how to sanitize RV water tank

How To Sanitize RV Water Tank

One of the most important items for an RV’s regular maintenance is the fresh water tank. Leaving the water sitting too long means bacteria, mold and mildew can grow, contaminating the water, giving it a bad taste and resulting in health problems.

Each year, when you get your RV out of storage, you should flush the freshwater system. It is a time consuming process, but this article will teach you the different methods on how to sanitize RV water tank and walk you through the steps.

How Often and When To Sanitize Your Fresh Water Tank

The biggest reason for regularly sanitizing RV water systems is ensuring you have clean, healthy water to consume. What happens in the tank is as you use up the water in the tank, the water level lowers. The space above the water quickly builds up moisture, making it a perfect breeding ground for all sorts of contaminants including mold, mildew, and bacteria, causing adverse health concerns. 

This is also why water that sits in the tank for a while becomes stale and has an unpleasant odor and taste. Another reason for cleaning RV fresh water tank is mineral build-up, which can clog your water lines. 

The only way to prevent this is to regularly flush your entire water system with a potent sanitizer to get rid of unwanted contaminants and mineral buildup. You should sanitize your RV fresh water tank when:

  • You should also always clean the tank out when you buy a new RV, whether it’s new or used.
  • At least every six months is the recommended amount of time for any full-time RVers. Many campers who travel with small children even recommend sanitizing RV freshwater tank every three to four months to ensure they are consuming clean water.
  • Or whenever the water starts to have a stale odor.
  • When you take it out of storage, usually after the long winter and at the beginning of spring. 
  • Or any time the RV has been sitting around two weeks or more and the RV water system has not been used, the old leftover water in the tank will get stale. You must clean it out with a sanitizing solution to get rid of the impurities that will ruin the taste and smell of your drinking water.
  • If you fill the tank at a campground where the water isn’t healthy to drink, your water line will now become contaminated. 
  • If you find algae or slime in your water tank.
  • If you have been informed that there is a boil water advisory from the authority.

Even in the case that you do not drink water out of your freshwater tank, if one or more of the above conditions are true, it’s still highly recommended that you thoroughly sanitize your entire fresh water system. You won’t want to take a shower in bacteria-filled and foul-smelling water. 

And if you’re counting on water filters to purify water for drinking and cooking, note that  filter is not a purifier and will not kill bacteria, although they will remove contaminants and improve taste and odor to some extent.

How To Sanitize RV Fresh Water Tank with Bleach: What You Need

The three major types of harmful bacteria that you need to get rid of from your drinking water are Listeria, E. Coli and Salmonella. Chlorine bleach, hydrogen peroxide and white vinegar can kill all three types of bacteria, while another popular household cleaning agent, baking soda, has proven to be ineffective.

But, and this is a big but: At room temperature, hydrogen peroxide or white vinegar are not effective. In order to be effective, they must be heated to at least 130°F or about 55°C to kill all three of the bacterias. 

So we’ll start with how to sanitize RV fresh water tank using bleach first. While many may cringe at the idea, it’s a fact that most municipally provided sources of water are treated with chlorine or bleach before they are supplied for human consumption.

How to sanitize RV fresh water tank with bleach? Rest assured that it’s straightforward and intuitive; you just need a little bit of planning, since it takes half a day from start to finish. You’ll only need the cheap and easy to find household items below:

  • Chlorine bleach: Do not use a general cleaning solution that contains bleach. Use bleach only (note that bleach and chlorine are the same chemical. They are a dilute solution of sodium hypochlorite)
  • A plastic 1-cup measuring cup to measure the right amount of bleach to use.
  • A plastic pitcher of at least one gallon in volume for diluting the bleach before pouring it into your freshwater tank. If you also want to try out how to sanitize RV water tank using vinegar, you should get a 15-gallon or 20-gallon container for diluting solutions.  
  • One clean funnel that has been kept away.
  • White hose with which to refill the freshwater tank with clean water.

How To Sanitize RV Fresh Water Tank with Bleach/Chlorine: Step by Step Guide

The process of sanitizing RV freshwater tank is fairly easy. In broad strokes, it includes draining your fresh water system, then filling the fresh water tank with the bleach solution, then running the solution through the whole water line by opening each faucet and shower, let the solution sit for long enough within the water line, and lastly, drain and refill the tank until no traces of bleach can be detected.

