Resetting your pressure relief valve

The pressure relief valve (PRV) is a safety device that protects your watermaker from over-pressurisation. The system's nominal operating pressure is 800 psi, but the high-pressure pump can build more than twice that.

To protect your components, the PRV is factory-set to open and dump pressure if it ever climbs above 1050 psi.

How to tell it needs resetting

The system suddenly drops to around 200 psi, usually while you're dialling the pressure up towards 800 psi.

Why it happens

The PRV is regulated by a stainless steel spring. Stainless springs don't have the same "memory" as high-carbon steel springs, so the valve may need resetting once or twice over the life of your watermaker.

Steps

1. Plug the discharge line. Remove the hose from the PRV, which is on the high-pressure pump, and plug the end. The hose is teed into the discharge circuit, so plugging it stops water spilling out.
2. Set up a temporary line. Run a temporary 1/2" hose from the hose tail on the PRV into a bucket. Don't fit a hose clamp.
3. Bottom out the valve. Loosen the lock nut on the PRV, then wind the cap nut, with the hose tail attached, all the way in until it bottoms out.
4. Bring the system to 1050 psi. Run the watermaker following your quick start guide, and slowly bring the pressure up to 1050 psi. Take care not to let it go any higher.
5. Set the relief point. Slowly unwind the cap nut on the PRV until the valve opens. This usually happens suddenly. As soon as it does, quickly wind down the pressure on your main control valve. When the pressure drops to around 200 psi the PRV's internal poppet will re-seat. Keep unwinding the control valve to zero pressure, then shut off the high-pressure pump.
6. Lock it down. Tighten the lock nut to hold the new setting, then reconnect your original discharge hose.
7. Test run. Start the watermaker as normal and confirm it holds pressure at 800 psi.