Jet washing, power washing and pressure washing all name the same machine. What actually changes between one job and the next is flow, heat, and the nozzle on the end of the lance — and of those three, the number quoted on the box is the least important.
Three names, one machine
There is no meaningful distinction between the terms in Irish or British usage. Some of the trade reserves “power washing” for heated water and “pressure washing” for cold, but the usage is not consistent enough to rely on, and nobody should read a capability into which word a company happens to use.
The distinction that does matter is between pressure washing and soft washing. Soft washing applies cleaning chemistry at garden-hose pressure and lets it do the work — a different method with different applications, covered in soft washing versus pressure washing.
Bar, PSI and what they actually mean
Both units measure the same thing — the pressure at the nozzle. Bar is the metric unit and the one used on most equipment sold here; PSI is imperial and turns up in American specifications. One bar is a little over 14 PSI, so a 150-bar machine is roughly 2,200 PSI.
Very roughly, and it is the ranking rather than the figures that is worth remembering:
- A garden hose delivers a few bar. This is the working pressure for soft washing and for applying a treatment.
- Domestic machines sit around 100 to 140 bar. Fine for a car, a bin, a small patio.
- Professional cold-water machines run roughly 150 to 200 bar, and — more to the point — they sustain it continuously rather than in bursts.
- Above that is specialist territory: paint stripping, concrete preparation, industrial descaling. Nothing on a house needs it.
The important thing about these numbers is that on almost every domestic surface, more pressure is the wrong lever. Pressure is what cuts into tarmac, opens up sandstone, strips the face off a concrete roof tile and washes the sand out of block paving. Past a fairly low threshold, adding pressure adds damage rather than cleaning.
Why flow rate matters more
Flow is measured in litres per minute, and it is the specification most people never look at. It is also the one that decides how quickly a large area actually gets clean.
The distinction is straightforward once stated. Pressure cuts. Flow carries. Pressure breaks the bond between the dirt and the surface; volume of water lifts the loosened material and takes it away. On a driveway, most of the work is carrying — which is why a domestic machine with high pressure and low flow will clean a small patch impressively and take an entire weekend to do a drive.
A domestic machine might move 6 to 8 litres a minute. A professional one moves something closer to double that, and the practical difference over a large area is far greater than the difference in their pressure ratings would suggest.
The nozzle does more than the machine
The same washer behaves like a different tool depending on what is fitted to the lance, and this is where most avoidable damage comes from:
- A pencil or zero-degree jet concentrates everything into a point. It will cut timber, mark stone and strip a tile surface. There is very little legitimate use for one on a house.
- A fan jet spreads the same energy across a line — 15, 25 or 40 degrees. Wider means gentler and more even. Most domestic surfaces want 25 or 40.
- A rotary or turbo nozzle spins a pencil jet in a cone, so it covers area like a fan while hitting like a point. Effective and easy to damage a soft surface with.
- A flat surface cleaner — the wheeled disc that runs on the ground — holds two jets at a fixed height and spins them under a shroud. This is what prevents the tiger-striping a hand-held lance leaves on a large flat area, and it is what a driveway should be cleaned with. It also keeps the slurry contained instead of firing it up a wall.
- A soft-wash or low-pressure tip for applying chemistry, where the point is coverage and dwell time rather than force.
Distance is the other half of it. Halving the gap between nozzle and surface increases the force on that surface sharply, so a 40-degree nozzle held an inch away is more aggressive than a 15-degree one held at a sensible working distance. Damage on this kind of work is almost always caused by distance and dwell rather than by the rating of the machine.
What hot water actually changes
Heat dissolves what pressure has to break. On grease, chewing gum, oil and food traffic it makes a very large difference, and a heated machine will clean a commercial forecourt or a bin store in a fraction of the time a cold one needs.
On the ordinary domestic problem — moss, algae and general weathering — heat helps much less than people expect, because the limiting factor there is biological rather than adhesive. Killing the growth with the right treatment does more than heating the water does, which is why the standard approach to a green patio is chemistry first and pressure second. Where heat genuinely earns its place on domestic work is oil on a driveway.
It matters most on commercial premises, where the soiling is usually grease and traffic rather than growth.
Reading a quote or a specification
If you are comparing quotes rather than machines, the pressure figure is close to useless on its own. More telling:
- What is being fitted to the lance. A surface cleaner for the flat areas rather than a bare wand is the single clearest sign someone has done this before.
- Whether any chemical treatment is included, or whether the entire plan is pressure. On growth, chemistry-first means less pressure is needed and the result lasts longer.
- Whether block paving will be re-sanded afterwards, which is the question that most often separates two otherwise identical quotes — see power washing driveways and patios.
- What the plan is for the runoff — drains, planting, ponds and the neighbours.
- Whether the soft surfaces have been identified at all. Anyone quoting to jet wash resin-bound gravel or tarmac at full pressure has told you what you need to know.
How this is applied to particular surfaces is on driveway and patio cleaning and render and house washing.