How this all works is quite intuitive and easy to understand and follow. It just takes about 5 hours up to 12 hours from the first step to the last step to properly sanitize a contaminated water system. In some cases, you might need to repeat the last step to make sure the whole water system is rinsed clean and after refilling the tank, the water coming out will not smell like bleach.

12 hours might make you shy away from the job, but this is because the major portion of the time is for letting the solution sit in the tank long enough to actually kill any bacteria and buildup. For best results, you need a total of 12 hours. 

The step-by-step instructions below are for generic RVs and trailers. As with any other maintenance task, make sure you consult your owners manual for specific steps related to your make & model.

Safety note: Put on old clothes and shoes, as even tiny splashes of bleach will spot your clothes.

Note About The Water Heater 

Many campers choose to sanitize the cold water lines along with the hot water system as well, while many professionals and full-time RVers advise that you should not drain the freshwater system with the water heater on. The reason is chlorine or bleach will damage the water heater, and the hot water system should be bacteria-free due to the high temperatures. 

However, there’s no harm in cleaning out the hot water system together with the cold-water lines, given that you’re sanitizing with a safer solution other than bleach. Actually you can even take advantage of the water heater to effectively heat up a homemade sanitizing solution with vinegar and flush the system with this hot vinegar. You will learn the steps for this method in the next section.  

Step 1: Drain The Freshwater Tank

If you choose to sanitize the cold water line only, you need to turn the water heater off and let it cool before you drain the system. Remember to also turn off the ice maker, if any. You can leave the water pump on. Opening the drain valve to drain the fresh water tank, then close it again.

Step 2: Dilute The Bleach and Pour The Solution Into the Freshwater Tank

Refer to your owner’s manual to find out how many gallons your fresh water tank holds. This is crucial to calculate the right amount of bleach to use. Remember that over concentration of chlorine is unwanted due to health concerns and the chemical odor. 

The safe ratio is one ounce or ⅛ cup of bleach for every eight gallons of water in your freshwater tank. For instance, if your RV has a 36-gallon tank, you will need 4.5 ounces or ½ cup of bleach. Although this might sound negligible, bleach is very strong, and we’re talking about drinking-water lines here. This amount is enough to sanitize the water tanks and lines. 

An important note is never pour the undiluted bleach straight into your freshwater tank, as it will damage the tank and seals. Dilute the amount of bleach you just calculated with at least a gallon of water. Then using a clean funnel, pour this diluted solution into the freshwater tank.

Step 3: Fill the Freshwater Tank and Run The Bleach Solution Through Every Fixtures

After pouring the diluted bleach solution into the freshwater tank, now hook up a white hose to a source of clean water and fill the tank up all the way until you see overflow beneath the tank. If you underfill, as explained above, the bleach solution might not be diluted to the recommended level and might harm your lines. Plus, you need enough solution to sanitize every nook and cranny of your water system.

Turn the water pump back on as now you’re gonna run the solution in the tank to every fixture on your RV. Remember to bypass any water filter you have so bleach doesn’t reach it.

To make sure the bleach solution reaches every part of your water system, open the cold side of each faucet and shower, including any exterior faucets or showers, until you smell bleach at each. Open each fixture one at a time, then turn it off and move to the next one. 

Note that here, you’re opening the cold faucets only because you’re sanitizing just the cold-water lines. If you’re also rinsing the hot water system, turn the heater back on before you turn on the water pump, and at this step, you’ll be opening both the hot and cold sides of all faucets and showers.

Lastly, open the gray water tank drain valve to capture the bleach solution. 

Step 4: Let The Diluted Bleach Sit In The System Ideally Overnight

The bleach is well diluted, so running it through your water system for 15 minutes or so will not cleanse any contaminants. The solution needs to sit in the tanks and lines to properly kill all harmful bacteria and rinse away mineral- and other buildups. 

Allow the bleach solution to sit in the fresh water tank and lines for at least 4 hours, if you have determined that your system is not so horribly contaminated, but for best results, the general recommendation is about 12 hours (basically overnight). You need quite a few hours to do the job anyway, so make sure you get it done well. The most convenient schedule is to fill late in the day and drain in the next morning, so that the solution will sit in the system overnight.

This is optional, but many full-time RVs recommend that you casually drive your RV a few miles to get the solution to splash around and reach every nook and cranny of the tank (remember that after filling the tank to full, you opened the fixtures to let the bleach solution run through, thus diminishing the water in the tank).

Step 5: Drain the Tank and Rinse the System To Get Rid of Bleach

After enough sitting time, you can drain all the water out again and then refill the freshwater tank with clean water. Turn on your water pump and open all faucets and showers to rinse off the bleach from your water lines. After you can no longer smell the bleach from any source, it’s safer to run the clean water through for a bit longer just to make sure.

