Valves holding a minimum upstream pressure so the far end of a system still gets water.
A pressure sustaining valve holds a minimum pressure on its upstream side. When a mainline cannot feed everything at once, it throttles the nearer laterals so the far end of the run, the elevated block or the filter backflush gets what it needs. This page covers in-line sustaining valves, normally open valves for filter stations, quick relief valves that protect the line from surges, and a hydrometer that meters and sustains in one body.
The lines here are from Bermad, Netafim and Rivulis, in glass-filled nylon and PVC for greenhouse and nursery duty and in iron for mainlines. ML Irrigation sells wholesale from Fountain Inn, South Carolina, and ships to growers in all 50 states.
Which type of pressure sustaining valve does my system need?
Start with the job, not the size. Four different jobs live in this category and the valves are not interchangeable.
In-line sustaining is the standard case. The valve sits on the mainline ahead of the zones you want to protect and holds a preset upstream pressure regardless of flow or downstream demand. Use it where a long run, an elevated block or a distant house starves while nearer laterals fill, and to control how the system fills at start-up. Bermad's IR-230, IR-130 hYflow and IR-430, Netafim's Series 75 and Series 80 and Rivulis's V3000 all do this.
Normally open sustaining is for filter stations. The Netafim PSNO Valve sits open and only throttles when upstream pressure drops, so a backflush keeps enough pressure to actually clean the screen. Bermad's IR-130 hYflow holds backwash pressure on in-field filter stations.
Quick relief is surge protection, not regulation. The Bermad 43Q Quick Relief opens fast on a spike from pump start-up or sudden valve closure, then closes slowly so it does not cause a second surge. Netafim's Quick Relief (QR) Valves sit fully closed while pressure is in range and open the instant it spikes, including on a power cut.
Combined bodies save a fitting: the Bermad IR-930 Hydrometer meters and sustains in one valve, and the Rivulis V3000 comes as a combined reducing and sustaining valve. If the problem is too much pressure downstream rather than too little upstream, you want a pressure reducing valve instead.
What do the water, pressure and wiring need to be?
Check three numbers before you order. First is the pressure you need to hold, which must fall inside the pilot spring range. Bermad's IR-230-55 offers four springs from 3 to 150 psi, Netafim's Series 80 runs three color-coded ranges from 7 to 90 psi, and a valve with the wrong spring either never throttles or never opens. Second is inlet pressure: the plastic Bermad bodies are rated to 150 psi, Netafim's Series 80 runs to 150 psi and the Series 75 to 145 psi, and the Rivulis V3000 is rated to 145 psi, or 232 psi in sizes over 6 inches. Third is flow, which sets the size. Size a control valve on flow, not pipe diameter; an oversized valve regulates poorly at low flow.
Water matters too. The pilot works through small passages and needs clean water, so on a pond or well feed put a screen ahead of it. Netafim's Series 75 and Series 80 nylon valves are rated for water to 140°F.
Wiring only applies if the valve must also open and close on a signal. The Bermad IR-230-55 takes an AC solenoid or a DC latching solenoid for battery controllers, and Netafim's Series 80 is ordered as PSELTH for the electric version. The IR-130 hYflow is available with solenoid control and the Rivulis V3500 in an electric version; the rest are hydraulic and need no power. Send us the elevation change, run length and flow with your quote request and ask us which valve fits.
What goes wrong, and how do the Bermad, Netafim and Rivulis lines differ?
The mistake we see most is confusing sustaining with reducing. A reducing valve protects what is downstream from too much pressure; a sustaining valve protects what is upstream from too little. Put a reducing valve where you needed a sustaining valve and the far block still starves. Next is the spring: the setpoint lands outside the pilot range and the valve never regulates. Then there is skipping relief on a system with a large pump, and splitting a mainline on the first power cut. Last is setting relief too tight so it weeps all day; the Netafim QR is typically set to open about 10 psi above working pressure.
The three lines take different routes to the same job. Bermad is the control-valve specialist: glass-filled nylon 200 Series and hYflow bodies for greenhouse and nursery work, the cast iron 400 Series IR-430 for mainlines, and the widest pilot spring choice on this page. Netafim builds the Series 75 as a one-moving-part nylon valve and, on the Series 80, mounts every pilot and solenoid on the bonnet so no control tubing runs to the body. Its PSNO Valve is the filter-station valve, in PVC from 3 inches and iron up to 12. Rivulis goes metal from the start: the V3000 uses a springless diaphragm and runs from 1 to 16 inches, and the V3500 piston valve is the pick where you want maximum control on 2 to 10 inch lines.
Frequently asked
What is the difference between a pressure sustaining valve and a pressure reducing valve?
A reducing valve limits pressure downstream of itself, protecting drip tape or emitters from a supply that runs too high. A sustaining valve holds pressure upstream of itself, throttling flow so the zones or filter behind it keep their minimum. Many systems need both, and Rivulis offers the V3000 as a combined reducing and sustaining valve so the two jobs share one body.
Can a pressure sustaining valve also open and close from my controller?
Yes, on the electric versions. The Bermad IR-230-55 adds a solenoid to the sustaining pilot, in an AC version or a DC latching version for battery controllers, so one valve both prioritizes a zone and switches it. Netafim's Series 80 is ordered as PSELTH for the same function. The hydraulic versions need no wiring at all.
Which valve holds pressure during a filter backflush?
A normally open sustaining valve. Netafim's PSNO Valve sits fully open in normal running and only throttles when upstream pressure drops, so the flush keeps enough pressure to clean the screen and the filter comes back online faster. It comes in PVC from 3 inches and in iron up to 12 inches. Bermad's IR-130 hYflow holds backwash pressure on in-field filter stations.
How do I pick the pilot spring range?
Choose the spring whose range contains the pressure you want to hold, ideally toward the middle rather than at either end. Bermad's IR-230-55 offers four springs from 3 to 150 psi, and Netafim's Series 80 runs yellow 7 to 30 psi, green 14 to 65 psi and red 30 to 90 psi. A spring that tops out below your setpoint will never hold it.
Who does ML Irrigation sell to, and does it ship outside South Carolina?
ML Irrigation sells wholesale to production nurseries, greenhouse operations and horticulture education programs, and ships to growers in all 50 states from Fountain Inn, South Carolina. Send us the run length, elevation change, flow and the pressure you need to hold with your quote request, and ask us which valve fits the job.
