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How Do I Unclog RV Holding Tanks?

You can hydro-jet clogged RV holding tanks using an attachment for your pressure washer that's designed to clean black- and gray-water tanks.
RV holding tanks can clog when solidified waste, mold and struvite accumulate inside the tanks and drain lines. When this happens you may notice:
- persistent odors inside the vehicle,
- holding tank sensors that fail to operate reliably,
- lack of flow when attempting to empty a holding tank, and
- several clogged plumbing fixtures such as a toilet, shower or sink.
When chemical treatments and low-pressure garden hose sprayers fail to solve these problems, you can power wash your tanks using an RV tank cleaning attachment powered by your pressure washer.
An electric pressure washer rated 1.2 GPM and compatible tank cleaning attachment are recommended for safer and more thorough hydro-jetting of RV holding tanks, sensors and drain lines.
Hydro-Jetter for RV Tanks
The Clog Hog RV tank cleaner is a hydro-jetting attachment for your pressure washer with these features required to clean holding tanks:
- a compact nozzle-end that's specially designed to clean the inside surfaces of RV tanks,
- a flexible, steel-braided jetter hose to more easily push and twist through RV drain lines,
- a hands-free control valve that frees both of your hands to work at the RV drain opening, and
- a patented powered inline filter that keeps the nozzle jets spraying with maximum force.
Unlike conventional sewer jetters, the Clog Hog RV tank cleaner has a nozzle with four high-angle jets that provide superior cleaning coverage to more thoroughly clean the inside surfaces of tanks.
Note: if you're unsure about the following steps you can hire an RV tank hydro-jetting service and watch as they clean the tanks to determine if you'll be comfortable doing the job yourself the next time.
To Clean Your RV Holding Tanks
It's usually easiest to insert the RV tank cleaner into the exterior bottom drain opening and pass the nozzle through an open dump valve. Depending on the vehicle layout, you might also insert the tank cleaner through a roof vent or an inside drain opening.
- Using a 1‑1/2" hole saw that attaches to your drill, you can cut a top access port in a clear RV sewer extender fitting, sanding smooth any sharp edges from the cut. The access port minimizes spillage when you hydro-jet the tank, and allows you to inspect the dirty residue as it flushes out.
- Put on fluid-resistant work gloves and eye protection.
- Before hydro-jetting the tank, use your external twist-on waste valve, hydro-flush elbow and garden-hose water meter to nearly fill and flush the tank so that you remove any loose debris.
- Connect the access port to the RV drain line, open the dump valve, and before you turn on the pressure washer guide the tank cleaner nozzle at least two feet into the drain. Then turn on the pressure washer and open the hydro-jetter hands-free control valve to pressurize the nozzle.
- Maintain the flow of pressurized water as you allow the nozzle to pull itself into the drain. You can loop and rotate some of the hose in your other hand to help twist through any drain elbows, and to move the nozzle into different corners of the tank. Important: do not insert the tank cleaner so far into the tank that it could repeatedly loop inside and tie up.
- Continue to move forward until you feel resistance as you reach the end of the tank, pull back, push in as you twist the line with two hands to move into another corner of tank, and repeat until no more dirty residue flushes out. This process can take up to about 25 minutes per tank, depending on the amount of residue to be scrubbed out.
- Turn off the hydro-jetter control valve and pull out the tank cleaner. Use care to stop the flow of pressurized water before the nozzle reaches the drain opening.
- Using your external twist-on waste valve, hydro-flush elbow and garden-hose water meter, nearly fill and flush the tank to remove any remaining residue, then repeat. If you have adequately hydro-jetted the tank, water from the second flush should be almost clear of visible debris.
- Repeat with other tanks as needed.
You can visit the Clog Hog RV tank cleaner product page for more information, including a list of compatible pressure washers.
If you have questions or comments please contact us.