Glue PVC ductwork

[Bernie Kopfer]

I am ready to install 6" pvc ducting for my shop connected to a 3hp collector. Although I know what I want for now and where my machinery sits, I also know that my shop is an evolving thing and placement might change. I've read somewhere before that pvc does not need to be glued together. Is this true?
By the way I will use flex tubing to connect to the machinery. Thanks

[Myk Rian]

I don't glue it. Instead, I use 2 screws on the joints, and wrap a cloth tape around them for a seal. Duct tape will also work. Glad I do it that way. I just re-arranged the whole system the last 2 days. Finishing it up today.

I've been helping a friend install his Oneida system. They recommend using silicone on the joints, AFTER you get them together. Just a thin bead.

[Stephen Edwards]

I don't glue it either. It's not necessary. If you decide to move things around later on it's going to be much less expensive to do.

I like to use a premium grade of duct tape. In a few places I'll add a screw or two. Most of the joints it's just duct tape. Works fine with no problems.

[Tony Shea]

I def wouldn't use PVC glue as there is no turning back, I'm an electrician and install underground services with it. But I do like the idea of just dry fitting them together and place a bead of silicon around the lip to keep the peice in place. Just cut the seam with a knife and they should pull apart easily. Never thought of the silicon idea. It would also create a cleaner look than wraping duct tape around each joint.

[John Coloccia]

Definately don't use glue

I drive 2 or 3 sheet metal screw through the joints to keep them from twisting apart. I don't seal the joints with duct tape anymore. I did the first time around, but found it made absolutely no difference.

[Alan Schaffter]

• DON'T use glue

• Dry, friction fit is fine in most cases.

• Use a small screw or two on vertical runs if necessary to keep pipe from slipping out.

• DON'T use duct tape- it doesn't last and the adhesive degrades quickly leaving a hard-to-remove, crusty, nasty residue. If you want to use tape, use foil-faced tape - the "real" duct tape.

• Apply a very small bead of 100% silicone caulk to the OUTSIDE of the joint, after it is together if you want to ensure a perfect seal- remember, the system is under suction so the pressure will hold the silicone against the joint.

• DON'T use latex, siliconized latex, or other caulks. 100% silicone caulk can be rubbed off PVC and metal duct very easily with just your fingers when it is time to reconfigure your ductwork- other caulks are MUCH HARDER to remove.

p.s. if you are OCD or just want a very neat looking sealed joint- before you apply the silicone, wrap painters tape around the pipe straddling the joint so there is a small 1/8" or 1/4" gap. Apply the silicone, smooth it into the joint with a wetted finger, then remove the tape. Result- perfect looking and performing seal.

[Jim O'Dell]

+100 on not gluing the joints. I didn't use any screws either, as I didn't want anything protruding into the air path to catch strands of wood. On one 4" joint that was very loose, I did put in 3 or 4 rivets...from the inside so it was smooth. I did caulk the seams after installed. And yes, the siliconized caulk is tougher to get off. Didn't realize the 100% silicone was easier. I'll get some of that for my redo I'm in the middle of! Jim.

[Tim Cleary]

Hey Jim: how did you crawl inside the PVC to install the rivets from the inside

[Jim O'Dell]

Luckily it was at a 6-6-4 wye, and I was putting on a short piece of straight pipe to go to flex hose, so I was able to go in the pipe side. It was tight with 4". Would be easy with 6". But no, the length of your arm is the furthest you could do a joint. Jim.

[Dave Cav]

If I KNOW I'll never take the joint apart (like a straight run) I might use PVC glue. (And I've STILL had to take a few apart with a saw.) Mostly now I use hot glue to seal the joints; they are airtight but still can be taken apart (with a little effort). And hot glue is cheap.

[Myk Rian]

According to Oneida, screws poking through the walls of ducting will not create flow problems, nor catch material going through.

[Bernie Kopfer]

Thank you all for the helpful responses. Forums like this where we help each other make this world a better place.

[glenn bradley]

I have no glue in any of my joints. The slip fit of the ASTM-2729 I used is tight with about a 1/4 twist just as if you were gluing them. Been up for over a year with plenty of blast gate opening and closing-type tugging and bumping going on. I have also opened off sections to add wyes and such just as you describe the changes that may take place in your system. No worries. I do have the runs hung from overhead with plumber's tape and strapped to the wall with same.

[Steve Peterson]

One more point that was not mentioned is that the fittings are extremely expensive. If (or when) you want to change the ducting, you will have to throw away the old fittings if they are glued.

You could conceivably use 3 straight couplings to reuse a tee that has been glued, but straight 6" couplings are around $8 each, so there is no savings.

Steve

[paul cottingham]

I just finished replacing the run to my jointer with 4"pvc. It has a couple of elbows and two fittings to join it to flex hose. I initially set it up with no glue or screws just for initial fitting. It works so well, and has so little leakage that I am just going to leave it.

Will make "moves, adds, and changes" much easier.