Compressed Air Leaks

jedens · Nov 12, 2002

Thanks to everyone for all the suggestions. I'm going to the hardware store later today and get some pipe dope and Locktite. I'll let you know how it holds.

kyoders · Nov 15, 2002

Stainless is harder to seal than brass/galvanized steel? That's a relief, I thought it was just me. I just put in an auxillary water line for irrigation and ended up using stainless for the above-ground portion (couldn't find brass locally, SS was almost as cheap mail order). I had a bear of a time getting it sealed with tape. I ended up going back with Rectorseal on most of it, and that seemed to do a lot better. I think I may re-do the remaining part, just for grins. I need to take the above-ground part in for the winter anyway.

Is this due to the fractured-looking appearance of the threads? I was surprised to see this on my (high-dollar) fittings, but it sounds like it may be the nature of the material? Anyway, thanks for the good info.

Kevin

em14 · Nov 15, 2002

Why did you use Stainless Steel or Brass for an irrigation system ... this must be high pressure ...

chim · Nov 16, 2002

Threads are more difficult to cut cleanly on stainless, and I think the hardness of the stainless limits just how much it will deform to seal theads. I also galls sometimes if you try to "dry fit" pieces together. On applications where it's acceptable, our guys prefer to weld stainless rather than thread it.............chim

kyoders · Nov 20, 2002

I needed to use an RP backflow device so I could inject fertilizer. The RP has to be installed above ground. Any pipe under continuous pressure that is less than 18" deep needs to be metal. Also, standard PVC is not UV resistant, so having it exposed is not good. I thought about using galvanized steel, but I've seen places where it's rotted through (well, oxidized I suppose) in a remarkably short time. We have extremely acidic soil, so I figured it would probably go even faster. Thus, I wanted to use brass. It turned out getting stainless was a lot easier and just as cheap. So, after the long way around the barn, that's why the stainless. It only goes from the tee in my main water line to where the downstream side of the RP goes back to 18", then it's PVC from there.

I wish it was due to high pressure. My well only recovers at 12GPM, and the dynamic pressure I'm left to work with is only 31PSI, so I'm marginal at the sprinkler heads, and I have to use a lot more zones than I would like. Oh well, my neighbor only makes 1GPM on her well, so I guess it could be worse (the neighbor on the other side makes 30+).

Kevin

em14 · Nov 21, 2002

Thanks .. I’m on a well also and for the system that I have here in Florida I have the antisphon valves above ground and used schedule 40 PVC through out … I have a back flow preventer valve underground before all of this and after the house water so that nothing gets in the house water … maybe a little much but I feel better … I did cover the valves and the exposed PVC with a small structure made of PT plywood that looks some thing like a box and I think it will be fine … I didn’t realize PVC had that big of a problem with UV … I covered it up to hide the pipes and valves ….

kyoders · Nov 21, 2002

I should have added that you need to check your local code requirements. My parents' system in Florida is very similar to yours, but it wouldn't do as well here with ground freeze. The RP device has unions on each side so that it can be brought in for the winter.

I've been told that the grey sched 80 PVC has been treated for UV, but I would be leery of that. That was at Lowe's/Home Depot, and I think half the people that work there will answer any question, whether they have a clue or not. If you have PVC exposed, you should at least paint it, preferably something reflective. If you leave it exposed to UV, it will eventually fail. Your PT covers are probably as good/better than painting.

Kevin

fractal · Jan 27, 2003

jedens

I realize this thread has gone various directions since you first posted but thought I might respond to your initial problem. First of all, I have one fo the harbor freight 40 pound sand blasters my self. It leaks like a sieve. I don't mind cause I go through air at an alarming rate. I get a 20% duty cycle with a sears "5 hp" compressor. I might get 25% if I fixed all the leaks.

Pipe dope, sold at home depot and all hardware stores, is INFINATELY better than teflon tape. Cheaper, easier to use and works much better, or so I have been told. I used the tape that came with mine and mine leaks like a sieve.

Basic pipe dope is good for way more than the 100 PSI you are gonna put into our sand blaster. I would go with it if you really want to get rid of your leaks. Otherwise, just realize that as soon as you open your nozel that you are going through tens of cfm of air so leaks are insignificant..