RV fresh water tank problems can be a real hassle. All RVers (boondockers especially) need access to clean, fresh water to drink, bathe, cook, wash dishes, etc… even if we’re camped in the middle of the desert. But like anything else, your RV’s fresh water tank can develop issues over time.
Whether you’ve got a bad fresh water smell, a leaking tank, or failed sensors, we’ve got the solutions to your RV’s fresh tank woes in this post. Even if your fresh tank is in perfect condition today, this is a great one to read and bookmark so you’ll be prepared if a problem arises.
What Is an RV Fresh Water Tank?
RVs generally have three separate holding tanks, one each for fresh water, gray water, and black water. The RV gray water tank holds water that drains from sinks and indoor showers, while the RV black water tank holds waste from your toilet(s).
An RV fresh water tank holds clean water for use when you’re camping off the grid or traveling down the road. Using a hose designed to be drinking water safe, fresh water is fed into this tank for holding and transporting. Your RV’s plumbing system includes a 12V water pump which is responsible for delivering water from this tank to your sinks, shower, and toilet(s).
Your RV has a 12V water pump that is responsible for delivering water from the fresh tank to your rig’s sinks, shower, and toilet(s).
By contrast, when you’re camping at an RV park or campground with a water spigot at your site, you can hook your fresh water hose to your RV’s city water connection. This allows pressurized water (no pump needed) to be fed into the RV’s plumbing system for use at all taps (sinks and showers) and the toilet(s), giving your rig a continuous supply of fresh water… without pulling water from the onboard fresh tank.
However, when you’re off the grid – whether you’re on the road traveling or you’re out boondocking/dry camping – you still need a source of water. Your fresh water tank is that source.
NOTE: For more details about the difference between onboard and city water, see our post on the fresh water connection vs city water connection. Also, never connect to a city water source without using a pressure regulator.
Unfortunately, through use and time, an RV’s fresh water tank can develop problems.
Common RV Fresh Water Tank Problems & Solutions
Here’s a look at some things that can require your attention in order to keep your RV’s fresh water tank working like new.
Bad Odor or Taste
Unlike a sticks & bricks house, RVs take on water from many different sources that can vary from fantastic to pretty awful. This increases the chances that, sooner or later, you’ll add water into your tank that doesn’t smell or taste very good. That said, even the best-tasting water ever can go bad after it’s been added to the tank.
Bad odors or taste can really ruin your RVing experience!
If your RV’s fresh water tank has a bad odor or the water doesn’t taste quite right, it could be because the water has been in the tank for too long. However, if a recently filled fresh water tank is giving off an odor or the water tastes bad, it’s time to give the tank a good, thorough cleaning and perhaps change your RV water filter. For instructions on proper sanitization, see our post on how to sanitize your RV water system.
For additional details, see our posts “How Long Can You Keep Fresh Water in Your RV Tank?“, and “What to Do If Your RV’s Fresh Water Smells Like Rotten Eggs“.
You can also choose to use a water treatment or freshening product. While we’ve always used the sanitizing method linked above, some RVers prefer a product like these for regular water treatment:
- MAINTAINS DRINKING WATER QUALITY: Star brite AQUA Water Treatment & Freshener ensures perfect drinking water quality in boats and RVs
- PREVENTS FOUL TASTING WATER: Effectively prevents foul tasting or smelling potable water, providing a refreshing drinking experience
- Freshens your freshwater tank and system
- Eliminates Taste & Odor issues from tanks & supply lines
If the water from your fresh water tank has a bad taste, in addition to sanitizing the system you may also want to change your RV water filter. For more on this topic, see our post on how long an RV water filter lasts.
Tank Sensors Not Reading Correctly
RV tank sensors usually give you three or four different readings. You can expect to know when the tank is full or empty along with fill levels in increments of ⅓ or ¼ of the tank’s capacity. Each one of these sensors is in or on the tank’s sidewall. The ¼ or ⅓ full sensor is found closest to the tank’s bottom while the full sensor is at the top. When the liquid in your tank reaches a particular level that sensor is activated, which in turn lights the corresponding indicator light on your monitor panel.
