Pressure Washer Losing Pressure: How to Find the Cause
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The short answer
Test in this order: clean the nozzle with the tip wire, check that the garden hose supplies at least 5 gallons per minute, inspect the inlet screen for grit, then check the unloader valve. A pulsing wand is nearly always air or a partial clog, not a dead pump.
Nozzle Tip Cleaning Kit
The wire that fixes most low-pressure complaints in under a minute.
Low pressure feels like a broken machine, but the pump is the last thing to suspect. Pumps fail slowly and fail hard; nozzles and water supply fail suddenly, which is what you're actually experiencing.
Test the Water Supply First
Fill a 5-gallon bucket from your garden hose and time it. If it takes longer than 60 seconds, the machine cannot get the flow it needs and pressure will sag no matter what you do. Kinked hoses, partially open bibs, and long skinny hoses are the usual culprits.
Then the Nozzle
- Pull the nozzle and push the tip cleaning wire straight through it.
- Backflush it with water in the opposite direction of flow.
- Swap nozzles — if pressure returns with a different tip, the old one is worn or plugged.
- A worn nozzle orifice enlarges over time and drops pressure permanently. Replace the set; they are cheap.
Then Inlet Screen, Hose and Unloader
| Cause | Symptom | Fix |
|---|---|---|
| Clogged nozzle | Narrow, weak or fanning spray | Tip wire, backflush, replace |
| Low supply flow | Pressure sags after a few seconds | Shorter/wider hose, open bib fully |
| Dirty inlet screen | Pulsing, air in the stream | Pull and rinse the screen |
| Air in the system | Rhythmic pulsing | Trigger open 30 sec to purge |
| Worn unloader valve | Pressure spikes then drops | Rebuild kit or replace valve |
| Worn pump seals | Water leaking under the pump | Pump rebuild or replacement |
Frequently Asked Questions
- Why does my pressure washer pulse?
- Air on the inlet side or a partially clogged inlet screen. Open the trigger and let the machine run for 30 seconds to purge air, then pull and rinse the screen.
- How do I know if the unloader valve is bad?
- Pressure builds normally then collapses when you release and re-squeeze the trigger, or the machine runs at full pressure with the trigger closed. Both point at the unloader.
- Can a long garden hose reduce pressure?
- Yes. A 100-foot 1/2-inch hose can starve the pump. Use a 5/8-inch or 3/4-inch supply hose and keep it as short as practical.
The Gear We’d Buy
Everything referenced in this guide, in one place.
Nozzle Tip Cleaning Kit
Top pickThe wire that fixes most low-pressure complaints in under a minute.
Typically $8 - $15
Color-Coded Nozzle Set
Worn orifices lose pressure permanently — a fresh set restores it instantly.
Typically $12 - $25
Pump Inlet Filter Screens
Grit in the screen causes the pulsing people blame on the pump.
Typically $8 - $15
Lawn Tool Hub is reader-supported. We earn a commission from qualifying purchases made through links on this page, at no extra cost to you. Learn more.
Key Takeaways
- Time a 5-gallon fill to confirm supply flow first.
- Clean or replace the nozzle before touching the pump.
- Pulsing means air or a restricted inlet, not a dead pump.
- Suspect the unloader only after nozzle, supply and screen check out.
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Reviewed by
The Lawn Tool Hub Test Bench
We buy, borrow and break lawn tools on our own yards — clay in the back, sand-cut Bermuda in the front — and write down what actually changed the result.
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Top pick
Nozzle Tip Cleaning Kit