Batboard

I am going to mount a DB224 on a hand rail on the side of an elevated water tank. The antenna will be totally shielded in one direction. Will it be better to adjust the diopoles on the antenna in the omni pattern or all on the same side of the mast? I want the best coverage in 3 directions away from the tank.

Leave it omni if you are trying for 270 deg coverage from that mount. You will be getting 180 deg coverage plus a little. It will effectively be a cardioid pattern with a 20db null towards the tank.