High Pressure Jetting Methods and Applications

The deposit and the surface beneath it

Silt, mineral scale, roots, coatings and process residues behave differently. Loose sediment may need mobilisation and recovery, while a strongly attached deposit can require a different approach. An unknown residue needs identification before assumptions are made about how it will respond to water.

The pipe or surface must be considered alongside the deposit. Material, wall condition, linings, coatings, earlier repairs and vulnerable fittings can limit the available method. A clean-looking surface is not a useful result if the underlying asset has been damaged.

A cleaning objective that can be checked

The intended result may be restored passage, removal of a particular deposit, access for an inspection or preparation for a later coating. Those are different objectives. The work description should make the required extent and finish clear enough to assess afterwards.

Before-and-after inspection can show the accessible condition, but it does not establish every hidden defect. For a drainage run, remaining sediment, open connections and visible pipe defects are relevant. For a prepared surface, the acceptance criteria come from the next operation and the asset specification.

Access and the work area

Pipe length and diameter, available openings, bends and the distance from the equipment affect how the jetting head can reach the deposit. A vessel has different access and isolation arrangements from an open pavement. The same material can therefore need a different cleaning setup in two installations.

Work on plant has to fit the maintenance arrangements for that plant. The HSE guidance on maintenance of work equipment explains the importance of planning and suitable isolation. Those controls are part of the job assessment rather than evidence that a particular cleaning technique is suitable.

Recovering what the water removes

Loosened material remains part of the job. Moving silt down a drain can leave it at the next restriction; washing contamination from a surface can transfer it into runoff. The recovery method therefore needs to be considered with the cleaning method.

The amount and character of the washwater affect containment, separation and the route for treatment or disposal. For sites in England, the Environment Agency pollution-prevention guidance explains how drainage routes and potentially contaminated water should be managed. Surface-water drains, foul sewers and controlled waters have different requirements. Cleaning a drain does not itself authorise a discharge into it.

Using the library for a particular deposit

The existing guides below separate mineral scale, concrete ingress, roots, silt and coating removal. They explain which asset information is useful and where cleaning needs to be distinguished from repair. A deposit name alone does not choose the equipment or establish a finished-work standard.

For example, root removal can expose an entry defect that needs a separate repair. Silt and grit recovery focuses on taking material out of the system. Keeping those objectives distinct makes the work easier to specify and the result easier to assess.

Detailed guides

• Mineral scale in pipes
• Concrete in drains
• Roots in drains
• Silt and grit in drainage systems
• Coating removal from steel