You might not get all of the bleach out after just one flush. If you can still detect the smell of bleach, refill the tank again and flush until the bleach smell is gone, then refill. It’s actually better to repeat these steps for at least once even after the bleach smell is gone to make sure your drinking water is free from any chemicals.

The last thing to do is to turn the water heater and any water filter back on. Tighten the drain on your gray water tank, or dump it at a station.

How To Sanitize RV Fresh Water Tank with Vinegar: Step by Step Guide

Using bleach is the most common method. However, it’s better and safer to sanitize RV fresh water system without bleach of course. When you attempt to treat your own freshwater tanks with bleach, you risk over-concentration, which can have disastrous health complications, and potential plumbing problems.

A super effective yet safe approach that countless campers advocate for is using vinegar. White vinegar at most stores has an acidity of 5% on average, and this cheap solution makes a perfectly effective and safe cleaning and deodorizing agent.

Just note that to be most effective on a contaminated water line, the vinegar solution must be heated to at least 130°F or about 55°C. Still, cleaning RV hot water tank with vinegar is a great in-between or gentler “maintenance” type of system flush when your tanks are not in terrible condition and thus might not require bleach as a strong disinfectant.

If your priority is to be chemical-free and ecologically friendly, then using a hot vinegar solution is the best choice. Plus, using vinegar instead of synthetic chemicals is way safer for you and your passengers. Using vinegar takes a little extra work but if you have the thread adapter for the kitchen sink, the process is just the same and is pretty easy.

cleaning rv fresh water tank
Photo: EyesWideOpen / Getty Images

Why Vinegar Is Great and How To Get Hot Vinegar

So, how to disinfect RV water tank with hot vinegar of at least 130°F or about 55°C? While this might sound like a quest, there is actually a very fuss-free and convenient way to achieve this, and that is to use your RV’s hot water heater to heat the vinegar solution to the desired temperature. And the beauty of using hot vinegar as a sanitizing solution is that it actually kills two birds with one stone.

It turns out that in addition to sanitizing your freshwater system and killing harmful bacteria, hot white vinegar is also perfect for removing the mineral deposits that build up in your hot water tank and on its anode rod. The anode rod used in the heater is prone to corrosion, which produces hydrogen sulfide that smells like rotten egg.

If you’re not yet convinced, your coffee pot is a great proof of the wonders of warm vinegar. It is recommended by the manufacturers of most coffee makers that if you notice white mineral deposits in your coffee maker, try running white vinegar through the coffee maker to clean it. 

When vinegar is circulating in the machine, it is heated up, just like the water for your coffee, and it gets rid of mineral buildup like magic. It’s the same exact principle here with your RV freshwater system. 

What you’ll need:

  • White vinegar (Any type of white vinegar used for cooking. Most vinegars have an acidity of 5%. The mixing ratio further below is based on this average level of acidity.)
  • A container of at least 15 gallons in volume to mix the vinegar solution.
  • A clean funnel for pouring the solution into your freshwater tank.
  • A thread adapter to attach a garden hose to your RV kitchen faucet. You can purchase one from Amazon, Walmart Home Depot, or Lowes. 
  • A white hose to fill the tank from a clean water supply.

Step 1: Drain The System and Preparation

Turn off your water heater and set the temperature to over 130°F or about 55°C while it is off. Drain all the water from your water system and hot water tank.

Mix the white vinegar and water solution with a 1:1 ratio. Prepare at least 15 gallons of the diluted solution.

Step 2: Fill The Fresh Water Tank With Vinegar Solution

Fill your fresh water tank with at least 15 gallons of the diluted vinegar solution using a clean funnel. Open the cold side of your kitchen faucet and run your water pump until water comes out and you can smell vinegar. 

Now turn the water off and turn on the water heater. It will take at least 20 minutes for the water to reach 130°F or about 55°C and above.

Step 3: Fill The Fresh Water Holding Tank With Heated Vinegar 

While the vinegar solution is being heated up, attach a thread adapter to the kitchen faucet. Attach a garden hose to the thread adapter and run the hose to the fresh water fill up outside of your RV.

When the solution is all hot and ready, turn on your water pump. Now we’ll fill the fresh water holding tank with the hot white vinegar solution by opening the hot side of the kitchen faucet.

