SpudFiles

Hi all,
my question is, i used primer and glue to create a pneumatic chamber, and when i pressure tested it, the seal between the fitting and the pipe sprung a leak, why? I followed all the directions given (what with the wet primer and quarter turns and all) and, is there anything i can do, short of re-doing it completely, to repair the leak from the outside.

i considered maybe drizzling super glue or even more pipe cement into the leak with negative pressure in the tank

Did you let the weld cure?
Check that it is PVC primer, PVC glue, and PVC pipe (if anything says ABS you used the wrong kind)
You could attempt to seal the leak, but it may just happen again, or other parts of the same seal may be bad.
Depending on where on the chamber the bad seal is, it may make more sense to just cut off that fitting and replace it. For example if it's an endcap, it would just be easier to redo it.

You must not have used enough primer and glue. When you press the fittings together, a little bit of glue should be visible. Also what some people like to do is use a padded mallet to tap the fittings together. They should be pressed together as far as possible.

This Solvent welding course can also help.

thanx for the quick replies guys, yes all parts were sch 40 pressure rated pvc, and i used purple primer and glue for pvc from a company called oatey. The parts in question were a 4 inch diameter pipe and a reducer fitting. Does the glue ever go bad, because it occurs to me that the can in question may in fact be over two years old.
thanks again guys

also, the parts fit together pretty tightly without glue and bottomed out when assembled with, yes thank you, lots of glue.

Some people have successfully used the technique you suggested in your original post - using low pressure in the tank to draw glue into it, although epoxy may be a better option.

As a note, leaks tend to indicate weak solvent welds, so be weary of failures.

i find that i have to go around about 5 times with primmer and get it really purple, then go around 5 or 6 times with glue. epoxy would work to seal it. if it leaks you either did it wrong or you pressurized it before it dryed.

on a previous cannon i tried some epoxy for a leak and couldn't get the epoxy to actually stick to the pvc, i re-read the directions and it was recomended for pvc, but like i said it just flaked off after a thorough cleaning, drying, and a 24 hour dry\cure time. thanx but it looks like i'll just have to call a mulligan on this one

I think your cement may just be old. I had the same problem recently. If the cement is REALLY old, it might even be solid. (This happened to me once.) Heck, I bought some cement once, used it a few times, and only two or so months later, it was jelly-ish goo. Needless to say, I was pissed!

Pilgrimman wrote:I think your cement may just be old. I had the same problem recently. If the cement is REALLY old, it might even be solid. (This happened to me once.) Heck, I bought some cement once, used it a few times, and only two or so months later, it was jelly-ish goo. Needless to say, I was pissed!

That also happens when you leave them somewhat open. I have a tendancy to do that. So I've got like 5 half full, solidified jars of glue sitting on my workbench. The happen to fit in a 2" barrel pretty snugly, so they work as ammo now.

The happen to fit in a 2" barrel pretty snugly, so they work as ammo now.

OMG! That's my next gun! *Runs off to build it*

The glue goes bad if you let it get too cold. I stored a couple bottles in my house for a while, they were fine. After it was in the garage when it was freezing out though, it turned into jelly. I had that happen both with some like 3 year old stuff, and some stuff I just bought a couple months prior.

I use heavy duty glue, and clear primer. I get the pipe and fitting good and primed. May brush the primer on for a minute or so until I see a little white coming off onto the brush. Then glue, a generous amount. I haven't had a single problem. Of course, my joints ooze a decent bit and I let it dry so the wet part is up. I'm not super eager to get things done since I can't shoot them where I live, so I may glue a guy together over the course of a few days and it may cure at least a few before getting to fire it.

quick update: super glue, vaccum, superglue gel. no problem. tested to 150psi no leaks, works like a dream, pics coming soon. thanx again to every body who responded 8)