Our 1991 # 277 coach has three Thetford part # 08671 drain valves installed. The curb side bus dump is leaking. Are the valves (two are on the driver's side) glued in place, or just siliconed in? I'm trying to determine how to remove and rebuild while causing the least damage to the piping. Removing the valves appears to be the most difficult part of the repair. Thanks!
Danny