Black tank first. Gray tank second. Every time. No exceptions. The only rule that matters.
Dumping your tanks wrong costs money — in clogs, odor, and replacement sensors that read full when they're empty. This procedure covers the correct sequence (black before gray, always), the flush routine, and the treatment steps that keep your sensors reading accurately long-term. It takes about 20 minutes done right.
The only rule that matters
Always dump black tank before gray tank. Gray water acts as a final rinse through your sewer hose. Reverse the order and your hose stays dirty.
Tank Monitor Reality Check
Most built-in monitors read wrong after a few uses — sensors get coated and read "full" when they're not. Use the monitor as a rough guide. When in doubt, dump if you've been there 2–3 days.
Slope Matters
Hose must run downhill from trailer to dump inlet with no sags. Sags trap solids and cause backup, odors, and clogs.
The Clear Elbow Is Worth $8
You can't see through an opaque sewer hose. The clear 45° elbow shows you exactly when the black tank is empty and when flush water runs clean. Always in the kit.
Why Gray Goes Second
Gray water from your sinks and shower is relatively clean compared to black tank waste. Running it last sends a final rinse through the entire sewer hose before you disconnect.
Always Leave Treatment in the Tank
Empty tanks = odors. Enzymatic treatment needs water to activate and coat the tank walls. Don't leave the black tank completely dry — always add treatment + a gallon of water.
Black tank before gray. The gray water flushes the sewer hose after the black dump. If you dump gray first, you're using clean water to flush the hose before the dirty water goes through.
Keep your black tank valve closed between dump days. People who crack it to 'let things drain' end up with solids dried to the bottom of the tank — which is what causes persistent bad sensor readings.
A clear 45-degree elbow connector at the dump station tells you when your black tank is actually running clear. Without it, you're guessing how long to run the flush.
All 12 checklists, works without cell signal, installs to your home screen in one tap.