How To Sanitize Your RV Fresh Water Tank

Your RV’s holding tanks need to be maintained properly for you to enjoy camping to its fullest. This is especially true for your source of fresh water in your RV. Your freshwater system not only needs to work right, but it needs to be clean too.

How Often Should You Sanitize Your RV Fresh Water Tank?

Each year, usually in the spring when you get your RV out of storage, you should sanitize the fresh water system. This is a routine maintenance task to guarantee you have safe water for drinking, showering, dishwashing, and doing laundry on the road.

While you can pay a professional to sanitize your RV fresh water tank, there’s really no need. It doesn’t require any special tools and you can do it with bleach or a more environmentally-friendly cleaning solution if you prefer. 

How To Sanitize RV Fresh Water Tank with Bleach

To sanitize your RV water tank, all you need is a measuring cup, a funnel, and some household bleach. From there, just follow these step by step instructions:

Step 1: Turn Off Your Water Heater and Water Pump

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Draining your freshwater system with the water heater on can damage the water heater tank. Turn off your water heater and let the water in the tank cool before you drain it. If your RV is equipped with a water heater bypass switch, use it to prevent the bleach solution from entering your hot water tank. 

This is also the time to make sure your water pump is turned off. Opening all the faucets in your kitchen and bathroom will allow air to naturally assist in the complete draining of water from your fresh water system (this is similar to removing the cap on a car’s oil inlet before draining the oil). 

Make sure your grey water holding tank is empty before continuing. Or if you’re in a good location to do so, you can set up your sewer connection to an outlet so that you can empty your holding tanks easily when the time comes.

Step 2: Drain The Fresh Water Tank

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To drain your freshwater system, you’ll need to locate the low-point valves underneath your coach. Most RVs are equipped with two of these valves. One will be attached to a red water line (hot water) and the other will be at the end of a blue water line (cold water). 

If your tank is already empty because you drained it when winterizing your RV skip to Step 3.

Most RVs have a low-point valve directly underneath your freshwater tank. Some have multiple valves for the cold water system depending on the locations of the low points in your coach’s plumbing. 

Consult your owner’s manual if you’re having trouble locating these valves on your RV. 

Then you’ll simply need to open these valves to drain the water supply from your freshwater tank, plumbing lines, and hot water tank. Just be sure you’re in an area where water will percolate into the soil or run downhill in a safe manner. For example, you don’t want to do this in an RV park if the slope is going to create a pool of water in your neighbor’s site.

Pro tip: Now is a great time to check the hose clamp on the filler tube for your freshwater tank. This clamp must be tight before your freshwater tank is filled, and it can sometimes be left loose on new RVs. You’ll find this clamp on the side of your freshwater tank closest to the fill inlet. On some trailers, the water tank will be in an underneath storage compartment or it may be located under the bed of smaller trailers. 

Step 3: Calculate the Amount of Bleach You’ll Need

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While your system is draining, calculate how much bleach you’ll need to sanitize your system. You’ll need about a 1/4 cup of bleach for every 16 gallons of water your fresh water tank holds. Another helpful ratio for your calculator is to use one ounce of bleach for every eight gallons of freshwater. 

Measure the appropriate amount of bleach for your RV based on one of those ratios. For example, if you have a 20-gallon freshwater tank, you’d need roughly 2.5 ounces of bleach to sanitize your system.

Once there’s no longer any water draining from your low-point valves, cap them again. 

Step 4: Add Bleach Mixture to Your Fresh Water Tank

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Next, don’t add the bleach straight to your freshwater tank. Dilute it in at least a gallon of water and use your funnel to pour your bleach mixture into the fresh water inlet on the side of your RV.

Pro tip: If your RV has an overfill vent on the freshwater inlet, you may not be able to pour in your bleach solution using a funnel. In this case, simply pour the solution into your hose and hook it up to a water source to get the bleach into your tank.

Step 5: Fill the Tank with Potable Water and Pump It Through The System

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The next step is to fill your tank with clean water. Connect your water hose to a freshwater connection and fill your tank completely so that it mixes your bleach dilution through the entire tank. 

