Pressure Washer Pump Will Not Prime After Storage: Water Supply and Airlock Checks
If a pressure washer pump will not prime after storage, begin with the incoming water and trapped air—not with pump disassembly. A pressure washer that ran normally before being parked can seem like it has a failed pump when the garden hose is restricted, the inlet screen is plugged, a connection is pulling air, or an air pocket remains in the pump and hose.
Safety first: Keep the engine or electric motor off while connecting hoses, inspecting the inlet, and bleeding air. For electric models, keep plugs and cord connections dry and use the equipment only as directed in its exact owner’s manual. Never run the pump without a confirmed water supply.
This guide covers the sensible first checks when a pressure washer pump will not prime after storage. It applies to many homeowner pressure washers connected to a pressurized garden hose. It does not apply to setups intended to draw from a tank, pond, or other standing-water source unless that specific machine is designed and equipped for that use.
What “will not prime” usually looks like
After storage, the phrase can describe a few different symptoms:
- The engine starts or electric motor runs, but little or no water comes from the spray gun.
- The unit produces a weak, sputtering stream rather than steady flow.
- The hose and gun feel normal at first, but pressure never builds.
- The pump sounds loaded or the water flow pulses after winter storage.
A true internal pump problem is possible, especially if the unit froze while stored. But first rule out water starvation and air in the system. Those checks are quicker, lower-risk, and often solve a pressure washer will not draw water complaint without replacing parts.
Pressure washer pump will not prime after storage: diagnostic order
Work through these checks in sequence. Do not skip directly to the pump, because a restriction upstream of it can create the same no-prime symptom.
- Confirm the water source is fully on and adequate.
- Flush the garden hose before connecting it to the pump.
- Inspect and clean the pump inlet screen.
- Check hose ends, washers, and couplers for an air leak or blockage.
- Purge air through the gun with the machine off.
- Check the spray tip and downstream attachments if flow reaches the gun but pressure is poor.
- Look for freeze damage, leaks, or other signs that point to an internal pump fault.
1. Start with the garden-hose water supply
A pressure washer pump cannot make up for a weak or restricted supply. Before attaching the hose, open the outdoor spigot and let water run through the hose for a short time. This clears stale water, loose debris, and air from a hose that has been sitting through a season.
Watch the stream from the free end of the hose. It should be steady, not interrupted by spurts of air. If the flow is weak, inspect the hose for sharp kinks, crushed areas, a partially closed shutoff, or a clogged hose-end washer. A long, undersized, damaged, or heavily coiled hose can also limit supply.
Do not assume a spigot that works for hand watering provides enough flow for every pressure washer. Supply requirements vary by model. For example, Simpson advises checking that the water source can provide at least 5 GPM at 20 PSI for the models addressed in its guidance, while Briggs & Stratton notes model-specific minimum supply requirements. Use the requirement in your own manual instead of treating one published number as universal.
2. Clean the inlet screen before trying to start it
The small screen at the pump’s garden-hose inlet is one of the most important checks when a pressure washer pump will not prime after storage. It protects the pump from debris, but sediment, mineral scale, bits of deteriorated hose washer, or storage debris can restrict flow enough to prevent normal priming.
With the water turned off and the garden hose disconnected, locate the inlet screen just inside the pump connection. Remove it only as your manual directs. Rinse a dirty screen with clean water and inspect it closely. Replace it if it is torn, distorted, or damaged. Do not operate the pressure washer with the screen missing; it is there to protect the pump.
Also examine the hose washer at the pump inlet. A washer that is split, flattened, missing, or folded out of place can both leak and interfere with the connection. Tighten the garden hose by hand. Avoid forcing fittings or overtightening plastic inlet connections.
3. Eliminate a pressure washer airlock after winter storage
A pressure washer airlock after winter storage is a common reason for sputtering water or a pump that seems unable to pick up water. The goal is to send water through the inlet, pump, high-pressure hose, gun, and wand before the engine or motor is asked to run.
Basic air-purge method
- Leave the engine off or the electric unit switched off and unplugged as appropriate.
