The unfortunate reality is that RV holding tank sensors get clogged or gunked up if you don’t maintain your holding tanks properly. This causes the sensors to read inaccurately, which is why many experienced RVers create a timeline for emptying their tanks rather than relying on their tank sensor readings.
The good news is that there are several methods for cleaning RV holding tank sensors if yours no longer reads accurately. But first, let’s talk about why these sensors get clogged.
Why Do RV Holding Tank Sensors Get Clogged?
To put it bluntly, tank sensors get clogged because your “stuff” impairs their ability to get an accurate reading. In your waste water holding tank (WWHT), body waste and toilet paper sometimes become caked on the sensors. In the gray water holding tank (GWHT), layers of grease and oil can build up on the sensors.
You’ll generally notice that your sensors are reading inaccurately if you’ve been using your RV for a day or two and their level readings haven’t changed. Or, they could still register full tanks when you visit the dump station and are certain you’ve emptied your holding tanks.
If your sensors are reading inaccurately or aren’t reading at all, there are two general causes:
- The sensors are caked or layered with “stuff”
- The sensors are broken
Let’s identify how to prevent that build-up in the first place, then how to clean it, and lastly, how to determine if your sensors are malfunctioning.
How to Prevent Blocked RV Holding Tank Sensors
Here are some techniques for keeping your sensors clean so they continue delivering accurate readings.
- Only use RV toilet paper. It breaks down more quickly and completely than household toilet paper. Avoid two-ply at all costs. Feminine hygiene and birth control products should go in the trash and never down the toilet.
- Regularly use tank chemicals. Add them to your gray and black tanks before each use to keep oils and solids digested and suspended.
- Avoid putting toilet paper down the toilet. Get a small trash can to dispose of TP to eliminate the potential for it to clog your tank sensors.
- Use your black tank flush, if so equipped. Finish each trip (or each visit to the dump station) with a holding tank cleanse to remove any remaining tank waste.
- Avoid putting cooking oils and grease down the drain. Empty cooking oils and grease into disposable containers and trash them instead of putting them into your gray water holding tank (GWHT). Solid food waste should be scraped into the trash bin and never put down your RV sink.
How to Clean RV Holding Tank Sensors
If you suspect your holding tank sensors to be clogged, here are a few methods you can use to clean them:
Method #1: Tank Chemicals
Using chemicals is the easiest of these five methods, so start here. The are multiple types of chemical-based tank cleaners,, but we’re big fans of drop-in tablets. Follow the manufacturer’s instructions for how much water to fill your tank with before dropping the recommended number of tablets down your RV’s toilet.
You may need to fill your WWHT completely with water before dropping in tablets and waiting the recommended period. After they’ve done their job breaking down waste, empty your tanks and check that your sensors register empty. You’ll then need to fill your tank again to check that the sensors register their ascribed levels accordingly.
Method #2: Dishwasher Detergent
Applicable to both GWHTs and WWHTs, using dishwasher detergent is most effective if employed before you commence your next RV trip. To employ it, empty your holding tanks completely and then fill them with a cup of dishwater detergent and enough water to fill them halfway.
This method requires dishwashing detergent that’s designed for automatic dishwashers, but it’s effective for two reasons.
- These detergents don’t foam as much as others.
- Dishwashing detergents contain softening agents that are very effective at breaking down greases and oils.
With each tank filled at least halfway and a cup of dishwasher detergent in each, your next step is simple: just drive. Your RV’s movement serves as agitation to break down greases, oils, and solid waste and clean your tank sensors.
This method is most effective when you’re heading to a campground with full hookups. When you arrive, connect your sewer hose and empty your tanks as normal. Use this method in conjunction with your black tank flush and/or a tank cleaning wand, as expanded upon below.
Technician Tip: Some dishwasher detergents contain bleach or alkali detergents. If you also use enzyme-based tank chemicals, these detergents may kill the microbes and prevent them from working. If using the blue formaldehyde tank chemical, the combination of chemicals may generate harmful fumes. Always read the labels and rinse thoroughly after treatments.
Method #3: Black Tank Flush
Your black tank flush can prevent clogs and help clean your tank sensors when clogged. It’s best to use this method every time you empty your holding tanks for maximum effectiveness (and to reduce the amount of time it needs to run).
Once flushing, the water will first run dark and chunky. Then, it becomes murky. Finally, it will run clear, indicating the cycle is complete. Add a clear fitting between the termination outlet and the dump hose to accurately assess the condition of the tank water. By doing this every time, the tank is kept extremely clean, and solids will never have the opportunity to accumulate and create issues.
Of course, this method requires that your RV is equipped with a black tank flush, which isn’t true for all RVs. If your motorhome or towable RV doesn’t have one, explore the next method for an alternative.
Method #4: Tank Cleaning Wand
A tank cleaning wand is the best alternative to a black tank flush if your RV isn’t equipped with one. But they work a little differently than the process for using a black tank flush.
This RV accessory connects to a standard garden hose – not the same potable water hose you use to fill your freshwater tank or connect your RV to city water. Why? Because you don’t want to risk contaminating your potable drinking water hose.
Once connected to a garden hose, the tank cleaning wand inserts into your WWHT via your RV’s toilet. Ensure your sewer hose is connected to a drain outlet and your WWHT termination valve is open before proceeding.
Then, turn on the water source and use the wand to clean waste remnants from your tank. This means you’ll need to run a garden hose from a water source, inside your RV, and into your WWHT via the cleaning wand.
And yes, there’s a risk of running water into your RV, which leads to a fun opportunity for a story of personal mishap:
My first RV was a 1987 Tioga Class C. It didn’t have a black tank flush, and it hadn’t exactly been well cared for when we bought it. Staying at an RV resort in Palm Springs for a family New Year’s reunion, we decided to clean the holding tanks.
We ran the sewer hose to the campsite hookup and connected a garden hose to city water. We then threaded the garden hose through the emergency exit, into the bathroom, and down the toilet. Then, we turned on the water source to fill the tank with fresh water in order to flush it.
And…somebody lost concentration or simply got distracted. We overfilled the WWHT, overflowing water into the RV through the toilet. Fortunately, we had already emptied the tank once, and the consequences were mainly water damage.
I share this experience to nurture the point that there’s a better way. If your RV doesn’t have a black tank flush, it’s worth the investment in having a safe, effective way to clean your holding tanks and clear the sensors.
Method #5: Power Cleaning
If the above methods have proved ineffective, there’s one more method worth trying before you explore the possibility of broken tank sensors. Professional tank cleaning services will come to your location to provide what some call an “RV colonoscopy.”
This service generally requires a location with full RV hookups. The technician utilizes a specially designed pressure washer that cleans your tank’s interior walls and removes residue from your sensors.
Method #6: Replace the Sensors
If all methods fail to restore the expected sensor operation, Camping World’s crew of certified RV technicians can provide a tank sensor evaluation. If deemed necessary, they can also replace faulty tank sensors.
The good news is that there’s much you can do to avoid clogged RV holding tank sensors. But if yours are clogged, we hope these methods provide plenty of options for you to get them back to full service again.
Do you have questions about cleaning RV holding tank sensors? Let us know in the comments below.