SpudFiles

Hi, I recently built a PVC pneumatic potato gun but I'm having problems with leaking seams. I've tried pvc cement, guerilla glue, and black electric tape and was able to seal up most of the leaking seams but the gun still leaks air. Does anyone have any suggestions what else I could do to seal up the seams?

What material are you using? PVC? If you are, when you solvent welded it together, providing you primed, glued and twisted it, it should not be leaking?

But when all else fails. Epoxy

what i can recommend, is take some kind of tube that fits snugly over the pipe, and glue the tube over the leak. works wonders on my cannons.

Use a vacuum to pull epoxy, adhesive or solvent into the leaks. A layer of adhesive on top is not suitable.

inonickname wrote:Use a vacuum to pull epoxy, adhesive or solvent into the leaks. A layer of adhesive on top is not suitable.

yep do what he said put some epoxy on ur leaks and use a vacuum inside ur chamber to suck the epoxy into the leaks that should work nicely

Wow, that is a great example of parroting.

Oh like everyone knows how to create a vacuum..., alright mate, best thing is to smear epoxy over cracks and holes and then block one side of the air tank off while using a vacume cleaner to create a vacume leave it on, until you see a little epoxy on the inside of the crack, apply more if needed until the crack is filled. Remember to do all the cracks at once, or to let epoxy cure in between.

Edited for better manner of vacuum creation.

@John... I wouldn't advise that, inhaling the fumes from any glue is not the best idea. Nor, for that matter, is lung pressure likely to be enough.

irisher wrote:Wow, that is a great example of parroting.

Yes that is a great example of parroting!



Sorry couldn't resist.


Now for something informative: a vacuum cleaner will work, but for some real vacuum you could try a fridge compressor. Don't use your mouth.

I'm of the opinion that if it leaks that badly, the solvent welding job should be redone. Properly done, solvent welding should be leak free, by virtue of the way the process works - the pipe and fittings are chemically dissolved, pushed together with a tight tolerance, and then the plastic reforms as the solvent seeps out and evaporates.
If it leaks in several places, you have the symptom of a serious problem with the way the bond formed, or the shape of the fittings/pipe.

You can build a custom vacuum pump and use it to reduce the pressure in the chamber, allowing you to suck liquid epoxy or similar in through the gaps. A preferable method would be cutting it apart, getting new fittings, and trying it again. This will almost certainly be safer in the long run.

Ahh, the almighty fridge compressor... yes... i think that would work...
MAN!!!! i cant wait to get my new one all set up!

Anyways....gorilla glue= brittle... and porous
tape=NEVER A GOOD IDEA.

if the leak in in a threaded fitting... you should use more teflon tape.... and make the fittings tighter

if the leak is in a solvent welded part.... i would salvage what you can, learn from your mistakes... and try again.

PVC is cheap. cheaper than a good epoxy.... and if air is getting out somewhere.... there is a chance that your solvent weld job sucks..... and nobody wants your weld to fail... sending a 2'' endcap into your drywall 20 feet away...(personal experience.... ALWAYS SOLVENT WELD PROPERLY!!!!)

Good luck!

DYI wrote:I'm of the opinion that if it leaks that badly, the solvent welding job should be redone. Properly done, solvent welding should be leak free, by virtue of the way the process works - the pipe and fittings are chemically dissolved, pushed together with a tight tolerance, and then the plastic reforms as the solvent seeps out and evaporates.
If it leaks in several places, you have the symptom of a serious problem with the way the bond formed, or the shape of the fittings/pipe.

I had an early cannon with this problem. It was caused by leaving the saw cut rough on the end of the pipe. When it was inserted into the fitting, a burr on the end scraped the glue and some softened plastic pipe leaving a groove. The groove was very difficult to seal with solvent glue as it shrinks as it dries, which re opens the groove as the glue dries.

It is best to assemble the glue joints properly in the first place. Fixing leaks afterwards is often an exercise in futility..

Thanks for the input guys. I'm pretty sure that my problem is that my solvent weld sucks. This is unfortunate because I have about $70-$80 invested in pvc. Oh well, this was my first build and I guess I'll just have to try again.

Something many people forget when solvent welding:
90* twist after inserting the pieces
Very important. Don't do this and it leaks. Do this and it won't.