Wet filters are used to hold larger object in the vacuum tank. In another words, to keep large from entering into the motor fan. Of course this will save the motor. This is the only reason to have a wet filter. Machines that has no wet filter but only a “general filter” have the problem of after picking up dust and debris, the incoming liquid will create a mud cake on the filter surface. This cake will impede the vacuum cleaner performance. It stands to reason, if the filter is filled with mud, than less air will able to go trough it. This is why we use two (2) filters, one dry and one wet filter.
The filter is made from a very durable polyester material which is a screen or mesh. It will last for years. If you want to keep it clean, just wash it.