Articles and Guides

Ultimate guide to buying a car pressure washer

09 Jul 2009

When you are looking to buy a pressure washer for your car, the main specification on display is the units of PSI. This means “Pound per Square Inch”. Generally more expensive the unit is the higher the rated PSI. It would seem then that the natural assumption is, the higher the PSI, the better the pressure washer? This is not the case for car cleaning. In fact the most important bit of information is not generally on open display.

The most important specification for consideration is the “water flow through rate”. The higher the water flow the better and generally the PSI should be between 90 and 120psi. More than this can cause damage to the car. PSI can be adjusted by simply stepping back from the car. Ideally though it is better to pre adjust the pressure washer for the job at hand and most commercial pressure washers allow you to adjust PSI.

Why is water flow through rate so important?

The simple way to explain this is. If I had a thimble of water and through it at you at a 100PSI it would be irritating. If however I through a bucket of water at you at 100PSI it would knock you clean off your feet. This is why PSI is not that important as it the weight of water that gives you the cleaning and dirt removal power. It’s also this flow of water that improves rinsing time. With a high water flow rate you can rinse soap off the car in a single pass thus saving time. This is obviously an important factor if you’re buying a pressure washer for a hand car wash site. Reduce time of a job your make more money.

How do you select Motor RPM?

This is also important. There are two typical motor types 1400rpm and 2800rpm. There are reason for each motor type and its important that you understand the difference and the benefits of each type so you can buy the right machine for you business. The simplistic way of looking at it is the lower the RPM the longer the motor will last and thus in the long term be better value for money due to lower maintenance bills. However there are other factors to consider. 2800rpm are suited only to mains water supply only. You need to make sure your mains water supply is capable of supplying water to your unit. Under feed machines can cause also sorts of damage to the pump and this type of damage is not covered by warranty. You can check water supply by time how long it takes to fill a 5L bucket for example. This will give you a good guide to your mains water feed. Also remember mains water feed can be altered by running a bath, washing machine, dish washer and flushing a toilet. All these aspect need to be considered when running from mains water to make sure you prolong the life of your pump or reduce the need for servicing. 1400rpm pumps will run from mains water but is also capable of sucking water from a tank or pond with the right filter on the suction pipe. Lot of valeting sites run there pressure washers for tanks which gravity feed the pressure washer this is possibly the best way to feed a pressure washer. The bigger pressure washers have a buffer tank which keep the flow of water just right and thus prolonging the life of the pump.

Kränzle Quadro 11/140TST

Mobile valeters often buy cheap pressure washers which last 1 year or less. This is often to do with the fact that the motor rating is not suited to sucking water from a tank. There are several things to consider for mobile valeting pressure washers.

1. most mobile valeter carry there own water supply so you need a pump running at 1400rpm
2. Most valeter also get there power from a generator. The generator chosen will determine the pressure washer you buy. Kranzle is the only companies we know of that offer a unit running at 1400rpm and has a connection load of 1.6kw and running load of 1Kw. This means a small generator producing 3kva of power is more than capable of running this unit. When you take the next step you will find you will need generator producing power of 6kw. Your chose here depends on what you will do with your unit and how quickly you want to work.
3. Water flow rate an ideal water flow is 10ltrs a minute. But if generator size needs to be smaller then the max you will get on 1400rpm motor is 7ltr per minute. This fine for mobile valeting work. But if you have the money go for the bigger generator and bigger pressure washer.

Mobile valeters should choose between these pressure washers

1. Kranzle K7 120 Pressure Washer
2. Kranzle K135
3. Kranzle K145T with Extras
4. Kranzle Profi 160 TST Auto with Extras
5. Kranzle Quadro 11 140TS with Extras

Hand car wash sites

Kranzle 160TST or Quadro 140TS are better machine as they have a buffer tank enabling perfect water feed to the pump.

When choosing a pressure washer think about the application you’re using it for. There are lots of different pressure washer designs to suit different applications and working styles. You need to think about water supply. Is it mains water or is it from a tank. What rinsing power do you need? For commercial use I recommend 10l per minute. However we regularly recommend the K7/120 to mobile valeters with a 7L pre minute flow (there are good reason for this). In reality provided the PSI is low i.e. between 90 to 120PSI the higher the water flow the better. Power supply is also important if your going to be using a generator you need to make sure the generator is powerful another to run it. The rule of thumb here is you need to double the Kw to get the right Kva generator. IE if you have a 1.6kw unit ideally you need a 3.2Kva generator. This is a general rule and there are other factor that may mean you can use a lower rated generator to run the tool but its worth sticking this rule of thumb that way you won’t make an expensive mistake. Hour of use is also important. Some units are designed to be used all day every day while some are not. You can use most commercial pressure washers all day every day but you will need to do servicing more frequently, this can be very costly so it better to get the right machine to work the hours you need it to. Think of its as holiday time for your pressure washer. Small unit doing the job of a big unit simply means the small unit will wear out quicker and need service more frequently to keep up the pace. Which means it would need more time off than a big unit and in the long run the big unit would work out much cheaper. Choosing the RPM simply 2800rpm for mains only maximum 4hrs work per day depending on unit. 1400rpm mains water or tank feed motor will work 4 to 8hr per day depending on unit.

Remember the time a unit is working for, is only while its pump is switched on or you’re spraying water.

< Back to list