Ok, we need a picture. This isnt a corny keg. I dont have a bottom valve on my corny keg, and I dont have a lid that unscrews. We can help get you going, but we need to know what kind of keg is it. Is it plastic, stainless? Corny kegs hold like 120psi (or so). You said 40 pints, so I guess we're not talking about 5L kegs. Sorry but I am confused, and interested in what type of keg this is. We'd like to figure this out, to help you and others who find themselves in the same situation.
Primaries: Mojave Red (AG)
Kegs: Hibiscus Saison (AG), Orange Kolsch (AG) , Cocunut Porter
Future Brew: Wee Heavy