Directional Eyeball Fittings
Pool directional fittings, aka pool eyeball fittings, are used to direct the flow of water entering the pool through the pool return. In general, a circular flow pattern is best, with deep end returns sweeping filtered water through the deep end. Other returns can be set to create a slight surface ripple, to encourage leaves to move closer to the skimmers. Pool eyeball fittings are sized to create more or less pressure at different pool returns.
Returns closer to the pump may utilize a smaller orifice, while those located further away have a larger opening, to balance the flow between the two. Eyeball fittings for pools are also connected to the return pipe in two ways, slip or threaded, both 1.5 inch.
For threaded wall fittings, use the threaded MIP (male internal pipe threads) eyeball fittings. For smooth 1.5 inch returns, use the Slip (smooth) eyeball fittings, without threads, which push in place, inside the pipe (also known as insiders).