While misreadings may be more common in gray and black tanks due to the contents of those tanks, fresh water tank sesnsors can fail also. Even when sensors in all three types of tanks are working as designed, the ¼ or ⅓ readings are fairly approximate. For example, if your tank is reading ⅓, did it juuust drop below the ⅔ level… or is it juuust about to click over to read empty? This alone is a drawback to traditional tank sensors, in that it’s difficult to know with very much precision where the level is.
But, inaccurate readings on your tanks can also be the result of a faulty calibration on your monitor panel. Some monitor panels may be able to have their calibration adjusted. The one that came from the factory on our Newmar Mountain Aire had that ability, with small set screws that could be used to adjust the reading for each tank. The following video shows how we calibrated it to read more accurately.
If a sensor has simply failed, it can be replaced with a new one. But even that won’t get around the inherent drawbacks to the 3- or 4-light monitor panels. We solved this problem in our motorhome by installing a SeeLevel tank monitoring system on all three tanks, which works exactly like a linear fuel gauge. Installing one of these will guarantee you’ll never wonder where your tank levels are again.
Leaking Fresh Water Tank or Connections
If you’ve got a leak in your RV’s fresh water tank, there are a few things you may need to troubleshoot. First, though, you need to know that most RV fresh, black, and gray water tanks are made of spin-cast or rotocast high-density polyethylene (HDPE). It’s important to know this because HDPE needs to be treated correctly, and you want to use the appropriate solution/technique to repair the crack.
How will you know you’ve got a leak in your fresh water tank? One way or another, leaking water will find its way to the ground, so any time you’re parked on dry pavement and you see signs of a puddle or active dripping under your rig (of what appears to be clear water) means you have a problem. If your fresh water tank is enclosed in a basement area (or behind the coroplast lining beneath your RV), the leak may not even be coming from the area where the tank is located. Water is tremendously skilled at working its way along small spaces to find the lowest point of exit.
Another issue is that access may be the biggest challenge for both diagnosing and repair. With tanks built into enclosed areas during construction, this is a common problem and may take some time to figure out the best route to get to it. Check out our video on RV X-Ray vision for some tips on seeing into enclosed areas.
Once you’ve identified that the leak is coming from the fresh water tank, you’ll then need to determine if it’s a crack in the tank itself or a leak from a fitting.
Crack in the Tank
If you’ve got a crack in the wall of your HDPE fresh water tank, you can patch/seal it using a product like J-B Water Weld or a patch kit specifically designed for HDPE repairs.
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- Patch
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Another product that’s highly-regarded for its ability to repair HDPE is TAP Poly-Weld Adhesive. It claims to structurally bond to the existing plastic, and maintains its flexibility to prevent future failure from vibration/movement of the tank material.
If the crack is especially long, welding may be the preferred repair (though you should be aware that sometimes welding can make the adjacent plastic more brittle, which could lead to another failure down the road).
- UL CERTIFIED - Our Plastic Welder, the factory, and the process have been tested, approved, and Certified by Underwriters Laboratories (UL). Safety is...
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Fitting Leak
The first thing to check is whether the leak is coming from a hose attached to a fitting mounted to the tank. Since connection points in general are a common point of failure, this may be the most likely source of a leak on/near the water tank. If so, tighten or replace the clamp.
If the leak is related to a compromised/broken fitting, you may be able to replace the fitting itself. Fittings can crack due to the cold or simply degrade over time. If the fitting needs replacing, take it to a local hardware or plumbing store and they may have what you need.
Fittings on water tanks are sometimes welded into place, which may require the same sort of product listed above used to repair a crack in the tank itself. Other times, the fittings are simply screwed into/through the tank wall, making them easier to remove and replace.
Again, access may be the biggest obstacle here and may require a fair amount of creativity or professional help.
