A surface cleaner is the accessory that transforms patio and yard work- until it doesn't.
It crawls. It stops spinning halfway across, and it leaves faint stripes that only appear once the slabs dry.
The usual conclusion is that it is a bad attachment. Nine times out of ten it is a good attachment bolted to a machine that cannot supply it.
What a surface cleaner actually is
Strip away the housing, and it is very simple. A horizontal bar carrying two nozzles, mounted on a swivel, inside a skirt.
The nozzles point a little off vertical. Water leaving them pushes the bar round, the same principle as a garden sprinkler. The skirt contains the splash and holds the head at a consistent distance from the surface.
That last point is why it removes stripes. A lance held in a human hand varies its distance and angle, and every variation shows up on the slab.
A head running on a skirt does not vary at all, so the finish comes out even.
Flow is what makes it work, not pressure
Here is the bit that gets missed.
Your machine produces a fixed flow. That flow now has to do two jobs at once: spin the bar, and clean the surface. A hand lance only ever had to do the second.
Then consider area, because a hand lance concentrates everything into one narrow strip.
A 400mm surface cleaner covers a circle of roughly a third of a square metre. It does that in a single pass, at the same litres per minute.
Output per square metre falls off sharply. The only thing that offsets it is having enough flow in the first place.
So take a surface cleaner sized for a big commercial machine and bolt it onto a small domestic one. It will crawl round, leave dirt behind and stall as soon as it meets resistance.
The attachment is fine, but the supply is not.
Matching the head to the machine
The rule is short: bigger machines take bigger heads, smaller machines take smaller heads. There is no advantage in oversizing.
Domestic and lighter machines, such as the K 1050 range and the Quickly, need a compact head.
Our UFO Light 260mm matches this class of machine, and it clears ground at a proper rate rather than dawdling.
For professional machines with the flow to support it, the full size UFO covers much more per pass. The wheeled version is worth the difference on any large area.
Pushing an unwheeled head across forty square metres of block paving is genuine work.
If you are unsure which class your machine falls into, send us the model number rather than guessing. A head that does not match is the most common accessory return we see.
Reading the symptoms
It crawls around or stops dead. Insufficient flow reaching the head. Either the head is too large, or the machine is not getting the water it needs.
Check the water supply before you blame the attachment, because a starved pump produces identical symptoms.
It cleans in visible arcs or patches. A partial blockage in one nozzle means the two jets are no longer doing equal work. Remove and check both.
It chatters and judders across the surface. Usually the skirt is catching on uneven ground, or a worn wheel. On rough flags, a slight lift and a slower pace help.
It leaves faint parallel stripes. You are walking too fast for the flow available, so consecutive passes are not overlapping enough. Slow down or overlap more.
Water sprays out sideways past the skirt. Either the skirt has torn, or you have set it too high. It is a containment part, and a torn one turns a tidy job into a mess.
It has become noisy and leaks from the centre. The swivel seal has worn, which is a serviceable part rather than the end of the attachment.
Setting it up properly
Sweep first. Grit and loose stone jam under the skirt and score the surface. Two minutes with a broom saves a great deal of aggravation.
Pre-treat the surface. Apply a detergent or biocide and let it dwell before you start.
The surface cleaner then rinses lifted dirt away rather than tearing bonded growth off by force. That is faster and far gentler on the slabs.
Set the height with care. Too high and you lose pressure at the surface and spray sideways. Too low and the skirt drags, and the nozzles risk touching.
Most heads are adjustable, so spend a minute getting it right on each new surface.
Overlap every pass by about a third. Not a tenth. The edges of the circle deliver less energy than the middle, and a third of a head stops that showing.
Walk at a steady, unhurried pace. Speed is where most striping comes from, and the machine sets the pace, not you.
Do the edges afterwards with a lance, at a matched distance. That keeps the perimeter from ending up a different shade from the middle.
Looking after it
A surface cleaner has three consumable parts, and all three are cheap.
The nozzles wear like any other nozzle. When cleaning slows down and pressure is fine elsewhere, this is usually why, so replace both together, never one.
The swivel seal is the part that leaks in the end, and replacing it restores the attachment to new.
The skirt or brush strip wears against the ground, so replace it when containment starts to fail.
Rinse the head through with clean water after use, above all if you have been running detergent. Store it off the ground so the nozzles are not sitting in grit.
Frequently asked questions
Why is my surface cleaner not spinning?
Almost always insufficient flow. The head may be too large for the machine's output. Or a narrow hose, a blocked inlet filter or a poor tap may be starving the machine.
Check the water supply first, then check both nozzles for partial blockage. An unbalanced pair will also slow or stop the bar.
What size surface cleaner do I need for my pressure washer?
Match the head to the machine's flow rate rather than its pressure. Domestic and compact machines need a smaller head, typically around 260mm.
Professional machines with higher flow can drive a full-size head, and oversizing gives worse results rather than better coverage.
Why is my surface cleaner leaving stripes?
Usually walking pace and overlap, so slow down and overlap each pass by about a third of the head width.
Do the stripes appear in regular arcs rather than lines? Then one nozzle has a partial blockage, and the two jets no longer balance.
Can I use a surface cleaner on block paving?
Yes, with care: use a moderate setting and keep the head moving.
Expect to re-sand the joints afterwards, because any effective cleaning lifts some kiln-dried sand. Pre-treating with a biocide cuts the force you need.
Do surface cleaners work better than a lance?
For flat areas, by a long way, because they hold a constant height and angle. That is what removes the striping a hand-held lance almost always leaves.
They also cover far more ground per pass. For edges, vertical surfaces and detail work, you still need a lance.
The bottom line
A surface cleaner is not a power upgrade. It spreads the flow you already have across more ground, and it spreads it evenly.
Match the head to your machine, feed that machine well, pre-treat the surface and overlap by a third. Keep your pace steady, and the stripes disappear, and the job takes a fraction of the time.
Kränzle UK stocks surface cleaners for every machine in the range, along with replacement nozzles, seals and skirts. Tell us your model, and we will size the head right the first time.