HOW TO FILL AND/OR SANITIZE YOUR RV FRESHWATER TANK
RVs have two ways to get water. You can connect a hose to the city water connection, which will supply water pressure to your RV. Or, you can fill the freshwater holding tank, and get pressure from the 12v water pump which senses the pressure demands to turn on and off automatically.
While many newer RVs have a switch over valve for filling the freshwater tank from a city water hookup, most RV freshwater tanks have to be filled by putting water directly into the freshwater tank. Regardless of how your RV freshwater system works, you have to make sure to fill the freshwater tank properly to avoid bursting it or damaging the plumbing.
To gravity fill the onboard storage tank, if your RV is not equipped with a switch over valve, run water directly into the water storage tank inlet (not the city water supply inlet). Use a potable water hose, rather than a regular garden hose (these are usually white or blue). It is also recommended that you use a water filter attached to your hose.
The main problem with filling your RV freshwater tank, is you have to do it slowly to allow enough air to escape that it won’t burst or damage your tank. Trying to fill the tank too fast, or not allowing air to escape, could destroy your tank, or its fittings and connectors. Some RVers cut off the end of the hose to remove the metal connector and allow air to escape more easily. But, if filling too fast, air could still be trapped inside, and destroy your freshwater tank.
My personal solution was to attach a length of 3/8 inch water supply tubing to a ¾ inch hose fitting, which allows the tubing to be inserted fully into the tank, allowing air to escape easily, with no chance of air being trapped. This not only prevents air from being trapped in the tank and greatly reduces the risk of damaging my freshwater tank, but now it only takes a few minutes to fill the tank. DISCLAIMER: Individual results may vary.
In addition to using a designated hose and a filter, you need to occasionally sanitize your freshwater tank. RVers debate on how often to do this; views range from after every trip, to once a year. To sanitize your freshwater tank, fill the tank with water, add ¼ cup of bleach (mixed into a gallon of water) for every 15 gallons of water in your freshwater tank. Turn on each faucet (hot and cold) until you smell bleach. Then, let the system set for several hours, or overnight. Lastly, drain the freshwater tank, refill with water, and run freshwater through each faucet to rinse out the bleach.
Bacteria thrives in a slightly acidic environment, but can also build tolerance to the bleach. Therefore, it may be wise to give the freshwater system a shock treatment, by sanitizing with vinegar, rather than bleach, at least once a year. Some RVers begin the season by doing the vinegar sanitation, following the bleach sanitation and rinse. Fill, sanitize with bleach, drain and flush, refill, sanitize with vinegar, drain, and refill.