straight forward health and safty advice 
A high-pressure jet of water can cause serious damage to the human body It is therefore essential that anyone using this type of equipment, uses the appropriate personal protective equipment.  If the equipment is electrically operated, the damp and wet conditions resulting from its use can be dangerous. To reduce the risk of electric shock use an RCD (Residual Current-operated Device). Check the equipment before you use it. Look at  that the cable and plug to make sure that they are not damaged in any way. Do not use the pressure washer if it has a damaged cable or plug. Do not tamper with electrical connections - a competent electrician must carry out any electrical repair work that is required. Pay particular attention to the hoses and if there is any sign of excessive wear, do not use them. Very high-pressure washers (135 bar [2000 psi] and above) must not be used off ladders or steps - a stable working platform is essential. When using a pressure washer make sure that: hoses are handled with care and not trailed over sharp edges or placed where they may be damaged. the spray is always directed away from people, or anything else that could be damaged by it; the spray is not directed at or near anything electrical. - even if it is isolated from its power supply - as water penetration may cause problems when the power is restored; the unit is not left running unless the lance is actually in use – it will cause the pump to overheat; hoses are coiled up neatly when they are not in use; in the winter months, the washer is protected from frost.
Work precautions