Black Tank Flush
A built-in hose connection on the RV exterior that sprays water inside the black water tank to clean residue after dumping.
Also called: black tank flush, black tank rinse, tank rinse, flush kit
A black tank flush is a built-in hose connection on the RV exterior that sprays water inside the black water tank to clean residue after dumping. Most modern RVs have one; older rigs don’t.
Why it matters
After a gravity dump at the dump station, some solids and waste residue stay on the inside walls of the black tank. Over time this creates:
- False “full” tank readings (residue covers the sensors)
- Persistent odor even after dumping
- Pyramid buildup (a literal mound of solidified waste under the toilet)
The flush sprays clean water inside the tank, dissolving and washing out residue.
How to use it
- After completing a normal dump, leave the gate valve open
- Connect a hose to the flush port (clearly labeled, distinct from the freshwater inlet)
- Run water for 3-5 minutes — water + residue flows out the dump hose
- Disconnect, close the gate valve
What it isn’t
The flush hose port is never connected to the freshwater system. The plumbing is intentionally separate to prevent any chance of cross-contamination.
If your rental doesn’t have one
Add a few gallons of fresh water and a packet of tank treatment after each dump. The water sloshes during driving and cleans the interior surfaces. Less effective than a built-in flush, but better than nothing.