Difflock Guide to Pressure Washers

• PART ONE: Guide to Pressure Washers
• PART TWO: Pressure Washing Vehicles

Pressure washers are incredibly versatile and effective cleaning tools. They can be used for vehicle cleaning, removing stains, moss and mildew from brickwork, driveways, paths, patios and even garden furniture. With the right attachment they can even be used for cleaning and unblocking drains!

For our purposes though, we want to focus on 4x4s and the importance of pressure washing thoroughly prior to carrying out maintenance or repair. This is because 4x4’s are especially good at attracting loads of clinging dirt, mud, oil and grease. This combination of muck is excellent at the following:

• Stopping you seeing and identifying vehicle components clearly
• Fouling the threads on nuts and bolts or simply stopping a spanner or socket from fitting over same
• Finding its way into bearings, oil ways and engines as you carry out work, once there its as good as a grinding paste promoting wear and tear.
• Finding its way into your ears, eyes (very hazardous), nose and mouth as well as contaminating your skin.
• Making nuts, bolts and other components very slippery and difficult to grip or keep a spanner on.

In fact the list goes on and the only answer in our opinion is to make sure you have removed all the muck before you start any work on your beloved 4x4.

Buyers guide

If you have used a garden hosepipe you will know that a sharp jet of water is better and quicker at shifting muck then a gentle sluicing. Pressure washers harness this principle by using a powerful electric motor to pump water (usually fed from a garden hose) to very high pressures. This produces a high speed, highly penetrating jet of water that is directed by a long handled lance at the object to be cleaned.

Pressure washers are also extremely efficient and use as little as 1/10 the volume of water used by an ordinary garden hose.

Pressures washers fall into two main categories:

Cold water pressure washers

These take water fed directly from the cold water mains supply and pump it out at high pressures (70 – 200 Bar or 1000 to 3000psi). On better quality machines the pressure can be varied to suit the work in hand and a siphon tube or reservoir permits the addition of special detergents to aid cleaning. They are excellent at removing organic matter, mud, dirt and all water-soluble compounds. They will also remove fats, oils and greases but work much better if degreasing compounds are worked into these non soluble compounds first (more on this later).

Hot water pressure washers and ‘steam’ cleaners

These work in the same way as their cold water counterparts but heat the water up (after pumping) to 100 - 140 C in an internal boiler. As well as requiring an electricity supply the ‘steam’ cleaner versions often require a liquid fuel such as heating oil or paraffin to heat the boiler. They are excellent at shifting very heavy deposits of oils and greases and tend to leave a drier surface afterwards. They are typically used on larger vehicles such as HGV’s and are considerably more expensive than cold-water cleaners.

Hot water pressure washers are also especially useful for stripping off old, hardened underseal and for this activity the hotter the output the better.

Because they can strip away non-soluble compounds without the need for a degreasing solution, they should only be used where the waste run off passes through a special oil/water separator.

For the vast majority of users, a cold-water pressure washer is more than adequate for home and workshop. There is, however a huge range available so these are the things to consider when parting with your cash:

Motor Power

Power is everything or so we are told, but this is not necessarily the case with pressure washers. Typically the power of a pressure washer is directly related to the power of its motor. The output power of the motor is measured in Kilowatts and can vary from 1.6 Kw for a small machine to around 2.5 Kw for a powerful, heavier duty version.

This motor power affects the flow of water out of the lance (measured in Litres per Hour) and the pressure at which it is pumped (measured in psi or Bar). It is the combination of this flow and pressure that determines the effectiveness and speed of the cleaning effect. By multiplying the two figures (Flow x Pressure) together you can get a better figure, (called the ‘work value’) for comparing machines than just looking at motor power alone. Remember though to check that you are comparing like figures with like, so if one manufacturer is quoting pressure in BAR but another is quoting it in PSI you will have to convert one to the other before multiplying out.

As you would expect the work value varies considerably and typical figures vary from 3,500 for small machines to around 7,500 for a powerful machine.

Better quality machines allow you to vary the output pressure and flow with an inbuilt control. On cheaper machines this can be achieved by varying the nozzle on the lance but this sacrifices more flow in order to achieve higher pressures, so cleaning will consequently take longer.

If you only require your machine for occasional vehicle cleaning (including engine, gearbox and axles) and then only for light oily residues, road spray and dirt then even the smallest machine will be adequate for your purposes. If however you coat your vehicle in thick mud, manure once a month or it has years of accumulated oil and grease on it then you really need a higher workrate, say from a middle range machine.

Really powerful, top of the range models are really only necessary if you are cleaning a heavily soiled vehicle on a daily or weekly basis. However, if you have a very large driveway, acres of patio, or large expanses of brickwork to clean, then buy the most powerful machine you can afford since these jobs really require very high work values. Yes, you might manage with a smaller machine but it will take hours and hours to produce effective results since you will be trying to clean these large surface areas with the very narrow, ‘pencil’ jet characteristic of smaller models.

It’s also worth saying a word about motor types. Better quality machines have induction motors. Unlike cheaper motors these do not have carbon brushes that wear down and have to be replaced so an induction motor is more reliable and well worth the extra cost.

Basic Features

Because the water is pumped out at a very high pressure it is fed to the lance using a special high-pressure hose. Generally speaking the longer this high-pressure hose is, the better, since it gives greater flexibility. Any effect of the extra hose length on output pressure is negligible for practical purposes. These high pressure hoses can be damaged by kinking and have to be carefully coiled so if your budget allows, look for machines with a built in hose drum that makes storage far more easy and convenient.

