How Do I Winterize My Pressure Washer?

Yes — every pressure washer, electric or gas, must be winterized before it sits through freezing weather. Water left inside the pump freezes, expands about 9%, and cracks seals, valves, and the pump housing itself. A new pump head can cost $150–$300, often more than a budget machine is worth. The whole job takes 20–30 minutes: disconnect everything, drain all the water out, run pump-saver (non-toxic RV antifreeze) through the pump until it exits the outlet, and store it dry and covered. For gas models, add fuel stabilizer to the tank and run it for 2 minutes so the carburetor doesn’t gum up.

Why freezing destroys pumps

A pressure washer pump is a sealed chamber full of precisely fitted parts — pistons, check valves, and rubber O-ring seals — with almost no room for expansion. When trapped water freezes, it expands roughly 9% in volume and has to push something out of the way. That “something” is usually a seal, a check valve, or the aluminum pump housing itself.

The damage is rarely visible from outside. You store the machine in November, everything looks fine. In spring you hook it up and water sprays sideways out of the pump, pressure is gone, or the motor screams with no water coming out. Common freeze damage:

• Cracked pump housing. Hairline cracks that leak under pressure. A replacement pump for a $200–$300 unit can cost $150–$250 plus labor — close enough to replacement that most people just buy a new machine.
• Blown seals and O-rings. Seals pushed out of shape or split by expanding ice cause chronic low pressure.
• Stuck or broken check valves. Valves jam open or shut so the pump can’t build pressure or prime.
• Cracked hoses and fittings. Water trapped in the high-pressure hose, gun, or quick-connects can split them too.

The worst part: damage accumulates. A pump can survive one marginal freeze and die the second winter. The fix is cheap — a $8–$15 bottle of pump saver — and takes less time than a trip to the store for a new machine.

Tools & materials

• Pump saver antifreeze (non-toxic) — purpose-made pump saver ($10–$15) or propylene-glycol RV antifreeze ($5–$9/gallon). Never automotive ethylene-glycol antifreeze — it’s toxic, corrodes pump seals, and contaminates anything you spray later.
• Fuel stabilizer (gas models only) — $6–$10 for a bottle that lasts years.
• Bucket and old towels/rags.
• An adjustable wrench or pliers for hose fittings.
• A dry, protected storage spot — garage, shed, or basement.

Step-by-step: winterize your pressure washer

1. Disconnect everything. Turn the machine off and disconnect the water supply. Remove the garden hose from the inlet, unthread the high-pressure hose from the pump outlet, and detach the gun, wand, and nozzles. Separate all quick-connects. Nothing should be attached to the pump — every connection is a place water hides.

2. Drain the hoses, gun, and wand. Hold each hose vertically or coil it so water runs out of both ends. Elevate one end and walk the length of the hose squeezing it toward the downhill end. Squeeze the gun trigger (with the nozzle removed) and shake the wand to clear water from the lance. Let them drip-dry while you work on the pump.

3. Flush and drain the pump. This is the step people skip and the step that matters most. Tip the machine so the inlet faces downward and rock it gently — a surprising amount of water will pour out. If you have an electric model, let gravity do the work for a few minutes. For a gas model, pull the recoil starter cord 4–6 times (with the fuel valve off and the engine off) — this cycles the pump pistons and pushes trapped water out of the chambers. Never run the pump dry for more than a few seconds; the seals need lubrication, which is what the next step provides.

4. Run pump saver through the pump. This is the money step. With the machine off:

• Thread the pump-saver can or a short funnel of RV antifreeze onto the water inlet (this is what pump-saver cans are designed to fit — most have a garden-hose thread).
• Press or pour until the pink liquid flows out of the pump outlet and any detergent tube. When you see pink antifreeze coming out, the water is displaced and the pump is protected.
• If using bulk RV antifreeze, pour it into the inlet with a funnel until it exits the outlet — you need only a cup or two.

Leave the antifreeze in the pump over winter. It lubricates the seals and pistons while it protects them, which is why pump saver beats plain draining. In spring, flush it out with plain water before first use — run the garden hose through the pump for a minute with the engine off.

5. Gas models: stabilize the fuel. Gasoline goes stale in 30–60 days. Unstabilized fuel gums up the carburetor — the #1 reason small engines won’t start in spring.

