In addition to check valves (which i dont trust)make sure you have a siphon break in your return if you'er running a sump _________ 135g 3" SB 3- 400w MH, 2 65w PC actinic, 2 10K PC, 40g refugium, EV-180 PS ,Mag 18 ret,1700 PH,2 maxi 1200's air water and ice 5 stage RO/DI  |