Smaller machines are hand portable and so should feature a convenient carrying handle as well as a strong case. The weight should be balanced too, so that when picked up by the handle the machine is comfortable to transport.

Trolley and wheel mounted versions are available too and these make moving the machine around so much easier, so again are worth the extra investment.

The lance at the end of the hose should have a locking trigger to reduce hand fatigue during prolonged use. It should also have a nozzle that can vary between high pressure ‘blast’ and low pressure ‘soak’ settings since the soak setting is necessary when applying detergents via the pressure washer itself.

Speaking of detergents, check that your machine can automatically mix a suitable detergent with the ‘outflowing’ water stream. Often an inbuilt tank or a small, pull out siphon tube with a filter on the end is used and dipped into the detergent container. Other washers use detergent pellets that are loaded into the machine. We prefer the tank or siphon tube variety since this allows greater choice in the selection of a suitable detergent, especially since these can be quite a high price (£10 for 5 litres is typical in the UK) unless you shop around.

Power leads and supplies

A good long power lead is an absolute must and in fact we recommend that leads are at least 5 metres in length. Sadly not all machines have long leads so even with new machines fit a long lead if necessary (you must use cable that is rated to carry a full 13 Amps at whatever length you select – ask the cable supplier if in doubt). Note that some machines have a built in cable winder and this may not permit simple lead replacement, so with these be doubly sure to get the longest lead you can.

When replacing short or damaged leads you may find that the machine case is held together with tamperproof screws so if you don’t already have a set of tamperproof screwdriver bits then buy a set now.

There is of course a good reason for needing a long power lead. Water and electricity don’t mix and pressure washers are especially good at directing jets of water over long distances. For this reason we always plug our machine in behind a partially closed door or window such that it is impossible for an inadvertent jet of water to hit the plug and socket. Be especially careful when using 13 Amp extension leads for extra reach when working outside. At the very least spray them with and the pressure washer plug with WD40, tape them up inside a polythene bag and place them on a raised surface well away from any area where puddles, splashes or ‘rivers’ of water will be.

You absolutely must use an RCD rated at 10mA trip current at all times in conjunction with any pressure washer. These can be purchased for around £20 in a variety of forms such as fixed socket, replacement plug or plug in socket. An RCD will automatically cut off the mains supply in a few thousandths of a second in the event that you or any stray water finds its way onto a live connection. If you don’t have one BUY ONE NOW and use it with all your power tools, it will probably save your life one day. You may already have an RCD fitted in your house consumer unit. Since a consumer unit RCD is usually rated to trip at 30mA or more, you should still buy and fit a 10mA version to your workshop, garage or individual tools. 10mA versions are more sensitive and hence offer more protection, they also offer belt and braces peace of mind if that 30mA unit doesn’t trip!

Accessories

Check that any machine you buy has its own wide range of additional accessories or at the very least is compatible with those from other manufacturers. Accessories are essential to getting the most from your investment in a good quality pressure washer. Here’s a brief summary of some of those available.

Variable Nozzle Lances

These come in a variety of forms and will produce fan, pencil, low pressure (for detergent application) and even rotating jets of water. They are very useful for cleaning different surfaces such as Vehicles, patios, walls etc. Typically the various nozzles allow you to clean faster but be careful when using pencil jets since these can severely damage vulnerable surfaces, even concrete.

Sandblaster kits

These use a combination of high pressure, water & sand to remove old paint, rust and cement from metallic & stone or masonry surfaces. Whilst messy, these Sandblasters do not produce the copious quantities of dust like air-powered blasters. However, ferrous surfaces rust very quickly after cleaning since the exposed, bare metal remains wet. Also, if you wet blast clean a small area of stonework or similar it will stand out like a sore thumb compared to the rest so a small ‘spot’ clean may turn into a large ‘wall’ renovation. In fact this is true even without sandblasting attachments since the high-pressure water jet alone will scour away a naturally aged surface leaving it looking very different from its surroundings.

Suction Hose and Filter

These are recommended for use when using an alternative water supply, such as a water butt, when mains is not available

Extension Lance 450mm

These are very useful for difficult to reach areas and are also safer for use on shaped surfaces where there is a risk of the jet being directed back towards the operator.

Extension Hoses

These are safer than running power extension cables and allow the water jet to be used further away from the washer. They are also useful for cleaning bigger vehicles without the need to constantly reposition the washer.

Drain cleaner kits

These are a must have if you are responsible for the drains on your land or have a Septic Tank. They use powerful jets of water to push the cleaning head along the drain. The jets have a scouring action, cleaning the drain walls and breaking up debris that is obstructing or blocking the drain. Check the length though, some are 7.5m long and some are 10m long, obviously the longer the better. Note that they fit on the end of the existing lance so you cannot reach further along the drain by using an Extension Hose.

Brush attachments

In all candour we’ve never been very impressed by these. They do make a better job of cleaning Vehicle bodywork but the brush head stunts the power of the jet. Another disadvantage is that a small piece of grit or similar, lodged in the brush, can really damage the paintwork.

Frankly, for vehicle bodywork, an ordinary garden hose with a brush attachment or even a sponge is just as good. They’re worth having if they come ‘free’ with the washer but otherwise you may be disappointed.

Detergents

What next?

Hopefully we’ve given you a very good idea of the types, accessories and power options available when buying a pressure washer. We would strongly advise that before you purchase, you make a list of everything you want the pressure washer to do, and the extra attachments you may require. You can then use this list to both select and compare various machines in order to decide the best match for both your requirement and your budget.