Step 4: Run the Hot Vinegar Solution Through The Whole System

Once your fresh water tank is filled with the hot vinegar solution, you need to circulate the hot solution through every hot and cold line of the system. Open both hot and cold sides of each faucet and shower, including exterior fixtures, one at a time, until you smell vinegar. Be careful, as temperatures over 130°F or about 55°C can cause scalding.

Remember to run both the hot and cold sides of each fixture and remember to run the cold side of the kitchen faucet last. You should be getting hot water out of both sides. 

Don’t forget to also run the solution through the drinking water dispenser in the fridge door, your ice maker or instant hot.

Step 5: Let The Solution Sit Overnight then Rinse Out The System

Once the hot vinegar solution is pumped through every hot and cold line to every faucet and shower, you can disconnect the garden hose and let the vinegar work it wonders overnight, that is for at least 12 hours ideally.

The next day, you’re gonna drain the tank and rinse out the vinegar solution, so the first thing to do is to turn off your hot water heater. Remove the anode rod, drain and rinse out the water heater thoroughly. There might be quite a bit of sediment when you rinse out the water heater. When the water coming out is clear from sediment, re-insert the anode rod and then set the hot water heating temperature back to your preferred range. 

Use the while hose to hook up to a clean water source and run it through both the hot and cold sides of all of your faucets and showers until the vinegar odor cannot be detected. Continue for a bit longer to make sure everything is thoroughly cleansed.

Follow Up A Vinegar Flush With Baking Soda

Another homemade solution that can be found in many kitchens is baking soda. It is safe and is known to be a natural deodorizing agent that also reduces dirt, grime and mineral buildups in the home. It can do these wonders to your RV water system as well, but unfortunately, if we’re talking about sanitizing and killing bacteria in the water lines, it is by far not as effective as bleach and hot vinegar. 

That said, many campers like to use hot vinegar to kill bacteria, and then neutralize the distinct odor with a follow-up cleansing using baking soda. Many claims that this might get rid of the smell faster without having to flush the system multiple times, thus wasting freshwater. 

By now, you should already have guessed the general process of how to sanitize RV water tank with baking soda. The process is essentially the same, but will not take your half a day like with bleach and vinegar:

Mix 4 liters of water with 1 cup of baking soda, then fill your freshwater tank with the well-mixed solution. This is optional, but many campers advise that you go for a drive for 15 minutes to let the solution mix around in the tank.

Unlike with a bleach or vinegar flush, you’re not trying to kill the bacteria here, so there’s no need to let the solution sit around for half a day. After filling the freshwater tank with the solution for about 15 minutes, open all the faucets and showers to let the solution run through the entire water line. 

Similar to the processes above, now refill your freshwater tank with clean water, then flush this clean water through your system to get rid of the solution by opening all faucets and showers until the water lines run clear (the solution with baking soda would be cloudy white).

How To Sanitize RV Fresh Water Tank without Bleach: Commercial RV Water Sanitizer

If you cringe upon hearing “bleach” in the matter of drinking water, but do not trust that vinegar is strong enough to kill bacteria, you have another option: commercial RV water sanitizer. There is a big, big market for such a product, as RV product manufacturers are well aware of the universal need for clean freshwater. You can find a staggering number of available options both online or in stores.

The safest bet is of course to read in-depth reviews of verified buyers. If we have to name a few, then Camco has long made a name for its superb RVs as well as functional RV accessories and products. And the manufacturer’s CamcoTastePURE Water System Cleaner and Deodorizer have become one of the more popular options among RVers these days. 

This product is bleach-free, and as sworn by users, can effectively sanitize the water system while also eliminating foul odors. You get the best of both worlds. Just keep in mind that CamcoTastePURE, as well as other commercial RV water sanitizer products, isn’t intended to be a water additive. 

Note: Stale Water Due To Problems With The Water Heater

As above, many campers suggest that you should not rinse your hot water system but only need to regularly flush your cold water line. However, it should be noted that flushing your water heater is not a problem if you don’t use chlorine. Furthermore, doing so can eliminate the common RV issue of water smelling like sulfur or like rotten eggs. 

This happens because the anode rod used in the heater starts to corrode and produces hydrogen sulfide which smells like rotten egg. To fix this headache, follow these steps below:

  • Replace the corroded rod.
  • Using aluminium rod can help avoid corrosion and thus the rotten-egg-smell problem.
  • You can try to make sure that the water is softer. Softer water has lower mineral content, thus the anode rod will be less prone to corrosion.

Last Updated on November 28, 2021

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