If you're wondering how to sanitize an rv fresh water tank, you've probably noticed a bit of a funky smell coming from your kitchen sink or perhaps you just realized it's been a few years since you actually cleaned the thing. It's one of those maintenance tasks that's easy to put off until the water starts tasting like a garden hose—or worse, like a swimming pool's science experiment. Keeping your water system clean isn't just about getting rid of weird smells, though; it's mostly about making sure you aren't brushing your teeth with a mouthful of bacteria.
The good news is that you don't need a degree in chemistry or a truckload of expensive equipment to get the job done. With some basic household bleach and a little bit of patience, you can get your water system back to tip-top shape in an afternoon.
Why Bother Cleaning Your Tank?
You might think that because you're always putting "clean" water into your RV, the tank stays clean by default. I wish that were the case. In reality, that dark, plastic box sitting under your rig is the perfect playground for algae, mold, and various types of bacteria. If your RV sits for a few weeks with even a little bit of water in it, things can get gross pretty fast.
Even if you're using a high-quality water filter at the spigot, those filters don't stop everything. Eventually, a biofilm—basically a thin layer of slime—can build up on the walls of your tank and inside your PEX lines. If you start smelling rotten eggs or a musty odor when you turn on the tap, that's your RV's way of telling you it's time for a deep clean. Plus, if you ever fill up at a campground with questionable well water, you might be introducing all sorts of microorganisms into your system without even knowing it.
What You'll Need for the Job
Before you start crawling around your service bay, grab a few things. You likely have most of this stuff in your garage or under the kitchen sink.
- Standard Unscented Bleach: Don't get the "splash-less" kind or the stuff that smells like lavender. You want the basic, old-school liquid bleach.
- A Measuring Cup: Precision matters here. Too little bleach won't kill the bugs, and too much will make your water taste like a public pool for the next six months.
- A Clean Bucket: For mixing the bleach solution before it goes into the tank.
- A Funnel: Unless you have a steady hand and don't mind getting bleach on your shoes.
- Fresh Water Hose: Use your standard white drinking water hose, not the green one you use to wash the car.
Doing the Math: Bleach Ratios
This is where people usually get a little nervous, but it's actually pretty simple. The standard rule of thumb is to use one-quarter cup of bleach for every 15 gallons of water your fresh tank holds.
So, if you have a 30-gallon tank, you'll use half a cup. If you're rocking a big 60-gallon tank, you'll need a full cup. If your tank size is some weird number like 43 gallons, just round up slightly. It's better to have a tiny bit more than not enough, but don't go overboard. You aren't trying to dissolve the tank; you're just trying to kill the bacteria.
The Step-by-Step Walkthrough
Once you've got your supplies and your math figured out, it's time to get to work.
1. Drain the System
First, you need to get rid of whatever old, stale water is currently hanging out in your system. Open your fresh water tank drain valve and let it rip. While that's draining, go inside and open all your faucets—hot and cold—including the shower and the outside shower. This helps the water drain faster by breaking the vacuum. Also, make sure your water heater is turned off and cooled down before you drain it. If you have an inline water filter, take the cartridge out now. You don't want to run bleach through a carbon filter because it'll just ruin the filter and soak up the bleach you're trying to use to clean the lines.
2. Mix Your Solution
Don't just pour straight bleach into your gravity fill. It's way too harsh on the seals and can cause damage. Instead, take your measuring cup and pour your calculated amount of bleach into a gallon or two of fresh water in your bucket. Stir it up a bit (carefully!) so it's well-diluted.
3. Fill the Tank
Use your funnel to pour the bleach-water mixture into your fresh water fill. Once that's in, hook up your hose and fill the rest of the tank with fresh water until it's completely full. You want the water to reach the very top so the ceiling of the tank gets sanitized too.
4. Circulate the Water
Now you need to get that chlorinated water out of the tank and into the rest of the plumbing. Turn on your RV's water pump and go to every faucet in the rig. Run the cold and hot water at every sink until you can clearly smell bleach. Don't forget the toilet and the outside shower! Once you smell that "pool" scent at every outlet, shut the faucets off. The goal is to have that sanitized water sitting in every inch of your pipes.
5. Let It Sit
This is the part that requires the most patience. You need to let that mixture sit in the system for at least four hours. If your tank is particularly nasty or hasn't been cleaned in years, letting it sit overnight (about 12 hours) is even better. Just don't leave it in there for days on end, as bleach can eventually start to wear down rubber seals if left in high concentrations for too long.
Flushing the System
Alright, your four to twelve hours are up. Now comes the most tedious part: getting the bleach out.
Drain the fresh water tank completely again. Once it's empty, fill it back up with fresh, potable water. Turn on your pump and run all the faucets again. You're going to smell a lot of bleach at first. Keep running the water until that smell starts to fade.
Most people find they need to fill and drain the tank at least two or three times before the water tastes and smells normal again. It's a bit of a process, but you really don't want your morning coffee tasting like Clorox.
Getting Rid of the Bleach Smell
Sometimes, no matter how much you flush, that lingering chlorine scent just won't go away. If you're struggling with this, there's an easy fix: baking soda.
Mix about a cup of baking soda with a gallon of fresh water, pour it into your tank, and fill the tank the rest of the way with fresh water. Circulate it through the lines, let it sit for an hour or so, and then drain it. Baking soda is amazing at neutralizing odors and will usually knock out that last bit of bleach smell. Some people use white vinegar for this, but vinegar can be a bit aggressive on certain types of plumbing seals, so I usually stick with baking soda.
When Should You Do This?
Ideally, you should sanitize your system twice a year. Once in the spring when you're getting the rig ready for the season, and once in the fall before you put it away (or if you're a full-timer, just every six months).
You should also do it anytime the RV has been sitting unused for more than a month. Stagnant water is a breeding ground for all sorts of stuff you don't want to deal with. Also, if you ever accidentally fill up from a source that looks or smells "off," go ahead and run a sanitization cycle just to be safe. It's much cheaper than a trip to the doctor for a waterborne illness.
A Few Extra Tips to Keep Things Fresh
To make your life easier between cleanings, try to use a dedicated drinking water hose and keep the ends screwed together when you aren't using it. This prevents bugs and dirt from getting inside the hose. Also, using an external water filter—even a basic blue inline one—can help keep sediment and some chlorine out of your tank in the first place.
Another thing to keep in mind is your water heater. If you have a traditional tanked water heater, it can collect a lot of sediment. While you're sanitizing the system, it's a great time to use a water heater flush wand to spray out any calcium buildup that's settled at the bottom.
Learning how to sanitize an rv fresh water tank isn't exactly the most exciting part of RV ownership, but it's definitely one of the most important. Once you get the hang of it, it becomes just another part of the routine—like checking your tire pressure or clearing the slide-outs. Your taste buds (and your stomach) will definitely thank you next time you're out in the middle of nowhere enjoying a cold glass of water.