Learning exactly how to empty fresh water tank in rv setups might seem like a no-brainer, but there are a few tricks to make sure you get every last drop out without making a huge mess or damaging your plumbing. Whether you're getting ready to put the rig into storage for the winter, trying to shed some weight before a long mountain climb, or you just realized that water has been sitting in there for three months and probably smells like a swamp, knowing the right way to drain it is essential.
It's one of those chores that becomes second nature after you've done it a few times, but the first time can be a bit confusing if you aren't sure where your valves are hidden. Every RV is a little different, but the general mechanics of the plumbing systems are usually pretty similar.
Why you need to drain the tank regularly
Before we get into the "how," let's talk about the "why" for a second. You might think, "Hey, it's just water, why can't I leave it in there?" Well, for one, water gets stale. If it sits in a plastic tank in the summer heat, it can start growing algae or bacteria, and nobody wants to brush their teeth with that.
Then there's the weight factor. Water is surprisingly heavy—about 8.3 pounds per gallon. If you have a 50-gallon tank that's full, you're hauling over 400 pounds of dead weight. That kills your fuel economy and can make your trailer or motorhome feel a bit more sluggish on the road. Finally, there's the winter issue. If you live somewhere where it freezes and you leave water in the tank or lines, you're looking at cracked pipes and a very expensive repair bill come springtime.
Finding your drain valves
The first step in how to empty fresh water tank in rv units is actually finding the exit point. Most RVs have two different types of drains you need to worry about: the main tank drain and the low point drains.
The main tank drain is usually a larger valve located directly underneath the fresh water tank. It might look like a simple plastic turn-cock or a white T-handle. If you look under your rig, you'll usually see a small white or clear hose poking out of the underbelly; that's your target.
The low point drains are a bit different. These are the lowest points in your entire plumbing system (hot and cold lines). There are usually two of them—one for the hot side and one for the cold. You'll want to open these to get the water out of the actual pipes, not just the tank itself.
Step-by-step to a dry tank
Once you've spotted your valves, the process is pretty straightforward, but doing things in order helps it go faster.
- Turn off the water pump. This is the big one. If you leave your pump running while the tank is empty, it'll just keep sucking air and could eventually burn out the motor. Make sure that switch is in the "off" position before you start.
- Turn off your water heater. If you plan on draining the whole system, including the hot water lines, make sure your water heater is turned off (both electric and gas) and has had time to cool down. You do not want to drain a hot water heater while the element is on or the water is scalding.
- Open the main drain valve. Go outside and turn that valve. You'll hear the water start to gush out. If you're at home, try to make sure you aren't parked on a spot that will turn into a mud hole.
- Open the low point drains. These usually have screw-on caps or pull-valves. Once you open these, you'll see more water start to trickle out.
- Head inside and open the faucets. This is a pro tip that a lot of people miss. By opening your kitchen and bathroom faucets (and the shower), you break the vacuum in the lines. It's like putting your finger over the top of a straw—if there's no air coming in, the water won't want to come out. Opening the taps lets air in and lets the water flow much faster.
- Flush the toilet a few times. This helps clear out the small amount of water sitting in the toilet valve and the line leading to it.
Dealing with the water heater
While you're figuring out how to empty fresh water tank in rv systems, don't forget the water heater tank. This is separate from your main fresh water tank. Most water heaters hold 6 to 10 gallons of water.
To drain this, you'll usually need to go to the exterior access panel of the water heater. There's typically a drain plug or an anode rod at the bottom. You'll need a socket wrench to unscrew it. Warning: Stand to the side when you pull that plug, because the water will shoot out with some force, and if it's still warm, it can be messy.
If your RV has an anode rod (common in Suburban heaters), this is a great time to check if it's been eaten away. If it looks like a thin wire, it's time to replace it.
The waiting game
Depending on how big your tank is and how much water is in it, it could take anywhere from ten minutes to half an hour to fully drain. It's not a fast process. I usually open the valves and then go inside to do some cleaning or pack up the rest of the gear.
Once the water stops dripping, don't just close everything up immediately if you're winterizing. Some people like to leave the valves slightly open during storage to allow for expansion, though most prefer to close them to keep bugs from crawling up into the plumbing. If you're just refreshing the water for a new trip, you can close them as soon as the flow stops.
Sanitizing after you empty
Emptying the tank is only half the battle. If you've emptied it because the water smelled a bit funky, you'll want to sanitize it before you fill it back up.
A simple mix of a quarter-cup of household bleach for every 15 gallons of tank capacity usually does the trick. You mix the bleach with water in a gallon jug, pour it into your gravity fill (or use the winterizing siphon on your pump), and then fill the tank the rest of the way with fresh water. Let it sit for a few hours, then—you guessed it—follow the steps above to empty it all over again. Rinse it once more with fresh water, and your system will be clean and safe.
A few common mistakes to avoid
One of the most common mistakes people make when learning how to empty fresh water tank in rv units is forgetting the outdoor shower. If you have an exterior wash station, make sure you open those valves too. Water loves to hide in that hose, and it's often the first thing to freeze and crack in the winter.
Another thing to watch out for is your water filter. If you have an onboard filtration system, you'll want to remove the filter cartridge before you drain everything, especially if you plan on using any cleaning agents or if you're blowing out the lines with compressed air.
Lastly, don't forget the "burp." Sometimes air gets trapped in the lines when you're refilling after a total drain. When you finally fill the tank back up and turn the pump on, the faucets might sputter and spray for a minute. That's totally normal—it's just the air being pushed out.
Wrapping it up
Knowing how to empty fresh water tank in rv plumbing is a fundamental skill that keeps your water fresh and your pipes intact. It's not a glamorous job, and you might get your hands a little wet, but it's the best way to ensure your next trip doesn't start with a face full of stale-smelling water. Just remember to find those low point drains, open the faucets to let it breathe, and always, always turn off that pump first. Happy trails!