1. What size of trench is required for a vacuum sewer?

In general, the width of the trench will be dictated by the construction method employed. For example, if a trenching machine is available and the ground conditions allow, the trench may be only 100mm wider that the pipe diameter. Back hoe excavated trenches are typically 450mm in width.

It would of course be necessary to increase the width when using a trenching machine where man entry is required to make joints.

2. What depth of trench is needed?

Usual practice demands a depth of cover of about 900mm is needed under trafficked areas to withstand wheel loadings, and 500mm to 700mm under non trafficked areas.

3. What bed and surround material is used?

This will be dependant upon the local codes for the type of pipe material being used. For example in the UK, a bed of 100mm of granular fill with a cover to the crown of the pipe of a further 150mm of granular material is used. The vacuum main does not demand a different bedding than for a water main in a similar pipe material.

4. Is the use of marker/tracer tapes recommended with vacuum sewers?

We recommend this as being good practice.