How to Winterize a Pressure Washer: Complete Guide

A pressure washer that sits all winter with water in the pump is a pressure washer that won't work next spring. The water freezes, expands, and cracks the pump housing or the valves. Winterizing takes 15 minutes and prevents a $100+ pump replacement. Here's how.

Why Winterizing Is Critical

Pressure washer pumps are precision devices with close-fitting ceramic plungers, brass valves, and rubber seals. When water freezes inside the pump:

• The ice expands and cracks the pump body
• The valves distort and leak
• The seals dry out and crack

Even if the pump doesn't freeze, water left inside corrodes the internal components over months of storage. And the fuel in the engine goes stale, clogging the carburetor.

Winterizing addresses all three: water, fuel, and pump protection.

Step 1: Flush the System

Before winterizing, flush out any chemicals or detergent:

1. Connect a garden hose to the inlet
2. Turn on the water and let it run for 1–2 minutes
3. Squeeze the spray gun trigger to flush water through the pump and wand
4. Disconnect the hose and drain the water from the pump by pulling the recoil start cord a few times (with the engine off)

Step 2: Add Fuel Stabilizer

For gas pressure washers:

1. Add fuel stabilizer to a full tank of fresh fuel
2. Run the engine for 5–10 minutes so treated fuel flows through the carburetor
3. This prevents the carburetor from clogging during storage — the #1 cause of spring no-start problems

If you prefer to drain the fuel completely, run the engine until it stops, then drain the carburetor bowl.

Step 3: Use Pump Saver (Critical Step)

Pump saver (also called pump protector or pump antifreeze) is a pressurized can of antifreeze and lubricant that you connect to the water inlet. It does three things:

1. Displaces water from the pump internals
2. Prevents freezing — the antifreeze lowers the freezing point of any remaining moisture
3. Lubricates the seals so they don't dry out and crack during months of storage

How to Use Pump Saver

1. Shake the can vigorously for 30 seconds
2. Screw the can onto the water inlet (where the garden hose connects)
3. Press the button on the can to inject the contents into the pump
4. Pull the recoil start cord 2–3 times to distribute the protectant through the pump
5. Remove the can and store it for next year

One can of pump saver costs about $10 and is the single most important thing you can do to protect your pressure washer during storage. Skipping this step is why most pumps fail after winter storage.

Step 4: Change the Engine Oil

For gas pressure washers, change the engine oil before storage:

1. Drain the old oil while the engine is warm
2. Refill with the oil specified in your manual
3. Old oil contains acids and moisture that corrode the engine during storage

If your pump has serviceable pump oil (check your manual — some axial cam pumps are sealed), change the pump oil too.

Step 5: Clean and Protect

1. Clean the pressure washer — wipe down the frame, pump, and engine. Remove dirt and chemical residue.
2. Clean or replace the air filter — a dirty filter left in place will harden during storage.
3. Inspect the hoses for cracks or wear. Replace damaged hoses before they burst under pressure next season.
4. Remove the spray tip and clean it with the included wire tool. Store the tips in a dry place.

Step 6: Store Properly

1. Store in a dry, frost-free location — a garage or shed is fine; outside is not.
2. Store upright — don't lay the pressure washer on its side, which can cause oil to flow where it shouldn't.
3. Coil the hose loosely without kinks. A kinked hose develops weak spots that burst under pressure.
4. Disconnect the spray gun and wand and store them separately.
5. If you must store outside, use a fitted cover — not a tarp, which traps moisture.

For Electric Pressure Washers

Electric pressure washers need less winterization, but still:

1. Flush the pump with clean water
2. Use pump saver — yes, electric pressure washers need it too. The pump is the same type and can freeze and crack.
3. Drain all water from the pump and hose
4. Store in a frost-free location
5. Coil the power cord loosely and store it where mice can't chew it

Spring Start-Up After Winterizing

If you winterized properly, spring start-up is simple:

1. Check the oil (gas models)
2. Fill with fresh fuel (don't use last year's stabilized fuel if it smells stale)
3. Connect the garden hose and turn on the water
4. Squeeze the trigger to let water flow through the pump before starting the engine (never run a pressure washer pump dry)
5. Start the engine and let it warm up for 30 seconds
6. Test the pressure — it should be at full pressure immediately

If the pressure is low or the engine surges, check for a clogged nozzle, dirty inlet screen, or stale fuel.

The Bottom Line

Pressure washer winterization comes down to three things: flush the water, stabilize the fuel, and use pump saver. The pump saver is the step most people skip — and it's the one that prevents the most expensive repair. Spend $10 and 15 minutes now to save a $100+ pump replacement in the spring.