A smelly black tank can ruin a trip. After 18+ years of RVing and 6+ years full-time on the road, the GEO Method is how we keep ours clean and fresh. It uses two things from any grocery store: Calgon water softener and laundry detergent.

What Is the GEO Method?

The GEO Method is a cheap, simple way to clean your RV black tank. Calgon water softener coats the inside of the tank so waste is less likely to stick to the sides. Laundry detergent cleans and deodorizes. Your drive does the scrubbing, because the mix sloshes around the tank while you’re on the road.

How to Clean Your RV Black Tank, Step by Step

1. Fill the toilet bowl with water.
2. Add 1 capful of Calgon water softener.
3. Add 1 capful of laundry detergent.
4. Flush, so everything drains into the black tank.
5. Drive to your next destination, then dump and flush the tank with plenty of water.

Tips for the Best Results

• Calgon is the key ingredient. The detergent matters less, so the cheapest brand works fine.
• Pick a strong-scented detergent. It helps cover odors.
• Rinse well. After dumping, flush the tank thoroughly to clear out leftover detergent and waste.

What to Avoid

• Harsh household cleaners like bleach. They can dry out and damage the rubber seals in your toilet and tank valves.
• Thick, regular toilet paper. It breaks down slowly and can cause clogs. Use RV or septic-safe toilet paper.
• Leaving the valve open while camping. Liquids drain away and solids get left behind.

How to Prevent Black Tank Odors and Clogs

• Dump and flush your tanks regularly.
• Use more water when you flush. Water is your friend for keeping smells down.
• Keep your black tank valve closed while camping. Never leave it open.

RV Black Tank Cleaning FAQ

How often should I use the GEO Method?

As often as you need to keep your tank clean and smelling fresh.

Does it matter which laundry detergent I use?

Not much. Calgon does most of the work, so any inexpensive detergent works.

Why keep the black tank valve closed?

With the valve open, liquids drain out but solids stay behind, pile up and cause clogs and odors. Keeping it closed until you dump lets everything flush out together.

Will the GEO Method fix my tank sensors?

It can help keep them reading correctly, but it won’t fix a sensor that’s already faulty.