Just take the top of that big jug off, and start cleaning. There might be a 'sock' .... a slug of tee shirt material in there with a plugged up screen can... I still haven't dealt with the cotton thing, but the screen was very dirty. I doubt there is another filter, except maybe a screen in the 4 way valve body??? There's a can of worms... So far... you haven't had any bad luck at all!