Closed Box Pressure Washing System
The Closed Box Pressure Washing System is currently the only asbestos roof cleaning method approved by the HSE and our approved contractors have the closed box pressure washing equipment necessary to complete this type of cleaning.
The Closed Box Pressure Washing system is essentially an industrial sized patio cleaner, with a spinning jet of water delivered from a high powered pressure washer.
The main reason that this system is favoured by the HSE is simply because the operator is remote from the washing equipment and lowers the cleaning head down the roof sheets from a static position on the ridge of the roof.
This means that the operator won’t be tempted to step off the working platform onto the roof surface.
However, there are some disadvantages to using a Closed Box pressure Washing system and these should be considered fully before deciding on which method you choose to clean your asbestos roof.
The Closed Box Pressure Washing System uses large quantities of water and delivers it to the roof very quickly. This can lead to significant water ingress through holes and cracks present in the roof.
Eaves and valley gutters can quickly become overwhelmed and are likely to flood, leading to water ingress and internal and external asbestos contamination due to overflowing.
The sheer size of the cleaning head can make cleaning roof sheet edges close in valleys and at the eaves, very difficult and lead to the contractor being tempted to clean the inaccessible areas with a jet wash lance. This practice is extremely dangerous and can lead to destruction of the roof sheets.
A competent contractor will make every effort to reduce the risks, but they cannot be eliminated.
Waste Water Filtration
All waste water from asbestos roof cleaning exercises must be filtered in order to prevent asbestos fibres being released into the water system.
The rainwater goods are generally diverted into a filter box that filters the water down to approximately 5 microns.
It is good practice to test waste water before and after it is filtered, as this will provide documented proof that best practices were followed during the asbestos roof cleaning exercise.
Note that because of the volume of water produced when using the Closed Box cleaning method, large filtration boxes are likely to be required than when using steam.
It is also impossible to filter the waste water that is overflowing from eaves gutters, which it invariably does when employing a Closed Box system.