the old tank sealer can be easily removed by paint remover with methylene chloride
tap every hole, insert pant remover, cose the cup, agitate and let it inside for 5 minutes
the old sealer is destroyed, but needs the help of the free moving chain and screws to be removed
do not add water, only white spirit, because everything inside the tank will be stucked
repeat this procedure until all the old sealer is removed and then apply water under big pressure
