How To Sanitize Your RV Fresh Water Tank 70255

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. Whether you’re traveling in a used motorhome such as a used towable or a brand new motorhome like a travel trailer, 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?

filling the water tank of a campervan in campground area

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

Photo by Tony Skerl via Shutterstock

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

PC Camping World

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!

Sanitize your RV's freshwater system in 5 simple steps

Tucker Ballister is a Technical Content Writer for Camping World and a lover of the open road. You can check out more of his adventures and outdoor advice at
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  1. FIRST Check to see the clamp on the filler tube on the inside of the camper is tight, I didn’t and filled the kitchen side of camper and underbelly with water. I’ve been told the clamp being loose on new models like mine are not uncommon

    1. What is the clamp on the filler tube? I’m not sure I understand this? Can you help me? We just got a new RV and wanna make sure to check that.

  2. My RV has a check valve or some type of valve that prevents pouring into the fresh water fill fitting. How do I get the bleach into the system?

    1. You pour the bleach into the water hose befor you hook up to camper. Then turn water on to fill and presto the bleach goes right in with the water.

      1. I’m going try a garden fertilizer injector from AMZ. I calculated that a 50G tank requires .78G of bleach (at 1/4c per G). The injector works at a 16:1 ratio, so the bleach should all be taken up with about 12.5 G of water, then let it continue to run as water-only to full. The injector is already performing dilution, so you should be able to drop the dip tube into straight bleach.
        One commenter said the injector didn’t draw well at his high hose pressure, and recommended only opening the spigot partially to find the best flow. I will probably just use one of my RV pressure regulators on the upstream side of the injector to address this.

    2. Use a drill mounted pump you can get them from a hardware store.
      Thats how i do mine pump the bleach and water solution from a gallon jug.

    3. Some manufacturers (I have a Keystone Montana) recomend you remove the overfill vent cover and pour the bleach in there. They also recommend removing that cover when filling the freshwater tank to prevent air from getting trapped.

    4. It doesn’t have a fill port besides the city water connection? If not then you can get a piece of 2”pvc pipe from a supply store and the proper adapters for the hose, fill the pvc pipe like a mini tank with the chlorine solution.

  3. Attach the white water hose (mine is 25ft) to the Rv fresh water intake valve. Pour the diluted bleach into the other end (unattached) of the white hose (make sure the unattached end is higher than the end attached to the RV. Then attach the hose to the fresh water faucet and turn it on. This allows the bleach solution in the hose to flow into the tank.

    1. Hi Frank, I believe it varies from manufacturer to manufacturer, I’d check your owner’s manual or contact a Camping World service center.

    2. Don’t turn on the water pump until the water tank is full with the correct ration of bleach. You don’t want to run a concentrated solution through the water lines.

  4. The first step on this is to turn the water heater off; but on another video, they said to turn off certain valves for the water heater. Can this simply be done by the inside indicator panel ensuring the water heater is off? Is that sufficient enough for having the water heater off when sanitizing the fresh water tank?

    1. No that won’t keep the bleach water out of you hot water heater. You have to bypass the hot water heater, by doing that water is not going into the water heater.

  5. I started the process , got the bleach solution in & circulated through the entire system, but was interrupted before emptying the bleach solution from the holding tanks. Does it hurt anything to leave the solution in the tanks and not flush the system for a few days?

  6. I have a sulfur and rotten egg smell in my fresh water system. Will this process with bleach take care of that and should I pump this bleach mixture through my water heater also?

  7. When draining the water, do I drain the grey water tank once I run the water through or if I still smell bleach, do I drain the fresh water tank

  8. The bleach water will not go into the fresh water tank through a funnel. How do I get the bleach water into the freshwater tank?

  9. I just bought a ’97 Itasca. It has issues, and one of them is that when I run the water faucets, foam or suds come streaming out. What up? Di the previous owner try to clean the system with soap? Does not look potable. Referring to the article above, can I just keep flushing the system util the suds go away?