• Add fuel stabilizer to the tank at the dose on the bottle.
• Run the engine for 2 full minutes so treated fuel reaches the carburetor.
• Top off the tank (a full tank has less air, so less condensation forms inside).
• Alternatively, drain the tank and carburetor completely — but stabilization is easier and more reliable.

Check the oil level and engine manual for any end-of-season service (oil change, air filter). A machine that starts on the first pull in April is worth ten minutes now.

6. Clean and protect the outside. Wipe down the machine, coil the power cord (electric) or drain the detergent tank (if equipped). Lightly oil metal quick-connects and the pump inlet/outlet threads to prevent corrosion. Stuff a clean rag or cap into the inlet and outlet to keep spiders and dust out over winter — they love nesting in small openings.

7. Store it dry, covered, and uncoiled. Store the washer in a garage, shed, or basement — anywhere that stays above freezing is ideal, but a properly winterized pump handles a cold garage fine. Never store hoses tightly coiled or kinked — residual water pockets and stress cracks form at the bends. Loop hoses loosely in big, gentle coils off the floor. Cover the machine with a tarp or old sheet to keep dust off.

What this costs

The $12 bottle versus a $250 pump is the whole argument.

Safety warnings

• Never use automotive (ethylene glycol) antifreeze in the pump. It’s poisonous, it attacks pump seals, and residue will spray out of the machine next spring onto your driveway, pets, and plants. Only propylene-glycol products: pump saver or RV antifreeze.
• Don’t run a gas engine indoors while circulating stabilizer — carbon monoxide builds fast. Work in the garage with the door open or outside.
• Don’t run the pump dry for more than a few seconds without water or antifreeze. Dry seals overheat and score.
• Depressurize before disconnecting. Squeeze the trigger with the machine off after the last use — a pressurized hose coupling can spray hard enough to injure an eye.
• Dispose of old antifreeze properly — take leftovers to a household hazardous waste collection, not the storm drain.

Frequently asked questions

Can I just drain the pump and skip the antifreeze? Draining alone is better than nothing, but you’ll never get every pocket of water out by draining — check valves and low chambers hold water. Pump saver displaces what you can’t drain and lubricates the seals for storage. It’s $10. Do both.

Is RV antifreeze the same as pump saver? Close enough for homeowner use. Pump saver is essentially propylene-glycol RV antifreeze with added seal conditioners, packaged with a fitting that threads onto the pump inlet. Both are non-toxic. Use either — just never automotive antifreeze.

Do I need to winterize if I store it in a heated garage? If the space genuinely stays above freezing all winter, draining is enough — freezing can’t happen. But if there’s any doubt (an unheated attached garage in a cold snap, a power outage while you’re away), run pump saver. Belt and suspenders beats a cracked pump.

I forgot last winter and the pump leaks now. Is it done? Not necessarily — check the cheap failures first. Tighten all fittings, replace the O-rings at the hose connections (a $5 universal kit fixes most drip leaks), and confirm the leak is from the pump housing, not a connection. If the housing itself is cracked, price a replacement pump against a new machine before spending money.

How long does pump saver last? Unopened, several years on the shelf. Once installed in the pump, one winter season. In spring, flush it out with fresh water before the first wash — it rinses clean.

My electric washer says “self-priming” — does that matter? No, for winterizing. Self-priming just means the pump can pull water from a bucket instead of needing pressurized supply. Winterize it exactly the same way.

Prevention tips

• Winterize before the first freeze, not after — the first hard frost in October/November sneaks up. Pick a date and treat it like a deadline.
• After every use, squeeze the trigger with the machine off to depressurize and clear the gun.
• Store detergent tanks empty — dried chemical residue corrodes the detergent pickup and valve.
• Keep the machine and hoses off bare concrete floors over winter; concrete wicks moisture and accelerates corrosion on the frame.
• Mark the stabilizer date on the fuel tank with tape so you remember in spring whether the fuel is treated.

When to call a pro

Pressure washer repair is usually a small-engine shop job, not a DIY plumbing project. Call a shop for: a cracked pump housing (price the pump replacement against a new machine — on units under $250 it’s often not worth fixing), a gas engine that won’t start after proper stabilization and fresh fuel, internal leaks you can’t trace to a fitting, or any repair under warranty (opening the pump usually voids it). A tune-up or carburetor service typically runs $50–$100 and is money well spent on a quality machine. Keep the manual — pump part numbers are machine-specific, and having the model number ready saves the shop (and you) a lot of time.