on a flush trim bit until I had a setup that would cut a 1/16" rabbet.

[JayStPeter]

I've been shopping for 6"S&D, can only find SER 35 at the local Lowe's. It
runs about 2$ per foot, the 6" Y is over 12$ to fit that pipe. Is that what
you have encountered? Jim

Those are about the prices I paid. You don't save anything on the straight runs over metal. But, as mentioned, the $12 wye is around $40 in metal.

Overall, I saved a lot of money over the Oneida quote. My quote was over $1600 and included some mistakes that would add some more money. I think I'm sitting at around $750 right now with PVC and homemade blast gates. But, I do still have another $100-$150 or so to spend to get it close to the configuration that was quoted. I have a temporary hack in for the miter saw and am currently sharing a connection between the jointer and router table as I didn't order enough flex tubing. I also used some Shop Vac hoses for smaller connections (Miter saw and BOSS) that I want to replace with the nicer Oneida tubing that will be a little more flexible. Most of my added cost will be new tubing from Oneida (2.5 or 3", 4" and 6"). But, I will be adding one more drop to the system that I estimate will cost around $25 as I have some leftover 6" pipe and will make my own blast gate. I need a wye, a 45, and a melamine shelf to make the gate out of.

Jay

[Michael Perata]

Mark

I found the 6" metal fittings from Oneida fit snuggly into 6" PVC S&D pipe. I pay about $12/10' locally for the S&D pipe.

[JayStPeter]

Mark

I found the 6" metal fittings from Oneida fit snuggly into 6" PVC S&D pipe. I pay about $12/10' locally for the S&D pipe.

The 6" metal fittings and pipe I got from Oneida had the exact same ID as PVC. The crimped ends do fit in, but I didn't want crimped ends (or even lips) that would be backward to the airflow. Since I used metal for the first 3-5 feet from the cyclone, pretty much all my metal to PVC transitions were backward for shoving metal into PVC. The way I wound up doing it (or the rabbeting bit way) yield very smooth inner transitions. There are some places I crimped metal to ease machine hookups that were in the proper direction.

Jay

[Mark Duksta]

Thanks for the tips. I just palced an order with Oneida for some 7" diameter pipe and fixtures. I'm going to go a few feet with 7" then reduce down to 6. They said it would be 5 to 7 working days before it ships. I had to wait three weeks for the ducting plan. All this waiting is frustrating. In the mean time I'm going to get started with building the blast gates.

Mark

[Bill Lewis]

Mark,

My quote from Oneida was also on the order of about $1300. So far I have expanded my system from the original design, and I have "only" spent about $700 total. I used their plan as a guide, but remained flexible enough to change it along the way, making it more efficient, and more cost effective.

I just got my (hopefully) last order from them last night. At this point I don't think I'll need to order anything else from them. I eliminated things from the Oneida quote like the blast gate adapters, and hose clamps.

I think placing the quoted order outright would have been foolish. I'm sure I would have wound up with too many leftover things if I had done that. While placing several orders may take a bit longer, It works out better in the end.

I should have my system completed enough to start planing some wood this weekend. :D

[Mark Duksta]

Bill,

Congradulations on completing your DC project. This is taking longer than I expected. It's not taking me long to figure out what I need. It's Oneida I've had to wait on. Ten days to get the cyclone, 21 days to get the plan, now 5 to 7 days to get the parts out their door. The plan I got from them will be a rough guide to my system. There were more than a few mistakes. Aside from the waiting, they have been a good company to deal with.

Mark

[Chris Padilla]

Check your local irrigation houses. We have a nice big one here in San Jose (Horizon). The straight pipe is cheap but the fittings are better purchased from McMaster-Carr.

[Paul Thompson]

I can't be the only one wondering what S&D stands for.... :)

[Mark Duksta]

Sewer and Drain

[Don Martindale]

Not to be a wet blanket, but before anybody spends a lot of money on a PVC DC duct system, you may want to check with your local building dept. Many fire marshalls prohibit the use of PVC for ANY ducting, due to its chemical reaction & fumes emitted when exposed to extreme heat. I have always used steel for this type of system, but to be honest, other than mine, it was for commercial use....don

[Ed Weiser]

PVC versus metal ducting for dust collection has been debated and researched quite thoroughly (I think.) The bottom line is that for most jurisdictions in hobby (non-commercial) shops with DC 3 hp or less PVC seems to pose little risk. The issue of heat and fire for woodworking-type dust is minor (except in the DC bin or bags which need to be emptied regularly (read DAILY) and I'm not sure fumes would be an issue either (?). Static shock does occurs but for non-production shops again is minor. Explosions in this setting seem to fall in the realm of urban legend (everybody talks about it but no one has actually confirmed such an explosion.)

Check out Bill Pentz's site for info about PVC ducting:
http://billpentz.com/woodworking/cyclone/index.cfm

As far an adapter is concerned, I also used the hard rubber PVC to clay pipe adapter and it fit the 7" intake of my 2 hp commercial Oneida DC without problems or much apparent effect on efficiency. The presence of at least 24" of straight run leading into the DC seems to be more crucial.

Hope this helps.

[Don Martindale]

My post was only to let people know about possible fire code violations using PVC as a duct. In several shoreline towns in Ct, fire code states that PVC shall not be used as a duct or plenum media. I believe that this may include the reasons listed above, along with the fact that it can act as a fire chase if installed in such a way. I don't make the codes, but I'm forced to follow them. A few years ago there was a lot of info about pro's & con's using plastic pipe as an airflow medium. My personal opinion is that I can size, fab, & install a system from steel, & tailor it to fit an exact situation quicker, & less costly than using plastic pipe. It would also stink to have an inspector in your home, & make you rip it out because you failed to check local codes.....don