PGV-100 vs PGV-101: which Hunter anti-siphon valve to use

An anti-siphon valve is an irrigation control valve with an atmospheric vacuum breaker built into the body. The vacuum breaker sits above grade between the supply line and the downstream zone outlet, and it physically prevents the zone pipe from siphoning irrigation water (and whatever's dissolved in it) back into the potable supply when supply pressure drops. For residential systems on a code path that accepts atmospheric vacuum breakers, the anti-siphon valve replaces a separate backflow device: one fitting on the wall does both jobs.

Hunter's PGV anti-siphon line comes in two variants. The mechanical difference between them is a single component: flow control.

The only material difference: flow control

Both the PGV-100 and the PGV-101 anti-siphon valves use the same valve body, the same diaphragm, the same 24V solenoid, and the same atmospheric vacuum breaker assembly. The single mechanical difference is a flow-control stem on top of the PGV-101.

Flow control is a stainless steel screw that rides on the valve seat. Turn it down and it throttles how far the diaphragm can lift off the seat when the solenoid energizes, reducing downstream pressure and flow at the valve outlet. Turn it back out and the valve runs wide open. The PGV-100 omits the stem; the diaphragm lifts to its full travel every cycle, and downstream pressure equals supply pressure minus the valve's small fixed pressure loss.

When the PGV-101 (flow control) earns its place

Flow control is a pressure-tuning lever at the head of the zone. Three install profiles want it:

• Long lateral runs where head-of-zone pressure runs well above nozzle spec. Static supply pressure of 70+ PSI is common on municipal lines in the Southeast and Southwest. Spray nozzles specified at 30 PSI mist visibly at that supply pressure; throttling the valve down to 35–40 PSI at the outlet ends the misting at the source, before any per-head regulation is in play.
• Mixed-head zones where the closest sprinkler over-pressurizes. A single zone with three heads near the valve and three at the far end will run the near heads at near-supply pressure and the far heads close to spec. Flow control trims the whole zone toward the spec range so the near heads stop misting without starving the far heads.
• Multi-valve manifolds where you want per-zone pressure tuning at the valves. Cheaper than installing a downstream pressure regulator at each zone; faster to adjust seasonally as supply pressure shifts.

Per Hunter, the PGV body is rated for 20–150 PSI inlet pressure, so the flow-control stem can absorb a wide supply swing without stressing the diaphragm.

When the PGV-100 (no flow control) is enough

Short residential runs on a single-head-type zone don't need pressure tuning at the valve. If supply pressure sits in the 30–60 PSI band and every sprinkler in the zone is the same family, the nozzles handle the pressure themselves. Pressure-regulated spray bodies (Hunter's PRS30 and PRS40 Pro-Spray lines) make a flow-control valve redundant for that install: each head regulates its own outlet pressure, so trimming at the valve buys nothing.

Code path and what an anti-siphon valve actually covers

The PGV anti-siphon body carries an integral atmospheric vacuum breaker (AVB). Where local code accepts an AVB as the backflow assembly for residential irrigation, the anti-siphon valve is the whole device. Installs that require a pressure vacuum breaker (PVB) or reduced pressure zone (RPZ) assembly need a dedicated backflow preventer upstream of the zone manifold; the PGV-100 or PGV-101 by itself won't satisfy that code path. Check the local jurisdiction before you spec, especially on commercial installs and cross-connection-controlled water districts.

Featured Hunter PGV anti-siphon valves in stock

The PGV-101-ASV (anti-siphon, with flow control) is stocked across the common pipe-thread combinations below. The without-flow-control PGV-100-ASV is available by special order; for that path or for the rest of Hunter's valve catalog, see the Valves category page.

• HUN-58-1107 / PGV-101-ASV, 1" FIPT. The 1" anti-siphon valve with flow control. FIPT inlet and outlet; pairs with standard 1" PVC manifolds and the most common residential lateral size.
• HUN-58-1162 / PGV-101-ASV, 3/4" Slip. Three-quarter-inch body with slip (PVC solvent-weld) connections, for laterals on 3/4" PVC where a glued joint is preferred over threaded.
• HUN-58-1106 / PGV-101-ASV, 3/4" FIPT. Three-quarter-inch body with female pipe thread. Stock is intermittent; the 1" FIPT above is the higher-volume SKU and ships from inventory most of the year.

Keep going

For the full Hunter anti-siphon and inline valve catalog, see the Valves category. If the install needs a dedicated upstream backflow device (PVB or RPZ assembly), see Backflow Preventers. For the broader product line, browse the Hunter brand catalog.