You may also consider using an RV water filter when filling your tank to use the cleanest water possible when sanitizing your tank.

Once your tank is full, replace the cap on your freshwater inlet. Next, you’ll need to circulate the bleach solution throughout the plumbing lines. 

Go inside your RV and turn on your water pump. Then open all the faucets and showerheads and allow the bleach water to run through every part of your freshwater system for 2-3 minutes. 

Once the water has circulated through for several minutes, you can close the faucets and shut off your water pump again.

Step 6: Let The Water Sit For 12 Hours

Proper tank sanitization doesn’t happen immediately. Let your mixture of clean water and bleach sit in your tank and plumbing lines for about 12 hours before draining it again. If you start this process in the afternoon, just let it sit overnight and then come back in the morning. 

Step 7: Drain the Tank

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After at least 12 hours, it’s time to drain all the water out again. Your first option is to do this the same way you initially drained your tanks to prepare for sanitization. Open the low-point valve (or valves) and allow the water to drain completely. 

If you’re using bleach, it’s recommended to avoid draining your tank into the soil, as it can be harmful to plant life and overall soil health. An easy solution is to place a five-gallon bucket or a portable RV holding tank under your low-point valve to collect your bleach mixture and then dispose of it into an appropriate sewer inlet, such as those at RV dump stations. 

Your other options are to use a biodegradable cleaner or turn on your water pump, open all your faucets (plus the shower), and let the water move through the system and into your grey water tank, provided you’ve already hooked it up to a sewer connection. 

Bleach and rubber aren’t the best of friends, so you don’t want to let this solution sit in your grey holding tank. But running it through as you flush the system isn’t likely to cause damage and can also partially sanitize your grey tank at the same time. 

If you do run your bleach mixture through your plumbing system and into your grey water tank, it’s still best to open the low-point valve after you shut off your water pump. This allows your freshwater tank to drain completely and prevents a small amount of water and bleach from getting left behind. 

Step 8: Flush The System

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Your final step is to refill your tank with fresh water and circulate it through the system with your water pump. Open all the faucets and flush the system until you can no longer smell the bleach. At this point, you can leave the handle for your grey water tank open so the system remains open as you flush the remaining bleach solution. 

You may need to refill the tank and flush it several times until the smell of bleach is long gone. This ensures you have eliminated all of the sanitizing chemicals from the system and you’re ready to use the water in that tank again. 

PRO tip: If your RV is equipped with an onboard water filtration system, it’s a good idea to replace your filters after the sanitization process. You can learn more about how to get clean drinking water in your RV here, including details on water filters and water quality. 

After you’ve replaced those filters, you’re safe to disengage your water heater bypass switch (if applicable) and you should be ready for another full year of camping. If you’re not heading out for a trip immediately, it’s best to leave your tank empty until you actually need water for use inside your RV.

How To Sanitize RV Fresh Water Tank Without Bleach

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If you don’t want to use bleach, there is a more environmentally-friendly way to sanitize an RV freshwater tank. You will follow the same basic steps outlined above, but substitute a biodegradable cleaner like this freshwater system cleaner from Camco in step three.

Make sure any RV fresh water tank sanitizer you choose is approved by your RV’s manufacturer and you follow the instructions carefully to use the correct quantity for the size of your freshwater tank. 

Best RV Fresh Water Tank Sanitizer

If you’re looking for a complete freshwater tank sanitizing solution, we also recommend checking out this all-in-one kit from Thetford. It’s an easy two-part system to clean and sanitize your freshwater tank while removing harmful bacteria so you can enjoy safe water on all your upcoming RV adventures.

Fresh water isn’t something to take for granted when RVing. Luckily, this sanitization process is easy to do and you only need to do it once a year to get back to enjoying the benefits of living in an RV.

What’s been your experience sanitizing your RV’s fresh water system? Leave a comment below!

If you’re still learning the ins and outs of RV maintenance, check out our downloadable RV ownership and maintenance booklet!