PRO TIP: Related to fresh water tank problems is a leak somewhere else in the plumbing system. A good warning indicator that there may be a leak in your RV’s fresh water plumbing lines is the sound of the water pump cycling when you’re not running water. Of course, this is only the case when you’re not hooked up to city water (i.e. the water pump is turned on to pressurize the system), and the leak is on the pressurized side of the plumbing (i.e. downstream of the water pump). A water pump that cycles, even occasionally, when you’re not actually running water can be a sign of a leak somewhere in the walls of your RV, and should be investigated promptly to avoid potential water damage (and/or mold problems).
Tank Is Filling Slowly
There are two main types of water fill on an RV. Higher-end rigs often have a valve on the city water input connection that can be turned to either “City Water” (which pressurizes the plumbing system) or “Tank Fill” (which fills the fresh tank). More common is something called a “gravity fill.” This utilizes a separate port on the side of the RV that’s used exclusively for filling the fresh water tank. It’s usually a simple opening with no threads, and cannot be pressurized.
Peter filling the fresh water tank on our first international RV trip in Australia.
A gravity fill also includes a vent line near the filler opening that allows air to escape from the tank as it fills. If this vent becomes blocked for any reason, it could cause the water to back up through the filler neck before the tank is actually full. This can cause two potential problems:
- It can make you think the tank is full when it isn’t
- It can require you to pause filling (to allow the air in the tank to escape) or make you reduce the rate of flow, making the process take longer than it should
If your RV’s fresh water tank is filling slowly, or the water is backing up in the filler neck before the tank is actually full, the most common reason is that the vent line isn’t functioning properly. Your vent hose is located between the fresh water tank and the vent on the exterior of the RV (alongside the filler opening). Locate and trace the vent line (if accessible) and check the line to make sure there are no kinks or obstructions (like dirt/debris or an insect nest) that may have gotten into the vent opening. Straighten the line, or clear any blockage, as needed and air should now be able to escape the tank properly, allowing it to fill more quickly.
With all of the above information, you should be able to troubleshoot the most common RV fresh water tank problems.
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Diane
Friday 5th of September 2025
We just got our camper so we are not real savvy about them. The issue we have is that the water pump comes on every 75 seconds. Not leaking inside but notice a drip from two hoses under the fresh water tank but it only drips when the pump is on. We have a Forrest river salem hemisphere. Is this easily fixable?
TheRVgeeks
Friday 5th of September 2025
Hi @Diane. Sorry to hear about your trouble. The simple answer is "Yes... it should be fixable." But the level of difficulty may vary depending on the actual cause of the problem. If it's a leaking water line (or two), those can be repaired in a number of ways, from wrapping the hole(s) with a plumbing leak repair tape (like this: https://amzn.to/3HVwRFl) to cutting out the damaged section and using a sharkbite fitting (like this one, although you need to check the size of your plumbing lines: https://amzn.to/4n8zAL3) to replacing the section of plumbing line, likely PEX, with a new piece entirely (and you'll need a PEX clamp tool + clamps like this: https://amzn.to/3VxmgDA).
But it could be a failed backflow preventer inside the water pump itself, in which case you could put an inline backflow preventer on the intake side of the pump (again, confirming the size of your plumbing and other fittings to be sure this would fit: https://amzn.to/3I3cUfM).\
Or it could also be a failed pressure switch in the pump itself... it could cycle on because the sensor is telling it the pressure in the lines has dropped, even if it hasn't.
It's a bit of a "Sherlock Holmes" project to figure out which thing it is... and sometimes takes some trial and error to isolate the root cause, but we hope this helps!
Erik
Sunday 14th of July 2024
The vent line may contains just a little water, blocking air flow until slight pressure is built up in the tank. If you use a spout on your water hose, its diameter may be small enough that air escapes around the spout more easily than through the vent. The spout may also cause the water stream to speed up and splash, even pumping air into the tank. If you have problems with water backflowing long before the tank is full, try removing the spout and inserting the wider fill hose directly into the fill hole. This will cause the water stream to be wider and slower, and reduce the tendency of venting air to bypass the normal vent path.