Fix your water problem and you won't need to keep draining it.

Two areas to check....the obvious is the vent line near the right spring.

A commonly ignored spot is where your brake line Tee attaches to the axle tube. If this bolt gets loose, you will get water in the housing. Make sure it is tight...better yet, pull it off and put some RTV under it before you put it back on.

Also make sure your not getting water in through the axle tube to pumpkin area. It won't hurt anything to run a bead of RTV around the seam...they only weld it in 3 or 4 places. (ok, that's 3 areas)