Our tanks were cleaned yesterday and lessons were learned. I'll post tips from the tank guru. (Black Pyramid or TEE-Pee had formed like concrete in the black tank) I have not proven these tips but they come from people who clean these thing for a living. 1. KEEP ALL TANKS CLOSED. Let water out as needed for showers but keep all tanks closed - even when hooked up to campground sewer. Dump gray tanks when black tank is dumped. Not an absolute but liquid soap is better than bar ...