Misreading sensors are a very common problem that almost all RVers deal with while camping. A lot of information is available about how to restore, clean, and fix RV black and gray holding tank sensors, but information is severely lacking when it comes to RV fresh water tank level sensors.
For RV black and gray holding tank sensors, you can find safe, reliable, and effective ways to clean and restore them, but RV freshwater tank sensors can’t be cleaned and restored the same way.
If you’re dealing with misreading or failing RV water tank sensors, this guide will help you understand why your RV fresh water tank sensors are not working, why trying to clean RV fresh water tank sensors is a waste of time, and learn step-by-step instructions about how to replace RV water tank level sensors with confidence.
For help with RV black and gray tank sensors: RV Holding Tank Sensors: How They Work and How to Clean Them
Key Points About RV Fresh Water Tank Sensors
- Most RV fresh water tank sensors function as an electrical circuit where the rising water levels in your holding tank completes the circuit and lights up the corresponding level gauge.
- Misreading RV water tank level sensors are typically caused by hard water and mineral deposits, but on rarer occasions can also be caused by wiring or control problems.
- RV water tank sensors are challenging to restore because of hard-to-clean mineral buildup that RV-safe cleaning products aren’t able to remove effectively.
- If your RV fresh water tank sensors are not working, replacing them is the best option because it provides a long-term, reliable solution, whereas attempting to clean them can not only cause expensive damage to your RV, but is often only a temporary fix that will require recurring maintenance.
Why Do RV Fresh Water Tank Sensors Misread?
RV freshwater holding tank sensors typically fail because of hard water or mineral deposits such as calcium and magnesium. Less frequently, these RV tank sensors can also misread because of wiring or control problems.
Mineral Deposits
The most common cause of misreading RV fresh water tank sensors not reading correctly is mineral buildup. When non-cleanable mineral, calcium, or hard water deposits cover the RV water tank sensors, it prevents them from functioning properly.
This problem can be compounded by campsite water that is typically not managed as well as city water sources. Additionally, water from wells and aquifers have increased chances of causing mineral deposits, particularly if they are in close proximity to limestone, chalk, or gypsum.
Wiring Problems
RV water level tank sensors can also malfunction if there is a wiring problem. For example, there might be a broken wire from a ring terminal, wire insulation could rub through causing the wire to ground, or the wire might be pinched.
In these instances, the damaged wire will need to be repaired or replaced to fix the problem.
Control Problems
This is the least likely cause of RV fresh water tank sensor problems, but poor connection at the Molex connector to the circuit board, failed resistors, etc. can also prevent sensors from working.
If the control board has suffered damage, it will need to be fully replaced in order for your sensors to read correctly.
Find out more about why RV tank sensors misread: Why Are My RV Sensors Not Working? How Do I Fix Them?
Can you Prevent Mineral Buildup in RV Freshwater Tanks?
You can’t completely prevent mineral buildup in your RV fresh water tanks, but you can slow down the process with a few simple techniques.
Be Mindful of Where You Fill Your RV Fresh Water Tanks
While being selective about which water sources you’re using to fill your RV freshwater holding tank can help mitigate the build up of minerals, this technique can be difficult to maintain when specific water options are limited or not available.
However, if you’re trying to be mindful about where you’re filling your RV fresh water tank, hard water test kits are budget-friendly, and may be helpful when choosing where to fill your RV fresh water tanks.
Ensure Proper Filtration & Use Water Softeners in RV Water Tanks
Allowing the water in your RV fresh water tank to evaporate can also increase mineral buildup. To slow this process, you can filter the water and run it through a water softener. While this method can work, it is often not considered the most practical option because the reduction in mineral buildup does not justify the relatively high cost of water softeners.
Additionally, when campers need to fill their RV freshwater tanks, they often forget to run the water through inline filters, or a series of water filters, and feel that the filtration process slows the tank filling process too significantly.
Bottom Line: While there are things you can do to reduce mineral build up in your RV fresh water tanks, the results are often not significant enough for the effort required.
Why Are Mineral Deposits in RV Freshwater Tanks So Difficult to Clean?
When enough mineral deposits build up on the RV fresh water tank sensors, they become insulated from the water and no longer close the circuit, causing the sensors to misread.
Mineral deposits, mainly calcium, lime, and magnesium, are difficult to remove from RV fresh water tanks because they cause hard, stubborn scale to form that bonds to plastic surfaces over time.
Main reasons that mineral deposits are difficult to clean from RV water tank sensors:
- Plastic Bonding: Minerals, specifically calcium, bond tightly to the plastic surfaces in RV fresh water holding tanks, requiring acidic cleaners to remove.
- Lack of Proper Filtration: Campground water quality varies, and unfiltered or hard water can allow mineral particles to enter the system, eventually leading to buildup.
- Irregular RV Fresh Water Tank Shapes: RV freshwater holding tanks come in different shapes, sizes, and configurations, making it difficult to completely flush out minerals and sediment.
