Wash bays, jetting and where the dirty water goes

17 October 2026

A wash bay collects everything a lorry brings home. Road grime, traffic film, diesel splash, mud from a building site delivery and, after a winter run, more salt than anyone would want near a gearbox. Most of it ends up in the channels and the silt trap, and over time the channels set hard, the gratings choke and the bay floods every time a unit goes through.

Pressure is a tool, not a cure-all

Controlled water jetting shifts deposits that a hose and a brush will not touch. On a yard that means compacted silt in drainage runs, hardened residue in wash bay channels, concrete splashes on hardstanding, and grease and grime on workshop floors and around equipment. Water jetting is also used for removing coatings and corrosion from steel before further work, although that is a different job from clearing a wash bay channel. The surface underneath still matters.

Jetting is still a judgement call. The wrong pressure or nozzle can damage a weak pipe, cut into soft concrete or drive dirt further into a joint. The person doing the work should ask what the surface is, how old it is and what condition you need it left in, and should say so when another method would suit better.

The water has to go somewhere

This is the part people forget. Every jetting job makes dirty water, often carrying oil, silt and whatever came off the surface. Some freight yard surface drains lead towards watercourses or soakaways, while others pass through interceptors. None should be treated as an automatic outlet for dirty jetting water. It needs controlling: contained, collected and taken away or sent where it is permitted to go. Jet vac tankers combine water jetting with vacuum recovery, allowing loosened deposits and dirty water to be collected during the work.

Think of it as the return leg. You would not plan a run with no thought for how the trailer gets home. High Pressure Jetting covers drain, equipment and surface jetting with controlled washwater and jet vac tanker work, with washwater management included in its description of the work.

Booking a crew into a live yard

Jetting units are not small, and the work throws spray and noise. Pick a time when the bay can be closed, move vehicles away from the area, and tell drivers and fitters where the hoses will run. If the jetting is preparation for a drain survey or repair, line the jobs up so the camera or repair crew follows on before the pipes silt up again.

Afterwards, put the wash bay channels and silt trap on a routine alongside the vehicle inspections. A crew called in once the bay is already flooding has more to remove, more water to take away and a yard full of vehicles to work around. Keeping a record of when channels and traps were last cleared also gives the workshop something useful to check when water starts standing in the bay again.