Jargon, decoded
Every term this category throws at a first-time buyer, one line each.
Buying a first pressure washer means reading listings written for people who already own one. Two measurements decide almost everything — PSI and GPM — and the rest of the vocabulary exists to describe pumps, fittings and attachments that either match your machine or do not. None of it is complicated. It is just unexplained.
Here is the whole vocabulary in alphabetical order, defined in plain language, with a link to the page that goes into each properly. If you read only three entries, read GPM, cleaning units and nozzle colors: between them they account for most of the regretted purchases in this category.
Already know the words and just want a machine? Start here walks the decision in five steps.
- Axial pump
- The direct-drive pump fitted to almost every homeowner machine, electric or gas. It is compact and cheap to build, it spins at motor or engine speed, and on most consumer units it is sealed rather than serviceable. Expect it to wear sooner than a belt-driven or triplex pump, and to be replaced rather than rebuilt. See types of pressure washers.
- Black tip (soap nozzle)
- The widest nozzle in the box, roughly 65 degrees, and the only one that will draw detergent through the machine. Fitting any other tip is the single most common reason soap does not come out. See the nozzle color chart.
- Certified PSI vs max PSI
- Max PSI is measured at the instant the trigger closes and no water is moving. Certified PSI is the pressure the machine holds while it is actually cleaning. A listing quoting an honest certified figure looks weaker on a spec sheet than one quoting a max figure for the same machine, which is why this site does not rank by the headline number. See how we pick.
- Cleaning units (CU)
- PSI multiplied by GPM. It is the closest single number to how fast a machine will actually clean, because pressure breaks dirt loose and flow carries it away. 1,800 PSI at 2.0 GPM (3,600 CU) out-cleans 2,000 PSI at 1.2 GPM (2,400 CU) despite the lower headline figure. See PSI vs GPM explained.
- Detergent tank
- The onboard soap reservoir on most electric machines. It feeds at low pressure only, so it does nothing unless the soap tip is fitted. Two tanks is a real convenience: house wash stays in one, car soap in the other.
- Downstream injector
- The valve that pulls detergent into the water after the pump, at low pressure, so the chemical never passes through the pump seals. It only draws once the pressure drops, which is why it needs the soap tip. See how soap injectors work.
- Dwell time
- The minutes a detergent is left on a surface before rinsing. It is the part of the job that does most of the cleaning people credit to pressure, and it costs nothing. See soft wash vs pressure wash.
- Extension wand
- A rigid or telescoping lance that adds reach, so a second story, soffits or gutters can be washed from the ground instead of from a ladder. Length costs you control, so buy the shortest one that reaches. See extension wands.
- Foam cannon
- A bottle and brass orifice that fits the high-pressure wand and turns soap into thick clinging foam. It has a minimum flow requirement, which is why a cannon that works on a gas machine can dribble on a low-flow electric. See best foam cannons.
- Foam gun
- The garden-hose version of the same idea. No pressure washer needed, and far thinner foam. See foam cannon vs foam gun.
- GPM (gallons per minute)
- How much water the machine moves. Flow is what carries loosened dirt off the surface, and it decides whether an attachment such as a surface cleaner will spin at all. It matters more than most first-time buyers expect and it is advertised far more quietly than PSI.
- Inlet filter
- The small screen where the garden hose attaches. It catches the grit that would otherwise reach the pump, it costs almost nothing, and a blocked one is a common cause of weak pressure. Check it before suspecting anything expensive. See pressure washer won’t build pressure.
- M22 (14mm and 15mm)
- The 22mm threaded fitting used for hoses and guns on most homeowner machines. It comes in two internal sizes, 14mm and 15mm, which look identical and will not seal against each other. Measure before ordering a hose. See the connector guide.
- Nozzle colors
- Red 0°, yellow 15°, green 25°, white 40°, black soap. A pressure washer has no power dial — the tip is the setting. Green for concrete, white for everything else, black for soap, and most people never need the other two. See the full chart.
- Nozzle flow rating (orifice size)
- Every tip has an orifice sized for a particular flow rate, usually printed on the tip or the packet. A tip rated for more GPM than your machine delivers loses pressure; one rated for less over-works the pump. Match the rating to the GPM on your machine’s label.
- Pressure washer vs power washer
- A power washer heats the water; a pressure washer does not. Nearly everything sold to homeowners is a pressure washer regardless of what the box says. See the full comparison.
- PSI (pounds per square inch)
- The force of the water. Pressure breaks the bond between dirt and the surface, and too much of it is how people carve lines into decking and drive water behind siding. More is not better; enough is better. See what PSI do I need.
- Pump oil
- Serviceable pumps, mostly on better gas machines, have an oil fill and either a dipstick or a sight glass. Sealed consumer pumps have neither and are not meant to be topped up. See the pump oil guide.
- Quick connect (1/4-inch)
- The push-and-click collar fitting that nearly every spray tip and accessory uses. If your wand is M22 threaded instead, a few dollars of adapter converts it and opens up the whole accessory aisle. See the connector guide.
- Soft washing
- Cleaning with detergent and dwell time at low pressure instead of with force. It is the correct method for siding, painted wood and anything water can get behind. See soft wash vs pressure wash.
- Starved supply
- A machine cannot use more water than the tap gives it. A kinked hose, a half-open spigot or a long narrow supply line causes surging and weak pressure that looks exactly like a failing pump. Rule it out first.
- Surface cleaner
- A flat circular housing with two or three jets on a spinning bar underneath. It cleans a driveway in a fraction of the time and leaves no wand stripes, and it has a minimum GPM below which it will not spin properly. See will one work on my machine.
- Tool only
- A listing that ships the machine without the hose, gun, wand or tips. The price looks competitive and the real cost is not. Read the included-items list before comparing two numbers.
- Total Stop System (TSS)
- The pump runs only while the trigger is held, instead of idling continuously. It is quieter, it draws less power and it reduces pump wear, and it is standard on most electric machines worth buying.
- Triplex pump
- A three-piston pump, usually belt- or gear-driven, found on better gas and commercial machines. It runs cooler, lasts far longer and can be rebuilt. It is also a large part of why a contractor-grade unit costs what it does.
- Turbo nozzle (rotary nozzle)
- A 0° jet spun in a cone, so you get zero-degree intensity across a 25-degree path. It is the right answer for stubborn concrete and the wrong answer for anything softer. See best turbo nozzles.
- Unloader valve
- The valve that diverts water back through the pump when the trigger is released. A sticking unloader shows up as pressure that pulses or will not build, and it is one of the handful of things worth checking before assuming the pump is finished. See won’t build pressure.
- Winterizing
- Draining the pump and running pump antifreeze through it before the first freeze. Water left in a pump expands and cracks the head, and it is the most common way a perfectly good machine dies over one winter. See how to winterize.
A term we have missed?
If a page on this site uses a word that is not defined here, that is a gap worth fixing. Send it over on the contact page and it gets added.