Winterizing a Pressure Washer to Prevent Freeze Damage

Winter is coming, and while you fret over frozen pipes and a dead car battery, one expensive piece of gear tends to get forgotten in the corner of the shed. Your pressure washer really does not handle the cold.

Shove the machine into storage with water still sitting in the pump and you are gambling with its life. Water expands by roughly 9% as it freezes, and even a small amount trapped inside can crack the manifold or split a seal. Come spring, you could be looking at a leaking paperweight instead of a working cleaner.

The good news is that learning how to winterize a pressure washer is quick, cheap, and hard to get wrong. Below you will find the exact steps for both gas and electric machines, so yours fires up on the first pull next season.

Why You Must Winterize Your Pressure Washer

You must winterize a pressure washer because water left in the pump expands about 9% as it freezes and cracks the housing. Trap that water inside the rigid metal or plastic housing of your pump and something has to give. Usually it is the pump itself.

Beyond a cracked pump, winterizing heads off two more expensive problems:

1. Corrosion: Moisture left in the system breeds rust and mineral deposits that seize up the valves and check balls.
2. Fuel decay: On gas models, untreated gasoline starts going stale in about 30 days. Roughly 90% of the fuel sold at U.S. pumps is an ethanol blend that pulls in moisture and leaves a gummy varnish, clogging the carburetor so the engine will not start when the weather warms up.

Twenty minutes now saves you hundreds of dollars in repairs or a full replacement later.

How to Winterize a Gas Pressure Washer

Gas units call for a two-part approach, because you have to care for both the engine and the water pump. Grab your supplies and get to work.

What You Need

Gather these items before you start:

• Fuel stabilizer.
• Garden hose.
• Canned pump saver (antifreeze and lubricant).
• Bucket of clean water.
• Clean rags.

Step 1: Treat the Fuel System

You have two choices for the tank: drain it bone dry, or fill it with stabilized fuel. Most manufacturers prefer a full, treated tank so the gaskets do not dry out and condensation cannot form in the empty space. Oklahoma State University Extension recommends draining the fuel system when a small engine will sit unused for more than 60 days.

1. Add stabilizer: Pour fuel stabilizer into the tank at the ratio on the bottle, then top off with fresh gas. This step matters because gasoline begins breaking down in about 30 days, and the ethanol in most pump gas leaves a varnish that clogs the carburetor ⁽¹⁾.
2. Run the engine: Hook up your water supply (never run the pump dry) and start the engine. Let it run about two minutes so the treated fuel cycles all the way through the carburetor. Do this outdoors, since the CDC warns against running a gasoline powered pressure washer in an enclosed space or less than 20 feet from any window, door, or vent.
3. Shut it down: Turn off the engine and the water supply. Squeeze the spray gun trigger to bleed off any built-up pressure.

Step 2: Flush and Protect the Pump

With the engine sorted, get the water out of the pump and replace it with lubricant.

1. Flush detergent: If you used the soap tank recently, drop the detergent tube into a bucket of clean water and run the machine on low pressure for a minute to clear the chemical residue, which otherwise turns sticky and gums up the valves over winter.
2. Disconnect hoses: Remove the garden hose and the high-pressure hose. Drain the high-pressure hose, gun, and wand by holding them upright.
3. Purge the pump: With the engine off, give the recoil cord about six slow pulls to push the last of the water out of the pump before you add any oil.
4. Apply pump saver: Screw the nozzle of your pump saver can onto the water inlet, where the garden hose normally connects.
5. Fill the pump: Press the button on the can and pull the recoil cord slowly a couple more times (do not start the engine). Watch the outlet, and once white foam comes out, the pump is full of lubricant and protected. A dedicated pump saver like Simpson Pump Guard shields the internals down to about -25F ⁽²⁾ and keeps the seals from drying out, which plain antifreeze does not do as well.

How to Winterize an Electric Pressure Washer

Electric models are a little easier, since there is no carburetor to worry about. The catch is that their pumps are often plastic, so they can crack even faster than a metal pump when trapped water freezes.

What You Need

You won’t need much for this job:

• Bucket of warm water.
• Canned pump saver (essential here).
• Garden hose.
• Clean towel.

Step by Step Instructions

Follow this sequence to get your electric unit through the cold:

1. Clean the system: If your unit has an onboard detergent tank, fill it with hot water. Run the machine with the low-pressure nozzle to flush out any soap residue, which can turn sticky and clog the seals over winter.
2. Disconnect everything: Turn the machine off. Disconnect the garden hose and the high-pressure hose. Squeeze the gun trigger to drain the leftover water from the wand.
3. Attach pump saver: Screw the threaded nozzle of the pump saver can onto the machine’s water inlet.
4. Inject the fluid: Press the button on the can. Since you can’t pull a cord on an electric unit, just press until fluid or foam exits the water outlet. Some electric models let you switch the motor on briefly (one to two seconds) to help cycle the fluid, but check your manual first, as the pressure from the can is usually enough.
5. Wipe down: Dry off the exterior of the machine and coil the power cord neatly.

Can You Winterize Without Antifreeze?

Technically yes, but it is risky. Some owners use an air compressor to blow the water out of the system instead.

1. The method: You attach an air compressor fitting to the inlet and blow air through until no mist comes out the outlet.
2. The risk: This clears the water, but it does not lubricate the seals. Dry seals can crack or stick. And if you miss even a small pocket of water, it can still freeze and crack the manifold.

For the sake of a few dollars, a can of pump saver is the safer bet. It works as a lubricant and a preservative for the O-rings, which compressed air simply cannot do.

Where to Store Your Pressure Washer

Once the machine is prepped, where it spends winter is your last line of defense, and gas and electric units want different spots.

• Electric goes indoors: A heated basement or an attached garage that stays above freezing is the ideal home for an electric unit.
• Keep gas ventilated: Store a gas engine unit in a dry, well-ventilated spot such as a shed or detached garage, away from any pilot light, furnace, or water heater, since fuel vapor near an ignition source is a fire hazard. Keep it flat so oil and gas cannot leak into the combustion chamber.
• Cover it up: Use a tarp or a fitted pressure washer cover to keep dust out of the vents and shed moisture if the roof ever leaks.
• Detach the accessories: Store the gun, wand, hoses, and nozzles in a box indoors. These parts hold water easily, so a warm, dry closet keeps them from cracking.

FAQs

Don’t Let Winter Win

Nobody wants to add another chore to the list, but winterizing a pressure washer takes under 15 minutes. Weigh that against hauling a cracked machine to the dump in April, and the choice makes itself.

Gas or electric, the goal is the same: get the water out and get the lubricant in. Stabilize the fuel if the unit has an engine, run pump saver through the inlet until it foams, then tuck the machine somewhere dry and above freezing. Do it now, and you will be blasting spring pollen off the driveway while your neighbor waits on a repair.