Your RV Water System Isn't Like The One At Home
The fresh water tank in your RV holds the water you drink, cook with, and bathe in. Unlike a home water system fed by a continuously treated municipal supply, your RV tank is filled from a different source at almost every stop — city water hookups, well systems, campground supplies, and water stations of varying quality. Bacteria, algae, and other contaminants can establish themselves in standing water, in tank walls, and in water lines, especially during storage or periods of infrequent use.
NFPA 1192, the standard that governs RV construction and systems, requires potable water tanks to be sanitized before use. In practice that means sanitizing at the start of every season, after any period of extended storage, any time the water has an off taste or odor, and any time the system has been opened, repaired, or exposed to potential contamination.
What bleach to use: Standard 5.25% unscented household bleach is the correct product for RV water system sanitization. The ¼ cup per 15 gallons formula this calculator uses is calibrated for that concentration. Scented bleach and splash-less bleach both contain additives that are not safe for drinking water lines. Concentrated bleach (8.25% or higher) requires a different dilution ratio — do not use this calculator with concentrated bleach without adjusting your quantity.
How Much Bleach Do You Need?
Enter your fresh water tank size in gallons and get the exact amount of unscented household bleach to sanitize your system. Results update as you type.
- Bypass the water heater first. Bleach damages aluminum anode rods and causes rotten egg odor when heated through an active water heater.
- Unscented bleach only — standard 5.25% sodium hypochlorite. Scented or splash-less bleach contains additives that are not safe for drinking water lines.
- No hot water when mixing or flushing. Use cold fresh water only.
- Let it sit 4–24 hours after running to all faucets, then drain and flush completely until no bleach smell remains.
- Only after flushed: remove water heater bypass, refill, then turn heater on.
Enter Your Tank Size
How To Sanitize Your RV Fresh Water System
Use the calculator above to determine your bleach quantity, then follow these steps in order. Do not skip the water heater bypass step or attempt to rush the soak time.
- Bypass the water heater. Locate the water heater bypass valves — typically in the same compartment as the water heater or in a utility area inside the RV. Set them to the bypass position before proceeding. This keeps bleach solution out of the water heater tank.
- Drain the fresh water tank completely. Open the fresh water drain valve and all low-point drains. Let the tank empty fully before adding the bleach solution.
- Mix bleach with water in a separate container. Add the measured bleach to at least one gallon of clean water in a bucket or jug. Never pour undiluted bleach directly into the tank.
- Add the diluted bleach solution to the fresh water tank through the tank fill inlet. Then fill the tank completely with clean potable water.
- Run the solution through the entire system. Turn on the water pump. Open each faucet one at a time — both hot and cold sides — and let water run until you detect a clear bleach odor at that outlet. Do this at every sink, shower, and outdoor shower. Close the faucet and move to the next.
- Let the system soak for at least 4 hours. Close all faucets and let the bleach solution remain in the tank and lines. Overnight (8–12 hours) is ideal for a thorough sanitization or a system that has been in storage.
- Drain the entire system. Open the fresh water drain and low-point drains. Let it empty completely.
- Refill and flush. Refill the tank with clean potable water. Run all faucets until no bleach odor is detectable. If a bleach smell persists, drain and repeat the flush. It may take two or three flushes to fully clear the system.
- Return the water heater to normal operation. Remove the bypass, refill the water heater tank, and turn the heater on according to its normal lighting or startup procedure.
If your RV has a bypass for the tankless water heater, use it — that is the preferred method. If the unit cannot be easily bypassed: turn the heater off, and check the manufacturer's manual for its specific sanitizing procedure. Some manufacturers permit a very dilute chlorine solution to pass through the unit. Others specifically instruct owners not to run bleach through the heater at all and instead to sanitize the plumbing while isolating the heater.
Certain tankless models — including some Truma and Girard units — have sanitizing procedures that differ from standard RV plumbing procedures. The safest procedure is always the one in the manufacturer's manual. When in doubt, contact the manufacturer directly before running any bleach solution through a tankless unit.
Sanitization Has Limits
Regular sanitization keeps a healthy water system clean. It does not fix mechanical problems. Stop and get professional help in any of these situations.
- Water remains discolored, has an unusual odor, or contains visible sediment or particles after multiple sanitization and flush cycles. This can indicate tank damage, contamination of the fill line, or a more serious system issue.
- The water pump won't prime, pulses continuously without building steady pressure, or has lost significant flow. These are signs of pump wear, a failed check valve, or an air leak — sanitization will not address them.
- You find any leak at tank fittings, line connections, the pump, or the water heater. Any water line or fitting repair requires re-sanitization of the affected section afterward.
- The water heater bypass valves are difficult to operate, leaking, or the bypass configuration is unclear. Forcing stiff valves can damage fittings and create leaks inside the RV.
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