1.5" would be good but I'd use either rigid pvc or spa flex as vinyl tubing kinks. I'd run a single line all the way to the skimmer and tee it off into two 1" lines as close to the inputs as possible.

In regards to the air flow it seems to me the air pump is doing all the work. IMO it sort of defeats the purpose of the Beckett which requires such a large pump. The Beckett is just a venturi which a designed to reduce static pressure enough to suck in air but you only need reduce the static pressure in the line to atmospheric in order to maintain the same flow from the air pump. Hence the venturi is much more restrictive that it actually needs to be if used with an air pump. What this means if you increase the cross sectional area in the venturi you could use a much smaller pump yet still obtain identical results. Not sure if that's much concern to you but these types of things drive me nuts.

For now I'd consider increasing your pipe size, measure results before and after (without air pump). I won't hurt, how much it helps depends on how restrictive the Beckett is and what the resulting velocity is. Also what about the impeller upgrade, did you look into that? These are things I would consider prior to buying new pumps if the goal is to remove the air pump.

thanks for the advice.

skimmerking: there is no ball valve. the one in the photo is for the return pump to the tank.


sphelps: i've always been told that pvc pipe was far more restrictive than vinyl tubing because of the rigid 90s that would be involved.. From the pump to the splitter im running the braided kind to avoid kinking. from the splitter i used non braided because i needed the flexibility, but still made sure not to kink it.

I will try it with 1.5" piping and see what happens.