In part 1 of this article, I discussed ways to alleviate the problem of incorrect level readings for the holding tanks. This week, I will talk about potential methods of clearing holding tank blockages.
You may experience full or partial clogging of the waste holding tank. Symptoms of this will vary, depending on the location and nature of the clog. Sometimes the tank will only partially drain, or not drain at all, other times the toilet will not flush, or the tank will seem to not hold as much waste as before.
If the holding tank will not fully or properly drain, you can try inserting a toilet snake from the tank termination valve end of the plumbing. Construct a tool by purchasing a straight sewer adaptor such as the one shown at left and drilling a hole in the circumference just large enough for a toilet snake. Insert this modified adapter between the RV drain connection and drain hose and make sure the hose is connected to a sewer. Open the tank termination valve until there is nothing coming out. Leave the valve open and feed the snake into the hole in the adapter and up as far as you can into the tank. Be aware that if the blockage clears, waste will flow and may come out the hole in the adapter, so be sure to wear protective equipment and have a catch basin ready. If there is a blockage between the holding tank and the termination valve, the snake should clear it.
Similarly, if there is a blockage between the toilet and holding tank, you can insert the snake from the toilet end. Turn off the fresh water supply, open the toilet gate valve by holding the flush lever open, and insert the snake into the toilet drain. If the snake doesn’t work, and the toilet drain goes straight into the tank without any bends in the pipe, you can also try a wooden stick, metal bar, thick wire, or the like to try to clear the blockage.
If there is a blockage elsewhere that can’t be cleared using the above methods, the first thing I recommend is a toilet flushing wand as I described in last weeks’ article. Toilet flushing wands can be purchased at most stores that sell RV accessories. Most wands consist of PVC tube that threads onto a garden hose on one end and has small water jets on the other. Some also have flex tubing at the jet end for use with toilet drain systems that have bends between the toilet and holding tank. If you’re lucky, a good strong tank flushing will clear your tank blockage.
You can also try a blow bag or drain bladder like the one shown below. I recommend using hot water with these if possible. Note that a blow bag will be much more effective than a snake if the clog is grease-based, since the snake will simply pass through the clog. When using a blow bag, be sure to open the drain valve, and use the modified adapter described above if going from the termination valve end.
If none of these methods work, have the blockage cleared by an RV repair facility. I have had to clear stubborn clogs from RV systems where I have had to remove significant portions of the plumbing in order to get to the blockage.
Note that these tips refer to organic blockages. If the clog is caused by inorganic materials, extraction often requires professional help.
About the Author:
Steve Froese, an avid RV owner, traveler, and Coach-Net member since 2013, is the principal of “A Word to the Wise Technical Communications”, a published RV author, certified RV technician, and licensed Professional Engineer. He frequently collaborates with the “RV Doctor”, Gary Bunzer, and has worked with the RVIA/RVDA as a technical and training writer and consultant. Professionally, he works as a quality engineer and musician. Watch for more of Steve’s work in upcoming Coach-Net publications.
Whenever possible, refrain from dumping your holding tanks until the black water tank is at least 2/3 full. This will allow for the greatest chance of a full drain due to the large vortex created by such a large volume of liquid. Be sure to dump the black water first, then the gray, which will help rinse the drain hose. If you stay connected to the park sewer connection during camping, do not leave the black tank valve open. Doing so will allow the liquid waste to drain, while the solid waste may attach itself to the bottom of the tank instead of going down the drain. If left long enough, the waste will solidify and may not loosen and refloat when it is eventually exposed to liquid again. Sediment waste, although not desirable, often does not cause a problem in the holding tank unless it is allowed to accumulate further, possibly leading to clogging or level indicator errors. In any case, it is best to avoid it.
If you suspect your tank level gauges are not reading accurately, there are a few simple tricks you can try. The first is simply to flush the tank several times. If your coach is equipped with a built-in flushing fixture, open the tank drain valve and run water through the tank flush fitting for several minutes. If you don’t have such a fitting, purchase an RV holding tank flushing wand and use it to clean the tank. Allow the water to run for several minutes. Once either of these operations is complete, check the level readings to see whether the tank level shows as empty. It is of paramount importance that the tank drain valve be left open during these procedures!