Watch most people clean something with a pressure washer, and you will see the same sequence. Squirt some detergent on at full pressure, then blast it straight back off again.
Then conclude the detergent was rubbish and go and buy a stronger one.
The detergent was fine, but you gave it four seconds to do a job that needed four minutes.
Cleaning is not one input. It is four, and pressure is only one of them.
The four inputs and how they trade against each other
Every cleaning job is a mixture of time, agitation, chemistry and temperature. Increase one, and you can reduce the others. Reduce one, and you have to make it up somewhere else.
Pressure is agitation. That is all it is.
It is the easiest input to add, and also the one that does the most damage when overused. An unfortunate combination.
Chemistry and time are free, or near enough, and they are the two that almost nobody uses well.
A cheap detergent given three minutes will beat an expensive one given five seconds. Every time.
So here is the method: let chemistry and time do as much as they can. Then use the least pressure that finishes the job.
Apply low, rinse high
Detergent needs to land on the surface and stay there. High pressure atomises it, throws most of it into the air and drives the rest straight off the panel.
Every decent machine has a low-pressure chemical route for this reason, and Kränzle machines give you two options. Use the chemical injection setting on a vario lance, or a dedicated foam lance with its own bottle.
The foam lance is the better tool for most work. It makes a thick foam that clings to vertical surfaces instead of running to the bottom in twenty seconds.
Clinging is the whole point, because foam that runs off is foam that is not working.
If your foam is thin and watery, check the gauze filter in the lance before you change product. A blocked or damaged gauze is the most common cause, and it is a couple of pounds to fix.
Dwell time is the free upgrade
This is the single biggest improvement available to most operators, and it costs nothing.
Apply the chemical, then walk away. Three to five minutes on most jobs. Longer on heavy contamination.
While you are waiting, apply chemical to the next panel, the next vehicle, the next section of wall. You are not standing idle; you are running two jobs in parallel. Work moves faster, not slower.
One rule you cannot break: never let it dry, because a detergent that dries on the surface stops working.
On paintwork, glass and alloy, it can stain for good. In sun or wind, work smaller sections and re-wet as needed.
Dilution: stronger is not better
Traffic film removers and degreasers come as concentrates, and the label gives a dilution range for a reason.
Running everything at maximum strength does three things. It costs you a great deal more money, and it raises the risk to paint, alloy, seals and trim.
And on many surfaces it does not clean faster, because the limiting factor was dwell time, not concentration.
Start at the weakest ratio on the label. Give it proper dwell. Only strengthen it if the result falls short, and only on the jobs that need it.
Keep a marked jug or a dosing bottle. Guessing by eye is how a 25 litre drum disappears in a fortnight.
Picking the right chemical for the dirt
Most cleaning problems are one of three types, and the fix is different for each.
Road film, general grime and grease. Use an alkaline traffic film remover, with Advanced TFR covering routine work.
Want the product to cling to vertical surfaces? Reach for a high foam version, and for heavy commercial contamination, step up to a super strength grade.
Brake dust and wheels. Use a dedicated wheel cleaner. Brake dust is iron particles bonded to the surface, and a general detergent will not shift it.
Wheels come first in the process, always, and they get their own brushes that never touch paint.
Biological growth on stone and render. This is where people reach for pressure and should not. A biocide applied and left will kill the growth at the root.
It then stays gone for a season or two instead of returning by spring. We have written about why the patio goes green again, and chemistry is most of the answer.
The working order that stops streaks
Order matters as much as product.
- Rinse first. Loose grit removed before anything else, so you are not dragging it around later
- Wheels and the dirtiest areas, with their own product and their own brushes
- Apply detergent bottom to top. Counterintuitive, but it stops clean runs from streaking down dirty panels and drying into marks
- Dwell. Three to five minutes, never to dryness
- Agitate if needed, with a brush or mitt, not with more pressure
- Rinse top to bottom, wide fan, sensible distance, letting gravity carry the dirt away from what you have already done
- Dry or finish before water spots form, particularly on glass and dark paint
For vehicle work, our detailing setup guide goes further into the equipment side.
Look after the machine afterwards
Detergent left sitting in the injection system is not neutral, and concentrated alkaline product attacks the seals over time.
Flush the chemical route with clean water at the end of the day. Run the injector on plain water for a minute or two. That clears the valve, the hose and the bottle.
Rinse and dry the foam bottle rather than leaving product in it between jobs. Check the chemical valve if suction becomes weak or intermittent.
Frequently asked questions
Why is my pressure washer not picking up detergent?
Check three things in order, starting with the lance, which must sit on the low pressure or chemical setting. Injection will not work at high pressure.
Next, check the gauze filter in the foam lance and the injector strainer for blockage. The chemical itself may also be too thick or too cold to draw, which thinning it a little fixes.
How long should you leave detergent on before rinsing?
Three to five minutes for most work. Longer for heavy grease or biological growth.
The limit is the point at which it starts to dry. Dried product stops cleaning, and it can stain paint, glass and alloy. Work in smaller sections in sun or wind.
Can I put detergent straight into the pressure washer pump?
No. Introduce detergent downstream of the pump, through an injector or a foam lance.
Running concentrate through the pump attacks the seals and valves, and it shortens the life of the machine.
What dilution should I use for TFR?
Start at the weakest ratio on the product label, and only strengthen it if the result falls short.
Overdosing costs money and raises the risk to paintwork, alloy and trim. It rarely cleans faster, because dwell time is the limiting factor rather than concentration.
Do I need a foam lance or is the built-in chemical function enough?
The built-in low-pressure chemical function works well for flat and horizontal surfaces. A foam lance makes a much thicker foam that clings to vertical panels and walls long enough to dwell.
On vehicles and buildings, the difference shows.
The bottom line
Pressure is the input everyone reaches for and the one that does the least useful work on its own.
Apply at low pressure and let it dwell. Use the weakest dilution that works, never let it dry, and rinse in the right order. Then flush the machine out at the end of the day.
Kränzle UK stocks the full Autoglym range alongside foam lances, injectors and spare gauzes. We can match the chemical to the job. Tell us what you are cleaning, and we will point you to the right drum.