Sanitizing an RV fresh water tank without bleach
Most instructions still say household bleach, and the alternatives usually offered beside it — vinegar, baking soda, hydrogen peroxide — come with a caveat from the people recommending them: they do not work as well unless you heat them first. Chlorine dioxide is what the registered label covers for this job, at a stated strength and a stated contact time.
How much, by tank size
The one-hour procedure, which is the usual choice: less product, a longer wait.
| Tank | Purogene | Citric acid | Stand for |
|---|---|---|---|
| 20 gal | 6.4 fl oz | 0.8 oz | one hour |
| 40 gal | 12.8 fl oz | 1.6 oz | one hour |
| 55 gal | 17.6 fl oz | 2.2 oz | one hour |
The procedure
- 1Drain the tank and remove any sediment.
- 2Fill the tank with the sanitizing solution.
- 3Draw a little of it from every outlet, so the taps and lines fill too, then top the tank back up.
- 4Leave it to stand for the time the procedure calls for.
- 5Drain, and flush the system through with potable water.
- 6Refill with potable water, or with water treated at 1 to 5 ppm.
Step three is the one people skip. The tank is not the only thing holding water — the lines and the taps do too, and drawing the solution through every outlet is what gets it there.
Mixing it
Combine the Purogene and the citric acid in a plastic container and leave it five minutes, then dilute with two gallons of potable water before it goes anywhere near the tank. Pour that in, fill the tank, and start the clock.
Restated from the approved label for EPA Reg. No. 9804-5 — read it here. It opens by saying that it is a violation of federal law to use the product in a manner inconsistent with its labelling, which is why this page restates rather than improves.
After it is clean
Water that sits in a sealed tank keeps better if it is treated as it goes in: one fluid ounce per 30 gallons. A 16 oz bottle covers 480 gallons of that, which is a season or two of refills. See the sizes →