Drip Irrigation: Old Diaphragm Restricts Flow, Emitter Pressure, Backflow Preventer Maintenance

Three questions: (1) Does old diaphragm restrict flow? (2) What pressure for 1‑2 GPH emitters? (3) 30‑yr‑old Febco 765 PVB no longer drips on startup – is it causing water hammer?

Answers

1. Yes, worn diaphragms restrict flow and eventually fail.
2. Emitters need 20‑30 PSI; exact GPH varies.
3. PVB poppet/seat can be replaced. No drip on startup is normal if not leaking constantly. PVB does not relieve pressure; water hammer is from valve closing too fast. Reduce flow control on the banging valve.