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How to Sanitize an RV Fresh Water Tank

February 10, 2024

The average RV has a fresh water holding tank that can hold up to 100 gallons of water. This is the water that you drink and use to shower, brush your teeth, and cook.

Over time, however, the water can become contaminated and that can lead to costly issues in the long run.

That’s why it’s so important to flush and sanitize the holding tank regularly.

What’s the best way to clean and sanitize an RV fresh water tank? Is it similar to cleaning the gray tank? What products should you use?

For the answers, be sure to keep reading. We’ll be going over everything you need to know about sanitizing the V’s fresh water system below.

How Frequently Should You Clean RV Fresh Water Tanks?

how often should you clean rv freshwater tankAssuming that you’re in the RV full time, it’s best to sanitize the RV fresh water tank once every six months. That will prevent bacteria, mold, mildew, and algae from building up in the water tank and lines, which can lead to bad smells and illness.

There are also specific situations where you want to sanitize the freshwater tank. For example, you’ll want to clean the tank if you’re using it after a long period of storage.

You also want to sanitize the tank after buying a used RV as you’ll have no idea how long water has been inside the tank.

Other situations where you should sanitize the fresh water tank:

  • If the water at your campground was contaminated
  • If your RV has been left sitting unused for at least two weeks with water still in the tank
  • If you filled it with contaminated water from a community

Signs That Your Freshwater Tank Needs Attention

If you notice an unpleasant odor coming from the fresh water tank, chances are, it’s due to bacteria build-up, which will need addressing.

A contaminated tank will also affect the appearance and taste of water so if you notice something is off, that might be why.

In some cases, you may also notice visible sediment coming out from the hose.

How Long Does It Take to Sanitize the RV’s Fresh Water System?

The process itself isn’t complicated; you only need a few supplies but don’t let that fool you – it can easily take half a day to thoroughly sanitize the fresh water tank.

For one thing, you’ll need to drain and fill the fresh tank several times. You’ll also need to let the cleaning solution sit in the tank and water lines for several hours after adding it in.

That’s why many people choose to clean their fresh water tanks overnight. That way, you won’t be wasting valuable time during the day.

What Should You Use to Sanitize the Fresh Water Tank?

There are two options – you can either use a non-scented bleach or an RV fresh water sanitizer. The former will need to be mixed with water to obtain the correct ratio while the latter is a product that’s specifically made to clean and sanitize the fresh water tank.

Never use scented or colored bleach. Remember, this is the tank that will be holding your potable, drinkable water and the last thing you want is to introduce chemicals.

How to Sanitize the Fresh Water Tank In Your RV – A Step By Step Guide

Before you begin, you may want to take a look at the manufacturer’s manual on how to sanitize the fresh water tank in your RV. It may answer any questions or concerns you may have about the process.

Step 1: Shut Down the Water Heater

shut down water heaterStart by turning off the water heater. That way, you won’t have to worry about accidentally heating the bleach solution, which could cause permanent damage to the tank itself.

In most RVs, the switch for the water heater is located outside the RV in a pull-down compartment.

Step 2: Drain the Fresh Water and Hot Water

The drain valve for most RV’s is located directly below the fresh water tank. Open the valve and that will allow you to drain all the remaining water from your fresh tank.

Do the same for the hot water tank. You’ll easily be able to identify the valves as the hot water tank is usually labeled in red while the cold water tank is labeled in blue.

Once all the water has been drained from the tanks, close the valves.

Note: You can skip this step if you’ve already drained the tanks when you winterized your RV.

Step 3: Add the Appropriate Amount of Bleach Into the Fresh Water Tank

low point valvesNever add bleach directly to your freshwater tank – it will damage the holding tank. What you want to do instead is dilute it with water.

First, you’ll have to calculate how much bleach is needed to sanitize the tank. As a general rule, you want to add a quarter cup of bleach for every 16gal of water. That works out to be 1oz of bleach per 8 gallons of water.

Once you’ve measured out the bleach, pour it into a jug, pitcher, or bucket. You can then add it to the fresh water tank.

To prevent the bleach from spilling over the side of your vehicle, it’s best to use a funnel. That will allow you to easily pour the bleach mixture into the fresh water opening.

If you don’t have a funnel, you can create your own using a disposable water bottle. Simply cut part of one side out and leave the mouth intact. You can then put the spout into the freshwater inlet with the cut-out side facing upward and add the bleach solution through the hole on the side.

Alternatively, you can use a small plant watering can – just make sure the spout is small enough so that it fits into the water inlet.

Step 4: Fill the Tank With Clean, Potable Water

Next, fill the fresh tank with clean water. To do this, simply connect the water hose to a clean, fresh water connection.

Assuming that you calculated the right amount of bleach in the previous step, filling the tank will give you the appropriate dilution ratio.

Once the tank is full, place the cap back on the inlet.

Next, turn on the water pump inside the vehicle. Open all of the faucets in the sinks as well as the showerheads, both the cold and hot sides.

fill tank with waterYou want to let the bleached water run through the entire system for a couple of minutes. You should be able to smell the bleach coming out of the faucets while you’re doing this.

