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How To Fill Up Your RV’s Fresh Water Tank

A recreational vehicle (RV) consists of three water tanks – black, gray, and the fresh water tank.

Each tank has its use.

The black water holds everything that comes from the toilet.

Everything that goes down the RV’s sinks and shower drain make its way into the gray water tank.

The fresh water tank provides the water you use in the sink, shower, and toilet.

This water is fresh and potable. The fresh water tank size depends on the RV’s size.

It ranges between 15 to 40 gallons.

The larger the tank, the longer you’ll go without needing a fill-up.

When you do need a refill, the following are some how-to and tips to consider.

rv on road at sunset

Know the Water Hoses

Each RV water tank has a purpose and corresponding hose.

Keeping in mind the uses of the other two tanks, never mix up the hoses.

The fresh water hose must always be used for the fresh.

Otherwise, you’re going to need to disinfect the water hose.

The water hose is usually white, sometimes it’s blue.

If you need to mark it, do so as a reminder to yourself.

Find the Intake Valve

Now you’re ready to find the RV’s fresh water tank intake valve.

If you’re not sure, the valve labeled “City Water” is the one you want to use.

Attach the water hose to the corresponding valve.

Then, the other end of the water hose gets attached to the water spigot.

If you’re staying at a campsite that provides water access, you won’t need to fill up the fresh water tank.

You’ll have the ability to receive water directly from the local supply.

This is a nice perk worth enjoying.

At the campsite, hook up the water hose to the intake value.

The other end gets attached to the local water spigot.

The difference is that you’ll pull the intake valve lever to the correct setting.

The intake valve’s lever should allow you to select the fresh water tank or local supply.

If your RV has this mechanism, be sure to select the correct option.

Monitor the Water Level

It’s a good idea to be aware of the current water level in your fresh tank.

Your RV consists of water level monitors.

The downside of those monitors is that they’re not always accurate.

Some RV models allow visual access to the water tanks.

Before opening the water spigot, it’s a good idea to visually see how much water is currently in the tank.

If you’re heading off to a remote area for a few days, you don’t want to run out of fresh water.

Given that you’re heading out to an area that doesn’t provide local water access, you’re probably OK with roughing it.

Others should ensure that the fresh water tank has enough water before continuing the trip.

When getting a visual read on the amount of water in the fresh tank is not an option, take a look at the RV’s indicators on the panel.

This gives you an estimate.

Water Weight

The only reason you want to avoid filling up the RV’s fresh water tank to the top is the weight.

Water is heavy.

A gallon of water weighs just over eight pounds.

If you multiply that by 15 gallons or 40, you’ll realize that it puts extra weight on the RV.

If you’re traveling light, it might not be a big deal.

It might be more of a consideration for those who have loaded the RV with heavy camping equipment.

Planning helps you make the best choice.

If you’re only going to use the water to shower a couple of times, wash dishes, and use the bathroom, ¾ of the entire tank might be suitable.

Since the water is potable, you can drink it, too.

This may only add a few gallons to the total that you’ll need for the trip.

When you return from your trip, you’ll have less fresh water in the corresponding tank.

But you’ll have an equal amount plus more weight in the other ones.

This weight impacts how well the RV can climb hills and get through the terrain.

So, it’s worth keeping in the back of your mind.

Relieve the Tanks

Some campsites do have dumping stations where you can relieve the black and gray water tanks.

To clean out these tanks fully, it’s best if they’re full.

This helps them flush out.

Once you return home, decontaminate them.

In the meantime, relieving some weight helps the RV move at a better speed.

Start Filling

With the water hose hooked up to the intake valve and water spigot and your knowledge of the fresh water tank’s current level, you’re ready to start filling it.

The process can take as little as 10 minutes.

Outdoor experts estimate that it takes 15 seconds for one gallon of water to enter the tank.

If you’re filling up a 15-gallon fresh water tank, you still have enough time to gauge the water level.

If the tank takes 10 minutes, stay nearby the water spigot.

You want to be there before the fresh water tank gets anywhere near full.

Experts don’t advise you to top off your car with gasoline because the gas can find its way into other components of the car.

Overfilling the fresh water tank has worse consequences.

The weight can cause the rest of the RV to lift off the ground.

There could also be damage to the frame.

If the tank becomes too full, you can always drain some water before leaving the water filling station.

After shutting off the water spigot, leave the intake valve on “tank fill.”

Go ahead and remove the water hose.

To avoid cross-contamination, storing the fresh water hose in a separate area away from the other hoses is best.


Filling up an RV’s fresh water tank only requires a few simple steps.

Remember to use a designated hose and monitor the water level as you fill up.

Then, you’re on your way to your destination.

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