Please make sure that when you conduct the water test you do not get water into the air ports eg vent/vibrator exhaust port, inflatable seal port etc. you should have air pipes connected to these ports just long enough to come out of the water.
Extend the hopper with 4-5 bar air before lowering into water tank via fork truck. Make sure you do not put more than 1 bar into inflatable seal.
When test finished lower hygiene cover & allow to dry internally using air gun & cloths.