    1. RV/Marine antifreeze in the system looks like pink foam when you rinse the system clean. (previous owners “winterized” the system)

    2. I had this issue also! My problem was a white milky and foaming water coming out of my taps.
      The problem was I would let my rig sit without draining the water . This sitting water in my water heater was dissolving the anode rod which caused the milky foam coming out of my tap.

  10. Yes it’s true. But far more worrisome is bacterial growth in your system. As long as you don’t overdo the bleach (make a solution as instructed above) and let it sit at least 3 hours before draining and flushing ( you can go longer but I would not go over 24 hours if possible) your system should be fine.

  11. I have a new trailer- first time. Do I need to flush out the antifreeze in the lines before adding the bleach water?

    1. I would recommend doing so. That will allow the bleach to do it’s job better and won’t cause any concerns with mixing bleach and antifreeze (I don’t know if that would be a problem or not, but best to avoid doing it).

  12. I was told to use vinegar, not bleach. Anyone done this and what is the ratio to use. Also how long to keep in the tank?

  13. I do mine every spring and just completed the process. These instructions are for a winterized RV. Don’t make this harder than it is. To get rid of the RV antifreeze, first, I hook up the hose to the city water connection. Turn on the hose to pressurize the system. Inside open all the faucets and shower head, I even do the toilet. Once the antifreeze is purged from the system, I fill the onboard water tank with water (100 gals). At the same time, I pour approximately a pint of bleach in the side water fill. (Mine doesn’t have a check valve). Once the system is full, I remove the hose from the city water connection and turn on the water pump and again open all the faucets, shower and toilet to circulate the bleach water. Let sit 12-24 hours. Dump, refill, circulate and dump. I do this twice. Don’t forget to make and discard several batches of ice if your RV is so equipped. Also, if you have a washer, run the first load with an old towel or similar as it will most likely have some residual antifreeze trapped in the line. I learned from my mistakes. I hope you don’t have to. Have a great season!

  14. I left water sitting in the Grey tank for about 2 years without using it and I am concerned it has a lot of bacteria or algae. Will this work to get it cleared up. I don’t even want to run it thru my system. Just get it cleaned up and dump it.

  15. Your “grey” tank is waste water from your sinks and shower. So if you are talking about your “grey” tank and not your “fresh water” tank I would not worry that much about it. Just fill it and flush it a couple of times with a light detergent and water mixture. But if you are talking about your “fresh water” tank it’s a different story.

  16. Once we drain the bleach and refill to get the bleach out
    Do we drain tank completely or leave some water in tank even if we are not using rv at that time?

  17. When you say “drain” or “empty” the fresh water tank after running water though the system and letting is sit, do you drain through the low point valve under the trailer or just continuously run the pump and water through the faucets until tank is empty? Thanks.

    1. Run the water pump and drain the tank through the system to clear the bleach out of the lines as well as the tank.

  18. I have a 93 Itasca Sundancer. I don’t have the availability to bypass my water heater. Will the process be ok with the water heater.

    1. I’ve been told as long as it’s not a tankless water heater it’s fine. In fact my Rockwood owners manual and supplementary videos make no mention of bypassing a regular water heater. However if you retrofitted a tankless water heater I do believe you need to bypass it.

  19. We have never used the fresh water tank. This is our 4th summer with our RV. Should we do this only when we want to use the fresh water tank?

    1. Hi Kathy, Remember that hot, warm dark and humid conditions are perfect breeding spots for mildew and bacteria to grow, so the more you sanitize and disinfect the better you are. I believe the warmer climate requires you sanitize more often. Remember, your fresh water tank has a overflow valve or opening near the top two inches of your holding tank so your filling the tank still is not adequate, you need to drive around and swish the water, I do my Monaco’s 100 gallon tank with only 20 to 30 gallons of water and the swishing gets it all and including the top of the fresh water tank and I have not wasted 100 gallons of water.

  20. We sanitize the tank after we drain the tank of antifreeze when we open the camper in the Spring. How often do you recommend sanitizing during camping season? We usually camp May- October.

  21. I live in an apartment complex without access to an outside water outlet, nor any place to dump. Any ideas where I can do this process? It seems a little inconvenient to do this in the middle of a camping trip.

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