SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

As I understand it, flow control is when a valve has a knob that you use to restrict the flow of water through the valve. It essentially works like turning your hose bibb way down. Same thing with your sinks. You turn the knob on just a little to get a little water, or on full to get as much water as possible. When a valve doesn't have flow control, it basically means it acts like a sink knob with two positions, off and on.

Why don't you use 8' nozzles instead of the 12'?

Or use a double row of strip nozzles.

Flow controls work to restrict water flow as mentioned before. I find them very useful for two puposes: reglate pressure at the heads so they don't fog, and to restrict the flow thru valves giving backpressure so the cavity area above the diaphragm can build pressure and the valve can close properly. Drip valves, in particular, have a real problem getting enough back pressure to close, especially if there's a very small volume flowing through the zone to start with. There HAS TO BE a differential of pressure between upstream and downstream sides of the valve or it won't close.... period. By restricting the flow through the bibb/valve seat, that differential is acheived. (I'm generally talking PIN type valves here, of course.)
Bill