c-ed wrote:....The drain valves are not repairable and with time will stop working altogether....
I don't know what drain valves the 180 uses but the ones used on the metal-tanked Cessna's (SafAir 110,170, etc) are repairable, at least to the extent of replacing the o-rings. O-ring damage is quite often the problem when they quick-drain won't quit dribbling. Sometimes the little holes in the quick-drain stem plug up with debris, sometimes the top of the stem itself rots out from continual immersion in water-- usually on a ramp or hangar queen which seldom gets the water drained out.
My tip for replacing these without draining the fuel tank first is to have a spare ready to go or use a temp plug while you replace the O-ring on the old quick-drain, and to tie an old sock or something around each wrist while doing the change-out to avoid getting an armpit full of gas.