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What to Do When Your RV Fresh Water Tank Won’t Fill

RV owners who love to dry camp or bootleg can attest to how important having a well-filled water tank is. After all, water is essential not just to living, but to living comfortably. Water that you use in your sink and shower comes from your potable fresh water tank. 

When you fill up your tank, though, you might notice that it is filling especially slowly. Or, even worse, that your fresh water tank isn’t filling at all. Without an ample supply of water, your RV trip will be nearly impossible to fully enjoy. 

The things that could be causing your fresh water tank to not fill include improper intake design or improper venting. It could also be a sign that the valves are shut. To remedy the issue, you might have to disassemble part of your undercarriage to assess the hoses to see if they’re sagging or kinked. 

RV Fresh Water Tank Won’t Fill 

Before you head out on any big trip, checking your RV’s water tank should be a top priority. Having an empty water tank can ruin an entire journey, causing you to scramble for a solution. If you take a look at your water tank before you head out and find it isn’t filling, there are a few things that may be to blame. 

Improper Intake Design 

If there’s not enough slope between the fill and the tank, your tank will fill slowly or not at all. You may need to decrease or increase the angle at which your fill hose is arranged at the opening of the tank.  If the line is too long, it could also be slowing down the fill process. 

Shut Valves 

The first thing you should verify is if the valves on your water tank are still on. Valves being shut is one of the most common reasons why an RV fresh water tank won’t fill. Depending on what model fresh water tank you have, there may be several of these valves. Be sure to give each of them due attention; if you can’t find them all, check with your user’s manual. 

If the valves are closed, air can’t escape from the fresh water holding tank while water flows in. Without open valves, the pressure inside keeps more water from entering the tank. 

All that is needed here is to open them back up. It’s a simple solution to a problem that arises fairly frequently. Once you’ve opened up the water valves, try to fill your tank again. It should fill once again. 

Improper Venting 

If you’ve given a thorough check to all of the valves and see that they’re not closed, now is the time to check the vent tubes. It’s not uncommon for these tubes to get bent, kinked, or clogged. Your vent tubes might also not have enough volume for the system you’re using. 


Typically, your vent lines are much more narrow than the fill line. Because of this, they don’t allow for the air to escape fast enough so that a large volume of water can enter the tank. 

If you find that your water tank is burping back out the water, it’s likely an issue with these tubes. If the volume of water that is entering the tank is more than the amount trying to escape, that will cause the ‘burp’. Water escapes back out of the fill, meaning you’re either going to spill water or turn down the faucet’s volume considerably. 

Don’t force water into a slow filling water tank faster than it can vent. Doing so causes the tank to expand, which will result in the straps that secure it stretching or breaking. It could also damage the framing on the tank, or even rupture the tank entirely. 

You can try to look for a venting system with greater volume. This could include finding a tube that is larger in diameter and can allow more air to vent. Be sure that the fittings for the new tubes will match your RV’s model’s fill line. 

Obstructions, Kinks, or Leaks 

You should also keep an eye out for anything clogging your vent tubes. Bugs, leaves, and other debris might find their way into the tubes and cause a blockage. You can use a thin, flexible wire to get these out. 

Be sure that you’re checking for these clogs in the vent hose between the water tank, as well as in the exterior vent. The exterior vent is usually part of the fill assembly, located on one side of your RV. 

As for leaks, this may be trickier to search for. Even the tiniest of cracks can make it so that the tubes will not work correctly. You might be able to create a temporary fix with strong tape like FlexTape or duct tape, but the best course of action is to replace it. 


If you are still finding that the RV water tank won’t fill despite having tried these other fixes, the issue is more than likely due to your hoses. Becoming misaligned or even slightly moved can impact their overall functioning. The best course of action is to realign them. 

To access this, you’ll have to disassemble your undercarriage. Doing so will allow you to analyze and correct your houses, but the process can be difficult. It’s a complicated process that involves a lot of moving parts. 

If you choose to disassemble your water system, you can fix the position of your hoses. Usually, consulting your manual will let you know what their ideal arrangement should be. If you’re not sure you’ll be able to disassemble the tank, call a specialist. 


If your RV fresh water tank won’t fill, you’re likely to want to clear up this problem as soon as possible. Not having water on your trip is nothing short of a crisis, especially for longer journeys. There are a few things that cause an RV water tank to fill slowly, or to not fill at all. 

For one, you might have an incorrect intake design. Check that the slope of your fill hose is even and proper, making adjustments as needed. Secondly, take a look at all of the valves; if they’re shut, that’s a strong contender for the root of your issue. Opening them up will resolve the issue. 

Problems with the vents are also common. Check that they’re the correct volume, and haven’t leaked, bent, or sagged anywhere. If this still doesn’t solve the issue, you might need to get your hands dirty by disassembling your water tank to check the hoses. If they’re out of place, that could be why your tank isn’t filling. 

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