How much bleach to sanitize RV water tanks depends greatly on a number of different things about your RV.

From the size to what kind of problem you’re trying to eliminate, there are multiple things to keep in mind when sanitizing your RV water tank.

The right amount of bleach will vary, but the general rule is that one cup is good enough for a water tank with a capacity of 40 to 60 gallons. Depending on how foul your tank is, or if you want to kill everything possible, you may want to increase this amount.

You want the assurance that your water system is safe to use, especially during summers when the risks of bacteria and contamination goes up.

We tested out different quantities of bleach to see what worked, and researched what other RV owners had to say on the topic. We’ve collected our recommendations together in one place.



Why Do You Need to Sanitize In the First Place?

Sanitizing a dirty RV tank would make sense, to get rid of any potential risks, but what about brand new tanks, or tanks that simply haven’t been used in a while? Many might think a simple rinse is enough before you can use your RV tank again.

But there are plenty of reasons sanitizing is essential.

When you leave your RV in storage, there is a very high possibility that bacteria have settled and built up in your water system. Not just in the walls of your tank, but also the piping system. The best way to get rid of them is to sanitize the entire system with bleach.

These bacteria, if not removed, can end up contaminating the water you add in, especially if you’re drinking it. Contaminated water can cause problems like gastrointestinal issues, diarrhea, dehydration, etc. Keeping the water system sanitized helps prevent these issues.

Stale water in the tank can also result in unpleasant smells. By sanitizing, you can get rid of these odors so that any fresh water you add in will not retain these smells.

How Much Bleach to Sanitize Your RV Water Tank?

Most RV owners and users will recommend using one cup of bleach for every 40-50 gallons of your water tank capacity. So, if you have a water tank of about 40 gallons, one cup of bleach is enough. If its capacity is 100 gallons, two cups are enough. If the tank is smaller, and has a 20 gallon capacity, half a cup is enough.

Some RV-ers will recommend going lighter and using less bleach, for example, one cup per 60 gallons. Others will recommend stronger, but this really depends on the tank. If you want the absolute surety that your tank is sanitized and using less bleach makes you anxious, you can go for a stronger solution.

Is Too Much Bleach Bad For The RV?

No, the likelihood of harming your RV’s water system by using more bleach is very low. In fact, when using bleach for sanitizing, you’ll be leaving the solution in the tank for a number of hours, and not days. Since bleach sits on the shelf in plastic containers for months on end, you can be sure it’s not likely to harm your water system in a few hours’ time.

If you think you’re not using enough bleach, even two or three cups per 50 gallons is fine, and you won’t be harming your system in any way.

On the other hand, if you’re worried about accidentally ingesting any leftover traces of bleach, you can flush out your tanks several times or until you can no longer smell the bleach for your own peace of mind. However, this is not likely to cause any issues.

If you’re going by smell, it may take quite a few rinses and flushes before it is removed completely. While the smell of bleach lingers, the chemical itself gets washed away pretty fast, so you have little to worry about.

How Do You Know You’re Using Enough Bleach?

So, there’s no such thing as ‘too much’ bleach, but what about ‘too little’?

In reality, there is no such thing as ‘too little’ either. The purpose of bleach is to sanitize the water system, but you can’t eradicate every possible threat that exists. In the first place, you’re not trying to have absolutely pure water anyway, you’re just trying to make the water safe to drink.

Even our water systems at home don’t have 100% clean water, but it is water that is safe and won’t make you sick. Therefore, the amount of bleach you add is entirely up to you.

Plenty of RVers will actually add a teaspoon or so of bleach to the water tank when they fill it with water. At this low level, bleach is actually safe to ingest, since it’s spread throughout the water and becomes extremely diluted. Some water districts and swimming pools also add bleach to the water to get rid of certain pathogens, so if you’ve ever been to any of these, you’ve probably already ingested some amount of bleach.

Therefore, for a regular water system, you can add any high or low amount of bleach with the same end result.

However, if you know that your water tank is heavily polluted, then you should use more bleach to get rid of the contamination and any possible pathogens. Since the water is already polluted, you definitely don’t want to ingest anything in it. In such cases, you should add a cup or two of bleach and leave it for several hours to sanitize it properly.

How Long Should You Leave Bleach In Your RV Water Tank?

How long you should leave the bleach in depends on the size of the tank and how much bleach you used in said tank. If you’ve used only a small amount of bleach, you may have to leave it longer, whereas for larger amounts, you can drain faster.

In either case, you should be leaving it in for at least eight to twelve hours. If you’re going for the one cup per 40 gallon approach, eight hours is plenty. For lesser amounts of bleach, you may have to go up to twelve or more.

How To Know When To Sanitize Your Water Tank?

The best way to figure out if your tank water is clean is to get some of the water from it and check. Don’t drink it immediately, since you don’t know if it’s safe for drinking or not. Even a sip to taste test can be dangerous if there are any harmful pathogens in the water.

Hold the water up to light and see if it has any color. Hazy, green or yellow-ish water is a sign that your tank is not clean and should be sanitized. Besides that, if the water doesn’t smell right and has a stale or foul odor, it’s time to sanitize.

White water can be aerated, which means that the air in the lines may have gotten trapped. By leaving it for a few minutes, you can get rid of the air bubbles and then check for smell or color.

If your water tank is really foul, then you may have to remove it and clean it out by hand. In fact, for very dirty tanks, even cleaning isn’t a great solution and you may just end up having to replace the whole thing entirely.

The right amount of bleach to be used for RV water tanks depends on multiple things. The general rule of thumb though, is that one cup, give or take, for every 40-60 gallons of water is a good enough amount and will get the job done well enough.


Anthony Day

Anthony Day

Hi, my name is Anthony, and RVs are what I'm passionate about. I bought my first RV when I was 21, and I've been hooked ever since. I'll guide you on how they work, how they can be used in different environments, and how they fit into our everyday lives.

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