I have two skimmers, a pair of main drains in the deep end, and another pair of main drains on the wall in the shallow end. The pair of main drains in the shallow end were evidently a mistake because no matter what I do they never suck water in. I have two valves for water coming in. One valve controls BOTH skimmers. The other valve controls the main drains in the deep end. Does this sound right? I showed this to my builder and he didn't have an answer about the main drains in the shallow end, but said both skimmers should be on one valve, just like it is. Looking for some advice from those who know better.