Electric compact
2.0 orifice · 2,000 PSI
About 1.4 GPM. Matches a 1.4 GPM electric. A 3.0 tip here wants about 2.1 GPM.
Orifice + PSI
Pressure washer GPM chart
The number on the tip is gallons per minute at 4,000 PSI. At any other pressure the flow changes with the square root of PSI. Read the table to see what a hole passes — and which size fits the pump.
Most homeowners land here. A 3.0 tip at 3,000 PSI passes about 2.6 GPM,
which is why a 25030 set fits a 2.5 GPM gas washer. The same 3.0 tip at 2,000 PSI wants about
2.1 GPM — more than a 1.4 GPM electric can feed. That machine wants a 2.0.
Orifice + PSI → GPM
GPM ≈ orifice × √(PSI ÷ 4000). The orifice number is gallons per minute at 4,000 PSI.
Uses the tip’s hole and your stamped PSI — not the box art.
Approximate flow 2.6 GPM
If that number sits well above the GPM stamped on the pump, the hole is too big and pressure falls. Well below, and the unloader has to bypass.
Orifice and PSI decide the flow
The pump is rated to deliver a given GPM at a given PSI. The tip is the hole that lets it get there. Industry convention — the same one on the tip orifice chart — says the orifice number equals gallons per minute at 4,000 PSI. For any other pressure:
GPM = orifice × √(PSI ÷ 4000)
Example: a 3.0 orifice at 3,000 PSI → 3.0 × √(3000/4000) ≈ 2.6 GPM. A 2.0 orifice at 2,000 PSI → 2.0 × √(2000/4000) ≈ 1.4 GPM. A 4.0 orifice at 4,000 PSI is 4.0 GPM, because that is the pressure the number is defined at.
These are approximate flows from that equation. They are not a bench test of a particular machine, and they are not the splashy GPM printed on the box. Tips wear, unloaders limit pressure, and a pump’s stamped rating is one point on a curve.
Which tip size fits the machine
Find your stamped PSI column. Read down until the GPM is closest to the number stamped on the pump. That row is the orifice. Then pick the fan color on the tip size chart.
A hole that is too small makes the unloader chatter, the hose jump, and the seals work overtime. A hole that is too large dumps the pressure you paid for. If you already know GPM and want the hole directly, the orifice chart solves the inverse: orifice = GPM × √(4000 ÷ PSI).
Electric 1.4 GPM @ 2,000 PSI lines up with a 2.0 orifice (about 1.4 GPM on this chart).
A 4.0 “pro” tip on that machine is why it feels like a garden hose.
Approximate GPM by orifice and PSI
Start with the three common bands. The full table is below — on a phone, scroll sideways; the orifice column stays put.
Most homeowners
3.0 orifice · 3,000 PSI
About 2.6 GPM. Start with 25030 / 15030 / 40030 on a 2.5 GPM gas washer.
Prosumer gas
4.0 orifice · 4,000 PSI
About 4.0 GPM. A 3.0 tip on this pump passes 3.0 GPM and chatters the unloader.
Full chart: each cell is approximate GPM from the orifice equation above.
| Orifice \ PSI | 1,600 | 2,000 | 2,500 | 2,800 | 3,000 | 3,500 | 4,000 |
|---|---|---|---|---|---|---|---|
| 1.5 | 0.9 | 1.1 | 1.2 | 1.3 | 1.3 | 1.4 | 1.5 |
| 2.0 | 1.3 | 1.4 | 1.6 | 1.7 | 1.7 | 1.9 | 2.0 |
| 2.5 | 1.6 | 1.8 | 2.0 | 2.1 | 2.2 | 2.3 | 2.5 |
| 3.0 | 1.9 | 2.1 | 2.4 | 2.5 | 2.6 | 2.8 | 3.0 |
| 3.5 | 2.2 | 2.5 | 2.8 | 2.9 | 3.0 | 3.3 | 3.5 |
| 4.0 | 2.5 | 2.8 | 3.2 | 3.3 | 3.5 | 3.7 | 4.0 |
| 4.5 | 2.8 | 3.2 | 3.6 | 3.8 | 3.9 | 4.2 | 4.5 |
| 5.0 | 3.2 | 3.5 | 4.0 | 4.2 | 4.3 | 4.7 | 5.0 |
| 5.5 | 3.5 | 3.9 | 4.3 | 4.6 | 4.8 | 5.1 | 5.5 |
| 6.0 | 3.8 | 4.2 | 4.7 | 5.0 | 5.2 | 5.6 | 6.0 |
Foam cannons need flow as well as a tip. Under about 2 GPM the foam and soap guide is honest: you get a thin film, so use the soap tank. A surface cleaner has the same constraint — diameter is coverage, GPM is what spins the bar. See the surface cleaner matrix.
Tip sets already sized to these bands
The driveway kit uses a 3.0-orifice quick-connect pack for the homeowner-gas band. The car kit uses a 5-pack the listing rates at 2.5 GPM and 4,000 PSI — paint-safe fans only. Confirm the hole against your stamped numbers before you click either one.
Live Amazon links with tag nozzlekit-20. No invented ASINs or prices.
Homeowner-gas tips
Simpson Cleaning 80145 3600 PSI Universal Pressure Washer Nozzles, 1/4-Inch Quick Connect, Set of 5Orifice 3.0 — the homeowner-gas hole. At 3,000 PSI that hole passes about 2.6 GPM on the chart above. Colors: 0° red, 15° yellow, 25° green, 40° white, soap black.
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2.5 GPM tip set
Tool Daily pressure washer nozzle tipsThe car kit’s 5-pack. The listing is a 2.5 GPM, 4,000 PSI quick-connect set. On paint, white 40° and green 25° only — and even 25° wants distance.
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Foam cannon
Tool Daily Foam Cannon with 1/4 Inch Quick Connector, 1 LiterDwell tool once the chart says you have the flow. Wants roughly 2+ GPM to make real foam. Pump-safe soap only — bleach never goes in the bottle.
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