Trip Tool · Calculator
RV Waste Tank Estimator
Predict how many days until your gray and black tanks fill, and which one will run out first. Plan dump stops and stretch your off-grid time with water-saving tips.
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Quick answers
Frequently asked questions
How often do I need to dump my RV tanks?
A family of four with a 40-gallon gray tank and 30-gallon black tank typically needs to dump every 2 to 3 days. Conservative water users can stretch to 4 days, while heavy shower users may need a dump every day. The calculator above predicts exactly when each tank will fill.
Which fills up first, gray or black tank?
The gray tank (shower and sink water) almost always fills first because showers and dishes use far more water than the toilet. Most RVers need to dump the gray tank twice for every one black tank dump. Plan dump stops around the gray tank, not the black.
How many gallons per shower in an RV?
A typical RV shower uses 2 to 3 gallons per minute. A 5-minute shower uses 10 to 15 gallons. Navy showers (wet, soap, rinse) cut this to 2 to 4 gallons per shower and dramatically extend your gray tank runway.
Can I dump my RV tanks at home?
Only if you have a proper residential sewer cleanout and a legal dump hose connection. Dumping into a storm drain, yard, or septic system is illegal in most areas and can carry steep fines. Use a campground dump station, truck stop, or municipal RV dump instead.
How do I find an RV dump station near me?
Use the Sanidumps website or app, Campendium, or the RV Dump Stations app. Many truck stops (Flying J, Pilot) and some state parks offer dump stations for a small fee ($5 to $15). Many RV parks let non-guests dump for $10 to $20.