Glass of water


Freshwater tanks are pure evil.

That vile, insidious freshwater tank. It lurks silently in darkness. Hidden in a crevice, deep in the bowels of your RV. It is a silent killer, which strikes without warning or mercy.

Your freshwater tanks can be a good servant, but it is a cruel master. It demands that you serve it, that you lavish it with love and care, and selflessly cater to its needs. If you fail, it might just kill you.


Tap water is not sterile. “Safe” water simply has a “safe” amount of bacteria in it. If conditions are right, bacteria can multiply to unsafe levels in your tank and pipes.

Germs love to live and grow in water when it has not been treated with disinfectant, like chlorine. Bacteria loves water that is stagnant (not flowing), and sits for long periods of time (like a week or more). Stagnating water in your “freshwater” tank, is scientifically labeled Trapped water stagnation.


Waterborne bacteria can cause vomiting, diarrhea, and a host of stomach illnesses. Showering in unsafe water can cause illnesses of the skin, eyes, ears, lungs, and brain. It is estimated that one in fifty Americans suffer from a waterborne related illness. If you’ve ever gotten sick after an RV trip, your freshwater tank should be a likely suspect.

People at greater risk of waterborne illnesses include: infants, smokers and previous smokers, people with underlying diseases such as diabetes, people with health problems, people over the age 50.


FAT TOM is an acronym for the elements needed for bacteria to multiply and thrive. These elements, present in many or most RVs, are as follows:

Food– As stated, tap water is not sterile. Bacteria feeds on molecules of organic matter, as well as on many minerals.

Acidity– While the PH of pure water is neutral, the PH of tap water can be slightly alkaline to slightly acidic, due to minerals present. Bacteria can grow in either condition, but thrives in a slightly acidic environment.

Temperature– The danger zone is 40° -140°F, but temperatures between 70° -125°F provide the most hospitable environment for bacteria to thrive.

Time– While some foods can become unsafe after only an hour or so in the Danger Zone, water takes closer to a week to become unsafe, if conditions are right. Just neglect your freshwater tank long enough, and the grim reaper may come-a-calling.

Oxygen– Adding fresh water won’t make stagnant water safer. Along with adding a new food source, you will be adding air into the water.

Moisture– It’s water. Duh.


Always drain your water system if not in use. Never leave water sitting in your tank for a week or more. Before using, flush the pipes and faucets by running water through them for a couple of minutes. Always use a designated hose to fill your freshwater tank. Keep that hose clean, and add a filter. While a water filter will not filter bacteria, it removes impurities that bacteria feed on. Routinely flush the filter, as it can actually create a more ideal environment for bacteria to grow. Routinely sanitize your water system.


Cleaning and sanitizing your freshwater system should be a routine maintenance procedure. RVers debate on how often to do this, with views ranging from after every trip, to once a year. If you routinely neglect your water tank, and let water stagnate in it, you should sanitize more often.

To sanitize your freshwater tank, fill the tank with fresh 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.

While bacteria thrives in a slightly acidic environment, it can 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.

Seriously, who knows what evil lurks within the bowels of your freshwater tank, waiting to ambush you?

Freshwater tanks are pure evil.

Be safe.

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