- Hidden Buildup: Mineral deposits can accumulate within the RV water pump, faucet aerators, and showerheads, further increasing the buildup of hardened scale deposits.
Mineral deposits can often not be cleaned effectively, and rather than attempting to clean or restore RV water level sensors, sensor replacement should be considered.
Why You Should Avoid Cleaning RV Fresh Water Tank Sensors
As we’ve discovered in this article, mineral buildup is the main cause of RV water tank sensors misreading. Unlike RV black and gray water holding tanks that can be cleaned with bacteria- and enzyme-based RV tank treatments like Unique Restore-It or Dawn dish soap (respectively), mineral buildup requires strong, acidic cleaning solutions to remove.
Some of the common acids that would be used to clean mineral build up are not suitable for RV holding tanks.
Why Acids Are Not Practical for Cleaning RV Fresh Water Tank Sensors
Many effective cleaning products rely on acids to remove stubborn limescale, hard water stains, and rust from surfaces because other neutral cleaners cannot tackle them. While acids seem like a logical solution for the mineral buildup in your RV water tanks, let’s take a closer look at how they are not only impractical, but may actually do more harm than good.
Vinegar, Lemon Juice, or Citric Acid
These acids are often cited as recommendations for cleaning hard water, but they must be undiluted to be effective. This means that depending on the size of the freshwater tank, you would potentially need dozens of gallons for the treatment to be effective.
Hydrogen Peroxide, Baking Soda, Borax, or CLR
Commercial hard water cleaners can be effective at cleaning hard water, but often require scrubbing to clean away the mineral build up.
The problem is that RV fresh water holding tank sensors are often secured in place and made water tight with bushings. When these bushings are removed to access and clean the RV water tank sensors, they typically hold their shape, and therefore make them very difficult to reinstall while remaining water tight.
In addition to being impractical, and potentially dangerous for human consumption, acidic cleaners can be
detrimental to RV holding tanks and components.
How Harsh Cleaners Can Damage RV Fresh Water Tanks & Components
RV water tank sensors, tanks, and other components are typically made of plastic and rubber, which can be damaged by caustic chemicals.
In fact, harsh cleaners can cause the following issues in RV fresh water tanks:
Damage to Rubber Seals & Valves
Harsh acids and chemicals can dry out and destroy the rubber seals and gaskets that are used to make water tight connections at fittings for the water fill connection, sensor gaskets, and the low point drain.
If these acids or chemicals are pumped out of the RV freshwater tank, they may cause damage to the water pump, fittings, and other gaskets in the RV black and gray water tanks. They may also contaminate the freshwater supply plumbing, which may be a safety issue.
Increased Sensor Malfunctions
Acids can damage, dull, or pit the plastic and metal components of RV fresh water tanks, causing sensors to give incorrect readings, or completely fail.
Environmental Hazards
When harsh or acidic cleaners are dumped into campground septic systems, they can kill the microbes necessary for sewage treatment, leading to environmental harm and potential system failure.
Dumping acids and chemicals directly on the ground from the low point in RV freshwater tanks is illegal, and may cause significant environmental damage.
Creates Toxic Gas
Mixing acid-based cleaners (vinegar or certain toilet bowl cleaners) with bleach can create toxic chlorine gas, which can be dangerous in the confined living space of an RV.
Learn More: Choosing the Right Products or Methods for Cleaning RV Tank Sensors
Important Note: There aren't any professional RV fresh water tank sensor cleaners on the market because of how difficult it is to clean them without causing damage to your RV, or health risks to you. Experienced RV techs (ours included) always encourage campers to replace rather than fix RV fresh water tank sensors.
Why Replacing RV Fresh Water Tank Sensors is the Best Approach
If your RV freshwater holding tank sensors are misreading, the recommended solution is to replace them.
Replace RV water tank sensors rather than cleaning them for the following reasons:
- Cost Effective: RV water tank level sensor replacement is the most cost-effective option, because RV tank sensors are relatively affordable.
- Long-Term Results: Attempting to clean sensors with mineral buildup is rarely effective, and even if you are successful, you’ll need to repeat the process frequently. Replacing the RV water tank sensors gives the most reliable and long term results.
- Prevents Damage: Attempting to clean stubborn mineral buildup is very difficult, especially without the use of acids or other harsh chemicals that can damage your RV holding tank and its components.
- Maintenance Opportunity: Replacing the RV water tank sensors also gives you the opportunity to check all of the wiring connections, and tighten them if necessary. We also recommend checking the RV water pump filter for build up on the screen, and replacing it if necessary (the freshwater pump is typically located close to the RV fresh water tank).