Don’t worry if you get a little bit of bleached water into the gray tank.

After the water has run for 2-3 minutes, turn off the faucets and water pump.

Tip: If necessary, you can use an RV water filter when filling your tank – that will give you extra clean water to sanitize the tank.

Step 5: Let the Bleach Mixture Sit In the Tank

Let the bleach mixture sit inside the fresh water tank for at least five hours. For the best results, let it sit in the tank and water lines for 12 to 24 hours (but not more than 24 hours).

Given the amount of time it takes, many people choose to do this step overnight while they’re sleeping. Just remember to save some potable water to drink and cook with in the morning.

Step 6: Let the Fresh Water Drain

Next, you want to drain the system. Make sure not to drain it into the soil if you’re using bleach since it can harm the soil and plant life.

One way to do this is by using a 5gal bucket. Place it under your valves to collect the remaining bleach solution and dispose of it properly in an RV dumping site or sewer inlet.

Alternatively, you can move the water into the grey water tank. Simply turn on the water pump, open the faucets, and let the water flow with the inlet attached to a sewer hookup.

When you’re finished, shut off the water pump. Just remember to reopen the low-point valve afterward – that will let the fresh water tank drain all the way through so that there won’t be any bleach left behind.

Step 7: Refill the Tank With Fresh Water

The last step is to flush the tank with clean water. Simply refill the water tank and let it circulate throughout the system. Make sure to open all faucets, including the shower. For example, you can do this at a fresh water fill station.

Let the water run until there’s no longer a bleach smell. While you’re doing this, you can keep the gray water tank valve open.

Repeat the process. You want to flush the fresh water tank multiple times until all of the bleach is gone. That way, there won’t be any chemicals left over in your potable water.

How to Clean Your RV Fresh Water Tank With a Commercial Sanitizer

There are commercial sanitizers for those who want to avoid using bleach. They are a bit more expensive but are generally easier to use.

Before disinfecting the fresh water tank with a sanitizer, make sure to flush the tank thoroughly with clean water.

Once it’s flushed, measure the appropriate amount of sanitizer. Refer to the instructions on the bottle – most will tell you how much product to use per gallon of water.

Measure the correct amount of sanitizer and pour it into the fresh water tank using a funnel. Next, fill it with fresh water.

Drain a small amount of water from all outlets, including the faucets and showers, and let the solution sit in the tank for at least one hour.

Drain the fresh water tank and lines afterward and refill the tank with fresh, clean water.

Tip: Keep in mind that not all products are formulated to kill bacteria – some may only help with odors.

Tips on Keeping Your Water Lines Clean

Here are a few things to keep in mind if you want to keep your lines clean.

Make Sure to Use the Right Hose

use the right hoseMake sure to use the right hose for potable water. It’s also a good idea to twist and attach both ends of the freshwater hose – that way, you won’t have to worry about any contaminants getting inside.

Invest in an In-Line Water Filter

Using an in-line water filter will eliminate many contaminants from your RV water tank including sediments, chemicals, bacteria, and viruses. For the best results, install it directly at the water source – that will keep your tanks and hose clean.

If you want, however, you can also install it at the end of the hose that enters the RV.

Install an Indoor Water Filter

Using an indoor water filter will prevent contaminants from entering your potable water. They’re also very easy to install as all you have to do is screw it on.

Just remember to change and replace the filters regularly. This is especially true if you’re in an area with hard water as the minerals may clog the filters quickly.

As a general rule, you want to replace them every three months or every camping season.

Using Bleach or an RV Fresh Water Tank Sanitizer – FAQs

How much water does a fresh water tank hold?

how much water does freshwater tank holdAn RV’s fresh water tank holds anywhere from 20 to 100 gallons of water, depending on the model. For example, a large Class-A vehicle will likely have a tank larger than 60 gallons while a small camper holds 20 to 40 gallons of water.

The amount of water that the holding tank is important because it determines how much product you should use – this goes whether you’re using bleach or a commercial sanitizer.

How often should you clean the RV fresh water tank?

Ideally, you want to clean and sanitize the holding tank for fresh water once every six months, assuming you’re in the RV full-time. That will prevent germs and gunk from accumulating inside, which can contaminate your water.

It’s also important to sanitize the tank after winterizing the RV or if you’ve filled up the tank with contaminated water.

How much bleach do I need to disinfect my water tank?

The amount of bleach that you need will depend on the amount of water that is in your tanks.

As a general rule, you want to add 1/4 cup of bleach for every gallon of water or one ounce of bleach for every eight gallons of water.

Never add bleach directly into the fresh water tank as it will be too harsh and can damage the tank materials.

how to sanitize an RV fresh water tank

How long do you leave bleach in a freshwater tank?

For the best results, you want to let the bleach solution sit in your fresh water tank for 12 to 24 hours, before draining and flushing the tank with clean water.

Given how long it takes, we recommend doing this overnight – if you start in the afternoon, it’ll be ready for you when you wake up in the morning.

Just remember not to leave the bleach solution for more than 24 hours.

How do I get the smell out of my RV’s fresh water tank?

Sanitizing the fresh water tank with bleach or a commercial sanitizer will eliminate the odors.

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