I built a similar system using 3 corny kegs about a year ago and keep about 150 balls pressurized in them for use in my ball machine (a Silent Partner Star). I already had the kegs and tubing from my old homebrewing days as well as a nice car tire pressurizer so I think I spent less than $10 in additional parts to complete the system. The only downside I've found is that it takes a bit of time getting the balls into and out of the kegs between uses.
What I do is try is use the balls during a three day period, for example I unload them on a Friday and then leave them unpressurized until after using them the next Sunday when I put them back under pressure. This cuts down on the time spent just moving balls into and out of kegs. I timed it once and it takes about 1.5 seconds per ball grabbing them three at a time, and since a keg typically holds about 65 balls it takes a little under two minutes per keg to load or unload or about 5 minutes total for all the balls I want to use, which is really not that big of a deal.
To jrxl, I'm not leroy obviously but I don't see much pressure loss even over an extended period of time in the keg. I don't use as much pressure as leroy does (mine was determined through trial and error) so his results may be different. I did spend a good bit of time getting the kegs to seal properly by replacing old gaskets and using a keg lube/sealer product on them.
When should you serve and volley in doubles? Only when you want to win.
Last edited by beernutz; 11-05-2012 at 01:19 PM.