SpudFiles

We have done some more tests in the last few minutes and the cannon only seems to work at at very low pressure and is still hoonking.

Also we tried removing the air nozzle but it didnt seem to make any noticable difference...

DWV stands for Drain Waste Vent while PW means Potable Water, according to DYI.

Seems as though I've become something of a plumbing expert...
PW stands for potable water. Since all drinking water delivery systems must be pressurised by nature, PW is pressure rated.

As for sprinkler valves, I don't have any practical experience with them, but it seems like the problem could be either: small vent diameter (safety tip on blowgun)
Small valve
Low pressure
Or a combination of more than one of these, assuming that everything else is done properly.

Try opening up the valve, and checking the diaphragm. On mine there was a screw hole on the pistony part, that went all of the way through. I filled that up with goop and my air leaking was fixed. I never had a honking problem though, so I dont know if this will help.

Do they sell caps that are PW rated and threaded? That is what we need so we can fit multiple styles of fill valves to the expansion/storage chamber.

Its called a threaded plug.

The reason that valves honk is the diaphram is bounding up and down on the seat inside the valve. Basically there is not enough air flowing to keep the diaphram open, (the spring is stronger than the flow of air). You mention that you are only running at low pressures currently and that is what is causing it. Upping the pressure to above 40 should significantly reduce the honk, however, you are also greatly increasing the chance of winning a Darwin award.

People will tell you that DWV is safe up to like 70 PSI. DWV is not safe, at any pressure. When it fails, it will not give any warning, it will just blow up. Your particular parts might be able to hold 400 psi, or 45 psi. Since they are not rated, they are not tested, so no one knows. DWV is not held to the manufacturing standards that PW is held to. PW still has minute flaws that can cause failure. DWV is much more likely to have them. DWV only needs to be able to handle the pressure of a gravitational drain system, so maybe 20 psi max. Since it doesn't have to be stronger than that, you are basically putting your nuts in the hand of the lowest bidder for the particular retailer you bought it at.

Threaded plugs - make sure they say NSF-pw on them.

Cleanout caps are not pressure rated.

Bell reducers are not pressure rated.

All fittings, bushings, couplers, reducers, etc should say NSF-pw on them.

Schrader fill valve should be threaded through 2 layers of pvc for safety, but if the plug is thick enough you will probably be fine.

williamfeldmann wrote:The reason that valves honk is the diaphram is bounding up and down on the seat inside the valve. Basically there is not enough air flowing to keep the diaphram open, (the spring is stronger than the flow of air). You mention that you are only running at low pressures currently and that is what is causing it.

What about the leak then? what would be causing the leak. We already cleaned it out and put white grease and we tested it out and the first shot was fine but then all the shots afterwards were leaking

I have an idea about the leak... It might simply be a leak around the threads. I had the same problem the other day, and it took me an hour to figure out, as I kept thinking it was the diaphragm. Also, try REALLY tightening down the screws and the solenoid. Also, I couldn't tell if you used hose clamps on the barb fittings. You might be getting a leak there, too. As to the honking, I have no clue. A blowgun should be more than adequate for piloting. I've personally tested my modded valve at only 10 psi, and it worked fine. I've never had a honk in my life. I would google the exact model number of the valve you are using, and see if you can find a picture of it taken apart. Then just compare your parts to the picture. Other than that, I'm out of ideas. Sorry!

Sorry, I missed the original leak reference. I assume the valve is still set up like in the pictures, with the solenoid still in place.

The leak is coming from, more than likely, one of two places. Either the diaphram is not seating fully, like there is some debris in the way, even the grease might be in the way; or the solenoid is allowing a little leak through the output port into the barrel.

The first thing I would do is take the solenoid out and plug that port. Using something like plumbers putty or epoxy, or any other such sealant, make sure that one or both of the little ports (one goes into the top chamber of that valve body, the other down into the outboard line of the valve) are fully plugged and sealed. This will make it so your valve can never be converted back to electric, not a huge deal.

If that did not fix the leak than my money is on the diaphram not sealing. This could be caused by a couple of things. Grime or obstruction in the way, spring not put back in right, etc. Start with taking the diaphram out and wipe up any gunk or excess grease that is inside the valve body, you can use water it won't hurt anything. When reassembling, put just film of plumbing grease or vaseline on the OUTER ring, where the screws are so that will seal, and on the inner ring of the valve body, not much, just enough so it will seal over any pits or scratches from the molding process. Replace the spring and make sure it seats properly inside the lid and on the diaphram.

The last reason, and often forgotten reason,that your valve may be leaking is that the equalization hole is not big enough to handle the speed at which you are filling the chamber. A sudden rush of air will pop open the valve. So with a small gun like yours, even a good bike pump could cause the gun to open prematurely. Try pumping it slow if using a bike pump or giving is slow steady pressure from a compressor. You can enlarge the equalization hole with a pin or needle. You do not need to take the whole white plastic piece out, just enlarge the hole a bit. It doesn't take much to make a big difference.

Try these things to see if you can get that valve sorted. And replace the DWV.

@pilgrimman

The threads leaking should be on the chamber side if the valve is working properly, add more teflon tape. That sort of thing is common, especially if you have to disassemble your cannon for transport. You shouldn't need to tape the threads on the barrel side. Hose claps should also seal quite well. They need to be tighter than you might have expected and should leave a permanent imprint in the hose.

Thanks for the help guys.:notworthy: First to go will be the DWV valve and the Epoxy, then we'll try the other stuff. Let you know how it turns out in a couple of days.

yeah thanks for the help.

I have had this same leak problem on occasion after modding a few Rainbird sprinkler valves...If you drill and tap your 1/4" blowgun fitting even slightly off center , sometimes this will interfere with the spring seat on the cover of the valve since you drill most of the spring seat away for your fitting...Even spring tension is no longer placed on the sealing face of the diaphram and you will have a slight leak on the outlet port ....The only way I was able to fix the problem on some valves was to replace the spring with a slightly heavier tension spring......I have since started using 1/8" fittings and have never had a problem again since it leaves more of the spring seat intact after modding. ...The problem was definitly caused during the modding of the valve since the valves sealed perfectly before modding for a blow gun.

EGOed wrote:I have had this same leak problem on occasion after modding a few Rainbird sprinkler valves...If you drill and tap your 1/4" blowgun fitting even slightly off center , sometimes this will interfere with the spring seat on the cover of the valve since you drill most of the spring seat away for your fitting...I have since started using 1/8" fittings and have never had a problem again since it leaves more of the spring seat intact after modding.

I wrote a mod program in the how to that would have saved you time on that. Also, when drilling the caps of the Rainbirds, drill from the inside of the cap. The small pinhole for the manual bleed provides a centering hold and then the drill follows the bleed port out. Perfectly centered holes every time.

Yeah william, unfortunately I saw your mod program after I started modding valves....Too bad cause it would have saved me some head scratching trying to figure out the problems I was having..It was strange because I didnt start having a problem until the 7th valve I modded so I assumed It was a defective valve diaphram...I replaced all the internals and it still leaked...I gave up on it until it happened again on another valve , so I decided to figure it out if it killed me.....after I saw your program I felt like slapping myself.....LOL....at least I got them all working finaly , 15 valves total....Have moved on to bigger and better things now ....Piston valves.