How to Replace RV Fresh Water Tank Sensors: Step-by-Step Instructions
Replacing RV freshwater tank sensors involves locating the sensors on the tank, disconnecting the wiring, removing old probes, and installing new ones. For most, this means replacing "nub" or "Horst" style sensors, which can be done by installing new probes at the ground, 1/3, 2/3, and top positions, while ensuring a secure, leak-proof seal.
Recommended Tools: Gloves, adjustable wrench, camera, nut driver, and replacement RV tank sensors.
Important Note: As with any RV maintenance project, if you don’t feel 100% confident in your ability to complete the task on your own, we highly recommend hiring a certified RV tech to complete the project for you. If you choose to replace your RV tank sensors on your own via our instructions, please understand that you do so at your own risk.
Steps to Replace RV Fresh Water Tank Sensors:
- Step 1 — Empty RV Freshwater Tank.
- Step 2 — Locate & Access RV Freshwater Tank: Often the most difficult part of the process, the RV fresh water tank is typically located behind panels, under beds, or sandwiched between subfloors and the frame housings.
- Step 3 — Identify Old RV Water Tank Sensors: Locate the RV water tank sensors, which are usually small metal studs with wires attached and held in place with nuts (typically 3/8“).
- Step 4 — Take Photo or Create RV Water Tank Sensor Wiring Diagram: Use your camera to take a photo of the RV tank sensors, and their wiring configuration, to make reassembly easier. You can also opt to create your own RV fresh water tank sensor wiring diagram.
- Step 5 — Disconnect RV Tank Sensor Wiring Terminals: Remove the nut completely, and then remove ring terminals to get the wiring out of the way. Loosen the second nut to relieve the mechanical pressure that expands the rubber bushing to make a water tight seal.
- Step 6 — Remove Old RV Water Tank Sensors: Remove the old, broken, or corroded sensor probes. If the RV tank sensors are difficult to remove, position the adjustable wrench between the nut and the washer. This gives you leverage to press against the outside of the holding tank and pop it free. Alternatively, you can grip the threaded stud with pliers and pull firmly away from the tank.
- Step 7 — Position New RV Water Tank Sensors: Remove a nut on one side of the new sensor, and pop it into the hole where the old sensor used to be (button head inside, threaded side outside).
- Step 8 — Seal the RV Water Tank Sensors: Tighten the backing nut until the bushing on the inside of the tank begins to expand. As it expands, it will make it so that the RV water tank sensor cannot be dislodged from the hole while creating a water-tight seal.
- Step 9 — Reconnect RV Water Tank Sensor Wiring: Reference your picture or diagram of the wiring setup, reattach the appropriate wires, and replace the tightening nut back in place to push the ring terminals together. Caution: If the sensors are not wired correctly, they will misread.
- Step 10 — Secure RV Freshwater Sensor Connections: Tighten RV tank sensors and wiring down to ensure nothing comes dislodged when the RV is back on the road.
- Step 11 — Check for RV Tank Sensor Functionality & Leaks: Fill the RV freshwater tank to confirm the sensors are reading accurately, and there aren’t any leaks around the newly-installed RV tank sensors.
Alternative RV Freshwater Tank Sensors: More Reliable Options
If the constant cycle of misreading RV water tank sensors followed by replacement has you feeling down or frustrated, don’t worry, there’s an alternative — actually, there are at least three.
If you want to avoid RV sensors that rely on traditional probes, try these alternatives:
-
Garnet
SeeLevel RV Tank Sensors: Available for aftermarket installation for over 30 years, these
externally-mounted RV tanks sensors are the most reliable, go-to option.
- Briidea RV Sensors: Rely on a non-contact water level detection method that uses sonar technology.
- American Technology Components Adhesive External Sensors: Utilize external probes that easily stick to the outside of the RV water tank.
These alternative RV fresh water tank sensors are especially effective in RV freshwater tanks because there is little to no solid waste or debris in fresh water tanks. They’re also easier to install, and less likely to misread as a result of mineral buildup.
In fact, they’re so reliable that the SeeLevel holding tank sensors are now being installed by manufacturers on new RVs, typically for larger, high-end Class A, 5th Wheels, in addition to high-end Class B’s, and Travel Trailers.
Important Note: No RV holding tank sensors are perfect, and even alternative RV tank sensors can still be affected by damaged components or wiring issues.
Replace, Don’t Restore: RV Fresh Water Tank Sensors the Smart Way
When it comes to misreading RV water tank level sensors, the right move is to replace them rather than attempt to clean or restore them. Hard water and mineral buildup are very difficult to remove, especially because the harsh cleaners needed can do real damage to your RV holding tanks and components.
Not only are RV water tank sensors fairly inexpensive, but opting to replace them ensures better long-term results while giving you, or a certified RV tech, the opportunity to do routine maintenance checks on your RV wiring and control panel, too!
Still struggling with your RV water tank sensors? Don’t be a stubborn RVer, reach out to the incredible Customer Support Team at Unique Camping + Marine and they’ll help you find a solution today.
