Check Valves

Water in a pressure washing system needs to move one direction, and a check valve is the part that enforces the rule. Sun Brite Supply carries brass and stainless steel check valves from 1,200 to 6,500 PSI for chemical lines, float tanks, and pump circuits. Not sure which size or rating your rig needs? Call 301-519-9274 and describe your setup, we spec these all day.

How to Pick the Right Check Valve

Three decisions cover almost every check valve purchase: pressure rating, material, and port size. Get all three right and the valve disappears into the system and just works. Get one wrong and you either blow the valve apart or corrode it shut inside a season.

Pressure rating. A 1,200 PSI brass check valve belongs on the low-pressure side: float tank feeds, detergent lines, buffer tank plumbing, supply circuits. Put that same valve downstream of the pump on a 4,000 PSI machine and you are gambling with a part that was never rated for the job. High-pressure circuits need a valve built for them, like a 6,500 PSI stainless unit rated for the flow your pump actually produces.

Material. Brass handles plain water and mild detergents fine and costs less. Stainless steel is the right call anywhere sodium hypochlorite, acids, or aggressive degreasers pass through, because those chemicals eat brass internals and the first thing to fail is the sealing surface. If you soft wash, the extra ten to twenty dollars for stainless buys you a valve that still seals next year.

Port size. Match the valve to your line size and flow. An undersized check valve is a flow restriction with threads. The valve should pass your full GPM without becoming the bottleneck, which is why the high-flow stainless units carry both a PSI and a GPM rating.

How a Spring Check Valve Works

The spring holds a ball or poppet against a machined seat. Forward pressure lifts it and water flows. The moment flow reverses, the spring and the back pressure slam it shut. Simple, which is exactly why the usual failure is not the mechanism breaking but debris or dried chemical holding the ball off its seat.

Where Check Valves Go on a Washing Rig

Downstream injectors have a check valve built in so high-pressure water cannot shove back up the soap line and burst your chemical jug. Float tank and buffer tank feeds get one so tank water cannot drain backward when supply pressure drops. Rigs that draw from two sources use them to keep one supply from pushing into the other. And inside the pump head itself, inlet and discharge valve assemblies are check valves too, which is why a pump that loses pressure often just needs a valve kit rather than a new pump.

Check Valve Comparison

Confirm current pricing on the product page or give us a call before ordering.

From the Field

The check valve complaint we hear most has nothing to do with the valve wearing out. It is soap residue. Crews run bleach mix or thick detergent through an injector, park the rig for the weekend, and the chemical dries into crystals that glue the check ball to its seat. Monday morning the injector pulls nothing. The fix costs nothing: draw a gallon of clean water through the chemical line at the end of every shift. The second lesson comes from the pump side. We sell steady numbers of pump check valve assemblies because those internal valves take a beating from cavitation and hot bypass water. If your pressure is falling off and the unloader checks out, pull the valve caps before you blame the pump.

Related Collections

• Chemical injectors, the most common home for a check valve
• Thermal relief valves and pressure relief valves
• Safety relief valves and easy start valves
• Float valves for buffer tank fills
• Ball valves for manual shutoffs
• Brass pipe fittings and stainless steel pipe fittings
• Unloader valves if pressure problems persist
• Pick up locally at our Gaithersburg store

Frequently Asked Questions

What does a check valve do on a pressure washer?

It lets water flow one direction and blocks it from flowing back. On a washing rig that protects chemical jugs from high-pressure blowback, keeps tanks from draining in reverse, and keeps one water source from pushing into another.

Why did my downstream injector stop pulling soap?

The most common cause is a stuck check ball. Dried chemical glues the ball to its seat so the injector cannot draw. Flush the injector with clean water, and if it is still dead, free the ball gently and rinse the debris out. Flushing after every job prevents it.

Should I buy a brass or stainless steel check valve?

Brass for plain water and mild soaps on a budget. Stainless anywhere bleach, acids, or strong degreasers flow through, because those chemicals corrode brass seats and the valve stops sealing.

What pressure rating does my check valve need?

Rate the valve for the highest pressure it will ever see, not the average. Supply and chemical lines are fine at 1,200 PSI. Anything plumbed after the pump needs a high-pressure valve, like a 6,500 PSI stainless unit.

Which direction does a check valve install?

Follow the flow arrow stamped on the body, pointing the same direction the water travels. Install it backward and the system dead-heads instantly, which feels like a total blockage because it is one.

Are the check valves inside my pump the same as inline check valves?

Same principle, different part. Pump head inlet and discharge valves are spring check valves sold as OEM assemblies matched to your pump model. When a pump loses pressure with a good unloader, worn internal check valves are the usual suspect.