So, I'm finishing up the return section on my 55, and instead of putting a check valve in it, started to think about anti-siphon holes in the u-tubes. The tank has a 700 gph return pump that t's off into two half inch u-tubes. If I were to drill anti-siphon holes, where should they be on the u-tubes? I read something about putting them 1/4 in below the waterline, but I need to confirm this. Thanks.
