I changed out the larger original gate valves on our 28.5 years ago to ball valves from WM. The ball itself is polished stainless, the body is bronze and the ball appears to have a teflon or nylon seat separating stainless from bronze. I initially used a couple Forespar Marelon ball valves but one became bound up and the handle broke off. Since they cost about the same and there was no replacement policy at the time from Forespar, it too was replaced with the bronze / stainless ball valves. One 3/4 Marlon remains on the head intake. Check the thread size and type in the store by screwing a bronze thru hull into the ball valve and the appropriate straight or elbow fitting into the top end.