Gray water tank won't empty

Hi all,

When we dumped our tanks last weekend, we got little if anything from the gray water tank. I postulated that it was because our TM was very lopsided at the dump station so we decided to leave things be and head on home. The co-owner of the trailer attempted to dump the gray water tank yesterday (trailer is on level ground) and while she got some drainage, it still wasn't the volume she expected. The system panel light indicates the gray water tank is still 1/3 full.

I have suggested that she try putting the curb side wheel on blacks to tilt the trailer towards the dump valve and/or taking the trailer for a spin in the hopes that water sloshing around will loosen/break-up any clog.

Anyone have any other ideas on what could be keeping the tank from draining completely and how we might fix it?

Thanks!