Learning how to drain an rv fresh water tank is one of those chores that feels a bit intimidating the first time you do it, but honestly, it's one of the simplest parts of being a rig owner. Whether you're getting ready to put your camper into storage for the winter, trying to shave off some weight before a long haul, or just realizing that the water in your tank has started to smell a little bit like a swamp, knowing the right steps will save you a lot of headache.
It might seem like you just pull a plug and walk away, but there's a little more to it if you want to make sure the system is actually empty and ready for whatever comes next. If you leave just a little bit of water in those lines during a freeze, or let old water sit and grow algae, you're looking at a much bigger project down the road.
Why you need to keep that tank empty
Most people don't think about their fresh water tank until they're actually using it, but it's probably the most important part of your plumbing system. Think about it: that's the water you're using to brush your teeth, wash your face, and maybe even cook with.
One of the biggest reasons to drain the tank is simply weight. Water is heavy—about 8.3 pounds per gallon. If you have a 50-gallon tank that's sitting full, you're hauling over 400 extra pounds down the highway. That's a lot of unnecessary strain on your engine and a big hit to your fuel economy. Unless you're planning on boondocking in the middle of nowhere immediately, there's really no reason to carry that extra bulk.
Then there's the "stale water" issue. If water sits in a plastic tank in a warm environment for more than a couple of weeks, it starts to get funky. Bacteria love those conditions. Draining the tank regularly ensures you aren't letting anything nasty take up residence in your plumbing.
Finding your drain valves
Before you can actually start the process, you have to find where the water actually exits the vehicle. Every RV is a little different, but most follow a similar logic.
Usually, you're looking for a white plastic valve or a "petcock" located underneath the chassis, roughly in the area where your fresh water tank is mounted. On some travel trailers, it's just a simple plug you unscrew. On bigger Class A motorhomes, you might find a dedicated valve inside one of the service bays, often labeled clearly (if you're lucky).
You also need to look for your low point drains. These are different from the main tank drain. These are two pipes—usually one red and one blue—that stick out from the bottom of the RV. These drain the actual hot and cold water lines throughout the camper, not just the tank itself. If you want a truly empty system, you have to open these too.
Step-by-step: How to drain an rv fresh water tank
Alright, let's get into the actual steps. It's not rocket science, but doing things in the right order makes it go much faster.
- Turn off the water pump. This is the golden rule. You never want your water pump running when there's no water to move. If you leave it on while the tank is empty, it'll just keep spinning and eventually burn itself out. That's an expensive mistake you don't want to make.
- Disconnect from city water. If you're at a campsite and plugged into a hose, turn that off and disconnect it. You can't drain a system while you're still pumping water into it!
- Open the main drain valve. Go ahead and twist that valve or pull the plug. You'll hear the water start to gush out. If it's just a slow trickle, don't worry—we'll fix that in the next step.
- Open your faucets and the low point drains. This is the secret to a fast drain. By opening the faucets inside your RV (the kitchen sink, the bathroom, even the shower), you're breaking the vacuum. It's like putting your finger over the top of a straw; the water stays in until you let air in. Opening the faucets allows air to push the water out much faster.
- Level the rig. If your RV is tilted away from the drain, you're going to have a gallon or two of "puddle" water left at the bottom of the tank. Use your leveling jacks or blocks to tilt the RV slightly toward the side where the drain is located.
- Patience is a virtue. Depending on how big your tank is, this could take anywhere from ten minutes to half an hour. Go grab a coffee or start packing up your gear while it does its thing.
Dealing with the water heater
While you're learning how to drain an rv fresh water tank, you might wonder if you should drain the water heater too. The answer is: it depends.
If you're just freshening up the water for a new trip, you can probably leave it. But if you're winterizing or if the water has been sitting for months, you absolutely need to drain the heater.
Pro tip: Never, ever pull the drain plug on a water heater while the water is hot or the system is under pressure. You'll end up with a face full of scalding water. Turn it off, let it cool down, and pull the pressure relief valve at the top before you touch that bottom plug.
What if the water won't come out?
Sometimes you open the valve and nothing. Or maybe just a pathetic little drip. Usually, this happens because of sediment. Over time, minerals and "gunk" from various water sources can settle at the bottom of your tank and clog the drain hole.
If this happens, you can usually fix it with a small piece of wire or even a quick blast of compressed air into the drain line to dislodge the debris. Just be careful not to push anything too far back in where it can cause a permanent blockage.
Another common issue is that people forget the "vacuum" part I mentioned earlier. If all your windows and doors are shut and the faucets are closed, the water literally doesn't have the air pressure behind it to move. Open those taps!
Sanitizing after the drain
Draining the tank is only half the battle. If you've drained the tank because the water smelled like rotten eggs, simply refilling it isn't going to fix the problem. The bacteria are still clinging to the walls of the tank.
Once the tank is empty, it's the perfect time to run a bleach solution through the system. A general rule of thumb is a quarter-cup of household bleach for every 15 gallons of tank capacity. Mix it in a gallon of water first, pour it into the tank, fill the rest with fresh water, and let it sit for a few hours.
After that, you'll need to do the "drain and refill" dance a couple more times to get the bleach smell out. It's a bit of a process, but it's better than drinking funky water.
Wrapping things up
It's easy to get caught up in the fun parts of RVing—picking the destination, setting up the campfire, or finding that perfect lakeside spot. But the "boring" maintenance stuff, like knowing how to drain an rv fresh water tank, is what actually keeps those trips from turning into nightmares.
Once you've done it once or twice, it'll become second nature. You'll find yourself doing it as part of your standard breakdown routine at the end of every trip. Your RV will be lighter, your water will stay fresher, and your plumbing system will thank you for it in the long run. Just remember: pump off, valves open, and let gravity do the heavy lifting. Safe travels!