Venta Airwasher Venta LW14

When you add water, you should notice bubbles (just a few) on top of the water.  When the water no longer has bubbles, the additive is shot, and you should wash out the tank.  We have dirty air, and it takes about 2 weeks for us.  I spray it with Murphy's Soap to soak a few minutes and wipe it out with a sponge.  Rinse.   Spray the wheel similarly (all over) and spray with a kitchen hose, as hot as possible.  You may have to repeat.  I clean my wheel between tank cleaning, so it doesn't build up.  You should use the additive, because the water has to be slippery to work with the wheel.  Maybe you can find a different "wetting solution,"  that would be cheaper;  Venta gets an arm and a leg for it.  Good Luck.  I like the performance of mine, but it is temperamental.