- Connect the garden hose to the pump inlet and the high-pressure hose to both the pump and trigger gun.
- Confirm the spray tip and wand are correctly attached. If your manual permits it, removing a blocked tip can help isolate a downstream restriction, but do not point the gun at people, animals, or property that could be damaged.
- Turn the water supply fully on.
- Hold the spray gun securely, point it in a safe direction, and squeeze and hold the trigger.
- Wait for water to flow in a steady stream with minimal sputtering. This may take longer after a long storage period.
- Release the trigger only after steady flow is established, then start the unit according to the exact owner’s manual.
Generac’s owner guidance similarly calls for turning on the water and squeezing the trigger to purge air from the pump system before operation. Simpson’s troubleshooting guidance recommends flushing air from the disconnected supply hose first, reconnecting it, and then squeezing the trigger to remove remaining air.
If you still have intermittent pressure after air is purged, see our related guide on pressure washer pulsation, water supply, and air checks. Pulsing can indicate lingering air, but it can also point to another restriction or a pump/unloader issue.
4. Check for suction-side air leaks and connection problems
Most homeowner units are fed by normal household water pressure, so they do not “suck” water in the same way as a dedicated transfer pump. Still, a poor inlet connection can admit air or limit incoming water. That can make it appear that the pressure washer pump is not pulling water.
Inspect these areas with the machine off:
- The garden hose washer at the pump inlet.
- The inlet screen and its seating position.
- The garden hose fitting for cross-threading or cracks.
- A quick-connect adapter, if your unit uses one.
- The hose itself, especially sections that may have frozen, been pinched, or been run over during storage.
- Any inline filter, shutoff valve, backflow device, or accessory between the spigot and pump.
Use only the plumbing arrangement allowed by your pressure washer manual. Some manuals specifically warn against putting one-way valves, vacuum breakers, or check valves in the water-supply line because they can interfere with proper supply to the machine.
5. Separate a no-prime problem from a clogged nozzle
If water flows freely from the trigger gun with the tip removed but pressure is weak or absent with the tip installed, the pump may be receiving water normally. The likely issue is farther downstream, such as an obstructed spray tip or wand screen.
Shut the machine down, relieve pressure through the trigger, and follow the manual’s nozzle-cleaning procedure. Do not enlarge the nozzle opening or use a drill bit, nail, or other improvised tool. A damaged orifice changes the spray pattern and can affect pressure and pump loading.
For a step-by-step approach focused on that component, read how to clear a clogged pressure washer nozzle without damaging the orifice.
6. When storage damage becomes more likely
If the water source is strong, the inlet is clear, air has been purged, and water still will not move normally through the pump, inspect for visible evidence of freeze or storage damage. Look for cracks in the pump housing, water leaking from the pump body, damaged fittings, or milky pump oil on models with a serviceable oil-filled pump.
A frozen pump can have internal damage even when an external crack is not obvious. Do not keep running a unit that has no water flow, abnormal leaking, or signs of pump damage in hopes that it will clear itself. Continued operation can make the repair decision less favorable.
For help deciding what visible freeze symptoms mean, see pressure washer pump freeze damage: cracks, leaks, and replacement decisions.
When to stop troubleshooting and get help
Consult the exact owner’s manual or an authorized service professional if any of these apply:
- The pump housing, manifold, fitting, or hose connection is cracked or actively leaking.
- The unit was stored where freezing was possible and now has no flow after the supply and airlock checks.
- Water reaches the pump but will not exit the pump outlet when tested only in the manner authorized by the manufacturer.
- An electric model trips protection, has a damaged cord, or shows any sign of electrical trouble.
- The engine starts but stalls hard when the trigger is used, which can involve pump load or the unloader system rather than priming alone.
The practical takeaway is simple: when a pressure washer pump will not prime after storage, give it a clean, unrestricted water supply and deliberately purge air before concluding the pump has failed. A flushed hose, intact inlet screen, sound hose washer, and steady trigger-gun flow are the basic conditions the pump needs before you move on to more involved diagnosis.
