How to Clean Windshield Washer Reservoir | Restore Clear Spray

For the full breakdown, see our best Universal Windshield Washer Reservoir guide.

A washer reservoir that hasn’t been touched in years collects sediment, hard-water scale, and slimy film that turns spray weak and streaky. One wrong approach — hot water or harsh chemicals — can crack the plastic tank or damage hoses.

Here’s the step order that actually clears the system.

Drain the Old Fluid First

Turn the vehicle off and let the engine cool completely before raising the hood. Locate the washer reservoir — it’s a translucent plastic tank with a cap marked by a windshield-and-wiper symbol.

Remove the cap, then either of these works for draining:

• Drain plug or hose: if the reservoir has a plug or accessible hose at the bottom, disconnect it and let the fluid empty into a container. Collect whatever comes out and dispose of it properly — old washer fluid, especially anything mixed with antifreeze, is toxic.
• Suction method: no drain plug means using a siphon, turkey baster, or shop vacuum to pull out as much fluid and settled sediment as possible.

One caution before pulling hoses: some vehicles use a metal clip or clamp that has to be released first — yanking the hose without loosening it can damage the fitting.

Rinse and Scrub the Tank Interior

With the reservoir empty, spray clean water directly into the tank using a garden hose. Keep flushing until the runoff runs clear and the calcium buildup or sediment washes out.

Stubborn deposits clinging to the walls need a gentle hand — scrub with a toothbrush or soft brush rather than reaching for chemicals. The safe rule across repair guides is simple: no hot water, no harsh cleaners, nothing that can degrade the plastic.

If the tank holds oily or greasy residue, repeated rinse-drain cycles beat solvents every time. Strong DIY recipes like bleach or drain cleaner show up in videos, but they risk damaging the plastic and are not backed by reliable repair sources.

Reconnect, Refill, and Test

Reattach any hoses and secure clamps or clips firmly. Refill with washer fluid to the fill line, or to full if no line exists — leave a little room for expansion rather than overfilling.

Test the washers and keep cycling them until the spray runs clear. If dirty or greasy fluid still comes through, the lines or nozzles may hold trapped crud; run more fluid through and watch the spray pattern.

Still weak spray after a clean reservoir? The problem may not be the tank at all. Clogged nozzles, blocked lines, a failing pump, or a clogged filter inside the reservoir can all mimic a dirty tank. Inspect the system end to end before assuming the reservoir is the culprit.

If the reservoir is badly cracked, leaking, or the pump inlet is packed with gunk that won’t rinse free, replacement beats endless cleaning.

What Not to Do

Four mistakes cause most cleaning failures:

• Overfilling — leave expansion room and seat the cap snugly to keep contaminants out.
• Hot water or harsh chemicals — both can warp or crack plastic parts.
• Ignoring the pump or filter — some reservoirs have a filter that clogs independently and only clears once the tank is removed.
• Pouring old fluid on the ground — collect it and dispose of it properly; used washer fluid can contain toxic antifreeze.

Wear gloves and eyewear when handling washer fluid or draining the tank. If the reservoir includes a low-fluid sensor or pump mounted on the tank, disconnecting those components may be necessary for a thorough clean.