How Often Should You Dump Your RV Tanks?

Ask ten experienced RVers how often you should dump your tanks and you'll get ten slightly different answers. The honest answer is: it depends. It depends on your tank sizes, how many people are in your rig, how long you're stationary, and what kind of camping you're doing. But there are clear guidelines, concrete warning signs, and some important differences between your black tank and gray tank that every RVer should understand.

The Two Tanks and How They're Different

First, a quick primer for new RVers. Most RVs have two holding tanks:

• Black tank: Receives waste from the toilet only. This is the primary sanitation concern — it holds human waste and requires the most careful management.
• Gray tank: Receives water from sinks and the shower. Less problematic from a sanitation standpoint, but it can still create serious odor problems if left too long, especially in warm weather. Some larger RVs have two separate gray tanks — one for the kitchen sink and one for the bathroom.

These tanks are always emptied at a dump station or sewer hookup in a specific order: black tank first, gray tank second. The soapy gray water helps rinse the sewer hose after the black tank drains.

The Standard Rule: Two-Thirds Full

The most widely followed guideline is to dump your black tank when it reaches about two-thirds full — not when it's completely full. Here's why: a tank that is too full creates backpressure that can damage your dump valve, makes it nearly impossible to get an accurate tank sensor reading, and significantly increases the risk of a backup or overflow. Two-thirds is the practical comfort zone.

For most RVs with a 30 to 40 gallon black tank and two adults using the toilet normally, that translates to roughly three to five days before you need to dump. Full-timers, large families, or anyone with a smaller tank may need to dump more frequently.

How Often for the Gray Tank?

Gray tanks fill faster than black tanks for most people because every dish washed, every shower taken, and every hand washing adds to the volume. A 40-gallon gray tank with two active adults can fill in two to three days depending on water use habits. The good news is that a gray tank at or near full is much less of an emergency than a black tank — but you still shouldn't let it overflow, and the smell in warm climates can become significant after four or five days of use without dumping.

A good habit: dump your gray tank every time you dump your black tank, regardless of how full it is. This keeps both systems running cleanly and eliminates the need to track two separate schedules.

Signs Your Tanks Need Dumping

Your tank level monitors are a starting point, but they're notoriously unreliable in older RVs or rigs with dirty sensors. Trust these more reliable signs instead:

• Slow toilet flush: If the toilet flushes sluggishly or the bowl refills slowly, your black tank is getting full.
• Gurgling drains: Gurgling sounds from sinks or the shower when you run water suggests the gray tank is approaching capacity.
• Odors inside the RV: A persistent sewage smell inside the rig — even with all vents open — is a strong signal that one or both tanks needs attention.
• Sensor reading at 2/3 or higher: If your sensors are reliable, treat a 2/3 reading as your action threshold, not a warning to plan ahead.
• Days of use: When in doubt, count days. Three to four days of normal use for a couple is usually enough to warrant a dump regardless of what the sensors say.

Full Hookups vs. Off-Grid Camping

If you're at a campground with full hookups, you can leave your sewer hose connected to the site's sewer inlet — but with one important caveat: never leave the black tank valve open. Always keep it closed and only open it to dump when the tank reaches two-thirds full. Leaving the black tank valve open causes liquids to drain continuously while solids build up in the tank, creating the pyramid plug problem that's very difficult to clear.

The gray tank valve is less critical — many full-hookup campers leave it open continuously — but even gray water can leave mineral deposits and soap scum residue that clog your drain line over time. Dumping it periodically rather than letting it run constantly is a good practice.

Off-grid (boondocking) camping is where tank management really matters. Without sewer access, every gallon counts. Use a composting toilet if your rig supports it, conserve water aggressively, and plan your dump station stops as part of your route using our dump station finder before you head out to remote areas.

Building a Schedule That Works for You

The easiest approach is to make dumping a regular part of your weekly routine. Most RVers who travel consistently find that a dump every three to four days keeps both tanks comfortable regardless of the exact fill level. If you're stationary for a longer stretch, set a calendar reminder. Don't wait until the sensors scream at you — by that point you're already managing a problem rather than preventing one.

Planning your route around dump station locations is equally important. Browse dump stations by state at rvdumpstations.cc/states or search near your planned destinations to make sure you always have a viable option within a reasonable distance of wherever you're headed next.