Why a Drip Conversion Causes a Valve to Not Close Fully

After replacing bubbler heads with 8-way drip emitters on 1/4" tubing, a Rain Bird APAS 3/4" anti-siphon valve won’t shut off completely. Water seeps from the anti-siphon vent and the drip heads when the zone is off. Cleaning the valve didn’t help.

The Problem: Flow Too Low for the Valve

The valve requires a minimum flow differential between open and closed states to seal properly. Converting to drip drastically reduced the flow, so the valve can’t distinguish “on” from “off” and stays partially open.

Solution: Install a Low-Flow Valve

Replace the existing valve with one designed for low-flow drip systems (often called a “low-flow valve” or “drip valve”). These valves operate reliably at flows as low as 0.5–2 GPM. Consult an irrigation supplier with your exact flow rate to select the correct model. If your contractor can’t resolve it, provide them with the flow details and ask for a low-flow valve replacement.