How the pressure washer nozzle chart works
Two things decide what a tip does on your washer, and the color is only one of them.
The color tells you the spray angle. Simpson and Alkota both print red as 0 degrees, yellow as 15, green as 25 and white as 40. Generac calls the same four Blast, Strip, Clean and Wash. Black is the soap tip. We looked for a published standard behind the code and couldn't find one. Treat it as a habit the makers share, and trust the degrees stamped on the tip over its color.
The stamped number tells you the size. On Spraying Systems' tips the first two digits are the angle and the rest is the size: 2504 is 25 degrees, size 4.0, and 40045 is 40 degrees, size 4.5. The same maker sells a 0-degree and a 25-degree tip of size 04 and rates them at exactly the same flow. The angle spreads the water. The size decides how much gets through.
The size number is the tip's flow in gallons per minute at 4,000 PSI. That's Cat Pumps' definition, and General Pump's chart is built the same way. So the two figures on your washer's label turn into a size with one line: size = GPM x √(4,000 / PSI). At 3,000 PSI and 2.5 GPM that's 2.89.
The chart uses half sizes, so the page shows the two either side of 2.89 and what each does at your 2.5 GPM. Size 3.0 gives about 2,778 PSI, a little under your rated 3,000. Size 2.5 needs about 4,000 PSI to push the same water, a third more than the washer is rated for. Alkota warns that with a tip that's too small, the water ends up "bypassing into the pressure unloader valve", and that wears the valve's seat. So the size up gets the big number.
Those pressure figures assume your full flow reaches the tip. Bypass water and hose losses can lower the pressure. Cat Pumps' troubleshooting guidance, as of October 8, 2026, says to allow about 5 to 10% for bypass flow when you size a nozzle, and the page doesn't take that off the flow you type.
Bar and liters per minute are converted first, with NIST's factors: 1 bar is 100 kilopascals, 1 PSI is 6.894757 kilopascals, and a US gallon is 3.785411784 liters. The page compares in exact arithmetic, so a washer that lands exactly on a size, like 2.1 GPM at 1,440 PSI on size 3.5, gets that size and not the next one up.
Who this is for
You own a pressure washer and a handful of colored tips. Maybe one went missing in the grass, or the new washer came with tips and no explanation, or the replacement set in your cart is sold by a number you've never seen. You want to know which tip does what, and which size belongs on your machine. If you know the colors already and only want the size, type the two figures off the label and skip the rest.
Homeowner questions about pressure washer nozzles
What do the colors on pressure washer nozzles mean?
The angle of the spray. Simpson and Alkota both print red as 0 degrees, yellow 15, green 25 and white 40, and black is the low-pressure soap tip. Red is the narrow one people call the strongest. Alkota calls it "the most aggressive of all tips", and Simpson warns its force "will actually penetrate soft materials or surfaces". We never mark it for a job, whatever you're washing.
Are pressure washer nozzle colors universal?
Not by any standard we could find. It's a habit Simpson, Alkota and Generac share, not a rule every set has to follow. The degrees stamped on the tip settle it. And no color tells you the size: two green tips of different sizes can behave very differently on the same washer.
What do the numbers on pressure washer tips mean?
The first two digits are the angle and the rest is the size. On Spraying Systems' tips 2504 is a 25-degree tip, size 4.0, and 1503 is 15 degrees, size 3.0. The size is the tip's flow in GPM at 4,000 PSI, so a size 4.0 tip passes 4 gallons a minute at 4,000 PSI and about 3.46 at 3,000. With your washer's two figures typed in, open "Check a tip you have or a surface limit" and type the number off your tip. The page says what that tip does on your washer.
What size nozzle do I need for a 3000 PSI pressure washer?
It depends on the flow, the other figure on the label. At 3,000 PSI and 2.5 GPM the size works out to 2.89, so the sizes either side are 3.0 and 2.5. At 2.3 GPM it's 2.66, and at 2.8 GPM it's 3.23. So two washers with the same PSI can need different tips. Type your own two figures and the page does the same sum for your washer, with the pressure at each size it shows.
Max PSI or rated PSI: which one do I use?
Rated, if the label or the manual gives it. That's the pair the washer works at. The box is busy selling the washer; the label just describes it. A max pair off the box still gives a size, and if you pick "Box (max)" the page tags it "Max figures, not a working pair". The two can point at different tips: say the box reads 2,000 PSI and 2.0 GPM and the label reads 1,500 PSI and 1.4 GPM. The first pair works out to 2.83, the second to 2.29, so the upper size changes from 3.0 to 2.5.
Which pressure washer nozzle for a car?
The makers don't agree. Simpson says to use only the white 40-degree tip or the black soap tip on a car, because a narrower pattern "may damage the paint". Generac lists cars under its white Wash tip. Alkota names its 25-degree tip for "houses, boats, and autos". Pick "Car, truck or boat" and "Quick-connect" in the form, and all three makers show up beside the rows they name.
What nozzle for house siding, a deck or concrete?
For siding, Simpson says white for most materials, Generac lists home siding under green, and Alkota names both: 25 degrees for houses, 40 for house siding. For a wood deck, Generac and Alkota both name green. For concrete, Generac names yellow for stains on driveways and green for driveways and sidewalks. If the deck or siding maker prints a top pressure, type it under "Check a tip you have or a surface limit".
What color is the soap nozzle?
Black, on Simpson and Generac washers. It's the low-pressure tip, and that's the point: Simpson says "High-pressure nozzles will not allow the soap injection valve to open", so red, yellow, green and white won't pull soap. Simpson's order is soap on first with black, then a higher-pressure tip to clean and rinse.
Do pressure washer nozzles wear out?
They do. Alkota's rule of thumb is to replace a tip once you see a 10 to 15% drop in pressure from new, which takes a gauge to spot. A clogged tip drops pressure too, and Alkota clears those with an automotive pick or a nozzle cleaning tool. Buy the replacement by its stamped number, not by its color.
Pressure washer tips chart: what the colors and numbers mean
A tips chart has two questions to answer, and they're easy to mix up. The color tells you the angle of the spray. The number tells you the size, and the size is what has to match your washer.
The whole job is short. Read the rated PSI and GPM off the washer's label, not the max on the box. Work out GPM x √(4,000 / PSI), or let the form do it. The half size just above the result keeps you at or under the rated pressure; the half size below asks the pump for more. A listing that says a set handles up to 4,000 PSI is telling you what the tip can take, not what size it is.
Two green tips from two different sets can be two different sizes. Check the stamped number before either one goes on the wand.
Sources and last checked
- Nozzle size number and formulas: Cat Pumps, Nozzles product page and Pumps & Accessories Catalog 2024 (page 38); General Pump, Nozzle Chart (2021). The size chart on this page is computed from the definition, not copied from either chart.
- Bypass flow: Cat Pumps, troubleshooting guidance.
- Stamped numbers: Spraying Systems Co., WashJet quick-connect product pages QCIMEG-40045, QCIMEG-40035, QCIMEG-2504, QCMEG-2504, QCIMEG-1503 and QCMEG-0004.
- Colors, angles and uses: Simpson, FAQ and "Choosing the Proper Nozzle for the Task at Hand"; Alkota, "Do You Have the Right Pressure Washer Spray Nozzles?"; Generac power washer owner's manuals G0069240 and G0088940.
- Safety: CDC, "Pressure Washer Safety".
- Units: NIST Handbook 44 (2026), Appendix C; NIST Special Publication 811, Appendix B.8.
- Last checked: October 8, 2026 (datasets version 2026-10-07; Generac quote-check version 2026-10-02).
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