why is my pressure washer leaking water from the bottom of the pump when it’s running

Diagnosis

Water leaking from the bottom of the pump housing on a Briggs & Stratton S2200 typically indicates a failure of the internal high-pressure seals or a breach in the pump manifold. Because this unit utilizes an axial cam pump, the seals are subject to significant friction and heat. When the seals wear down or harden due to age or lack of lubrication, water bypasses the seal and drips from the lowest point of the pump casing, often appearing as a steady drip or a spray during operation. This specific leak is often exacerbated by "dry running," where the pump is engaged without a steady water supply, causing the seals to overheat and crack. To confirm the leak is internal, wipe the entire pump housing dry with a microfiber cloth and run the machine for 60 seconds. If water emerges from the seam where the pump head meets the crankcase or from the area surrounding the plungers, the internal seals have failed. If the water is coming from a specific threaded plug at the bottom, it is likely a loose drain plug or a failed O-ring.

How to Fix It

To resolve a leak coming from the internal seals of the S2200 pump, you must replace the seal kit. This requires a set of metric sockets, a snap-ring plier, and a replacement seal kit compatible with the S2200 axial pump assembly.

1. Shut down the engine and disconnect the spark plug wire to prevent accidental starting. Disconnect the high-pressure hose and the water inlet hose.
2. Remove the four mounting bolts securing the pump housing to the engine crankshaft. Carefully pull the pump assembly away from the engine.
3. Using a snap-ring plier, remove the retaining clips from the end of the pump manifold.
4. Slide the pump head off the manifold to expose the plungers and the seal cups.
5. Remove the old, worn seals using a small pick. Be careful not to scratch the inner bore of the pump housing, as any scoring will cause the new seals to leak immediately.
6. Clean the seal seats with a lint-free cloth and a small amount of silicone lubricant.
7. Insert the new seals from the kit, ensuring they are seated flush against the housing. Press them firmly into place using a rubber mallet or a seal driver tool.
8. Reassemble the pump head, reinstall the snap-rings, and bolt the pump back to the engine, ensuring the mounting bolts are torqued evenly to prevent housing warp.
9. Reconnect the water source and run the pump for 2 minutes without the nozzle attached to bleed air and lubricate the new seals before applying full pressure.

If That Didn't Work

• Check the Drain Plug O-Ring: If the leak is localized specifically at the bottom drain plug, remove the plug and inspect the rubber O-ring. If it is pinched or cracked, replace it with a Viton O-ring of the same diameter. Apply a small amount of waterproof plumber's grease to the threads before tightening.
• Inspect the Manifold for Hairline Cracks: If new seals don't stop the leak, the aluminum pump housing may have a stress crack, often caused by freezing water left in the pump during winter. Use a flashlight to inspect the casting for vertical cracks. If a crack is found, the entire pump assembly must be replaced as these cannot be reliably welded.
• Verify Inlet Fitting Seals: Sometimes water leaks from the inlet connection and runs down the side of the pump, making it look like a bottom leak. Replace the inlet garden hose O-ring and ensure the fitting is tightened with a wrench, not just hand-tight.
• Replace the Unloader Valve: If water is leaking from the area near the trigger valve (unloader), the internal valve seat may be worn. Replace the unloader valve assembly to prevent water from bypassing the pressure chamber and leaking through the housing seams.

Heads Up

• Never Run Dry: Always ensure water is flowing through the pump before starting the engine. Running the pump dry for even 30 seconds can melt the seals and ruin the pump.
• Winterization: Always drain the pump completely before storing it for winter. Use a pump saver or antifreeze solution to prevent water from freezing inside the manifold, which is the leading cause of housing cracks.
• Water Quality: If you are using well water with high sediment, install an inline sediment filter. Sand and grit will act like sandpaper on the internal seals, shortening their lifespan significantly.
• Avoid Over-Tightening: When reinstalling the pump housing, do not over-torque the bolts. Over-tightening can warp the aluminum casting, creating new leak paths.