Do not carry out any internal maintenance on portable toilet units without the correct level of PPE. This includes gloves and glasses. Also be aware of hygiene risks, ensure you wash hands thoroughly after use.
If the toilet won't flush properly, lift the lid on the waste tank.
You will see a 1" pipe with a plastic mesh bag hanging from the gusher pump. If it is fastened to the pipe by a jubilee clip.
Occasionally, the pipe assembly will become loose. Affix this by pushing the pipe and the bag on to the underside of the pump.
If the pipe is still fixed in place, check for splits. If a split is discovered a new pipe and mesh bag will have to be ordered/supplied.
Less common - If the pipe and bag are in good working order, check below the gusher pump for the condition of the black circular tubular diaphragm. If this is damaged, a Tardis engineer will be required to repair it.
Less commonly, with heavy use, two other issues occur. The toilet paper can cause the filter to become blocked. One sign of this is the flush handle becoming stiff to operate. If this happens, you will need to call a Tardis engineer to repair the problem.
If the flush handle has been operated aggressively, the mechanism may snap. The flush handle will move around with no resistance and the flush will not operate. In this instance, you will also require an engineer to repair it.
Very occasionally, the nozzle shown can become blocked. The best solution if this happens, is to clear it with a jet wash lance.