straight forward health and safty advice 
Do not, under any circumstances enter any manhole, sewer, culvert or drain unless adequate safety arrangements have been made and they are in place The arrangements for working in confined spaces that are given on this website must be fully implemented. If there is any sign or suspicion of rat infestation, follow the precautions against Weil's disease that are given on this website. Take special care where chemical drain cleaners may have already been tried. Most are toxic and may cause burns.  If powered equipment and/or high-pressure washing equipment i s to be used, then follow the guidance given on this website.   Make sure that all equipment is thoroughly cleaned and disinfected after it has been used.
Work precautions