dw isn't draining completely. Can't find a piston/nut assembly part on the parts diagram for the GSD2200G02cc model. Extensions have been put on the S trap on under sink drain which elevates the drain hose from floor area up to very underside of sink. Is this too high to allow the dw to pump out all the water? Have cleaned the filter and sump cover but still not draining. Is there another part other than piston/nut could need replaced or have I overlooked that part on diagram?