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How often should you dump RV tanks?
Quick answer: Dump by tank level, not by the calendar. Empty the black tank when it is about two-thirds to three-quarters full so there is enough liquid to flush solids out, and empty the gray tank when it is close to full. Always dump black first, then gray.
How often that happens depends on your tank sizes, how many people are aboard, and how much water you use. A couple who takes short showers and uses campground restrooms might go a week or more, while a family using the RV's own shower every day may need to dump gray water every couple of days.
Black tank: wait until it is mostly full
The black tank holds toilet waste. It empties best when it is at least two-thirds full, because the weight of the liquid pushes solids and paper out through the valve. Dumping a nearly empty black tank leaves solids behind, and they can build up into a clog.
- Use plenty of water every time you flush, so solids stay wet.
- Use RV or septic-safe toilet paper that breaks down quickly.
- If you have a black tank flush, rinse the tank after dumping.
Gray tank: it usually fills first
The gray tank holds water from the sinks and shower. It often fills faster than the black tank. Dump it when it is close to full, but try to keep some gray water in reserve to dump after the black tank. That gray water rinses the sewer hose on its way out, as the step-by-step dumping guide explains.
At full hookups: keep the black valve closed
When you are connected to a campsite sewer, it is tempting to leave every valve open. Do not do that with the black tank. Liquid drains away and solids stay behind, which can leave a pile in the tank that is hard to clear. Keep the black valve closed and dump it when it is mostly full. Many RVers leave the gray valve open at full hookups, then close it a day or so before dumping black so there is gray water for the rinse.
Boondocking and dry camping
Without hookups, your tanks set how long you can stay. Conserve water, track how many days it takes your tanks to fill, and plan a dump stop before you are full. Browse dump stations by state and city or check each state's free list to find one on your way out.
Don't trust the sensors alone
RV tank level sensors are often wrong because waste and paper stick to the tank wall. Rinsing the tank helps, but many RVers rely on experience instead: note how many days a full tank takes, and dump on that schedule. The RV tank calculator turns your tank sizes and daily use into an estimate of days until dump.
Before storage or a long stop
Dump and rinse both tanks before parking the RV for weeks, so waste does not dry out and smell. In cold climates, the winter guide covers tank steps before winterizing. If your house is on city sewer, the dumping at home guide covers cleanout and macerator options.
What it costs to dump
Many dump stations charge a small fee and some are free. The dump station cost guide shows typical fees from listed charges, and the truck stop and 24-hour lists help on travel days.
Frequently asked questions
How often should you dump RV black water?
When the black tank is about two-thirds to three-quarters full. Waiting until it is that full gives enough liquid to carry solids out. For many RVers that works out to every few days, but it depends on tank size, how many people are aboard, and how much water you use, so go by the tank level rather than the calendar.
How often should you dump RV gray water?
Gray tanks often fill faster than black tanks because showers and dishes use a lot of water. Dump gray when it is close to full, and try to keep some gray water to dump after the black tank so it rinses the sewer hose.
Should I leave my black tank valve open at a full-hookup campsite?
No. With the black valve open, liquid drains away and solids stay behind and build up in the tank. Keep the black valve closed and dump it when it is two-thirds full or more. Many RVers leave the gray valve open at full hookups and close it a day or so before dumping black, so there is gray water to rinse the hose.
How long can you leave waste in an RV black tank?
There is no single safe number of days, but waste that sits for a long time can dry out, smell, and stick to the tank and sensors. Before storing the RV or leaving it parked for weeks, dump and rinse both tanks.
Why do my RV tank sensors always read full?
Tank level sensors are often thrown off by waste or paper stuck to the tank wall. Rinsing the tank with a built-in flush or a tank wand and using plenty of water when you flush can help. Many RVers learn their real fill rate by tracking how many days it takes to fill.
Where can I dump my tanks between campgrounds?
At a public dump station. This site lists 1,589 US dump stations across 49 states, including 175 tagged free, so you can usually find one on your route.
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