Roto-Flow enables equal distribution to your leaching fields. Available in 3" and 4" sizes. The Roto-Flow gives you the low cost solution to your D-Box flow regulating problems. The simple Roto-Flow for D-Box outlet pipes gives you the easiest "set & forget" flow regulator available. The Roto-Flow fits both Schedule 40, SDR 35 and thin wall pipe sizes. Simply place the Roto-Flow into the D-Box outlet pipe, and adjust to equalize flow.