Today we are going to talk about RV holding tanks. To start off, I wanted to mention something about RV storage tanks that I don’t think a lot of RVs know about. Many of the free dump stations available for RVs are closing due to chemicals that are harmful to septic systems and because RVs are abusing these dump stations. If we want access to these dump stations, it is absolutely essential that we use septic safe chemicals (no formaldehyde), and clean up after ourselves and do not abuse the dump stations.
Your RV has what is known as a gray water holding tank and a black water holding tank. The gray water tank collects dirty water from the kitchen sink, bathroom sink and shower. The black water tank is for the toilet. These tanks terminate at a main outlet used to empty the holding tanks. This is where we connect our sewer hose.
Make sure you have the necessary couplings and connectors. It may be necessary to join two hoses to reach the sewer connection. I recommend that you only use heavy-duty sewer hoses. They are not that expensive and hold up much better. Keep a 10-foot hose and a 20-foot hose on hand. Do not pull or drag the sewer hose across the ground. This will cause it to break or have holes in it.
To connect the sewer hose, make sure both valves are closed and remove the sewer cap. Make the connection by placing the hose adapter over the outlet and turning it clockwise until it clicks into place. Run the other end of the hose to the camp sewer connection. Use the necessary adapters to make the connection and obtain a good seal. It’s a good idea to put some weight on the hose so it doesn’t jump out when you drain the tanks. It may be necessary to use some type of sewer hose bracket to get a good angle from the RV to the campground sewer connection so the tanks drain properly when you empty them. The small valve is for the gray water tank and the large valve is for the black water tank.
A rule of thumb for RV storage tanks is to never dump the holding tank until it is at least two-thirds full. You want the tank to be nearly full so weight and gravity will force the contents of the tank to drain properly. Another rule of thumb is to never leave the black tank valve open at camp and expect the toilet to drain or flush like your home toilet. It will not work.
When tanks are full, or nearly full, always flush the black tank first, followed by the gray tank. The greywater tank must also be at least two-thirds full. Emptying the greywater tank last will help flush the sewer hose.
When you’re out camping for an extended period, you can leave the valve on the gray tank partially open to drain while you use it, but remember to NEVER do this with the black tank. If it’s time to leave camp and your holding tanks aren’t full, you can finish filling them with water and then dump them. Never use the potable water hose for holding tank maintenance or cleaning. RV drinking hoses are typically white. Take a different colored hose for other uses so you can tell the difference.
After emptying the tanks, you must thoroughly rinse the tanks. Some RVs have a built-in system for emptying the tanks. If not, there are other ways to do it. You can use a tank wand designed to clean and rinse the black tank. The only problem is that you don’t know when or if the black tank is really clean and you can’t rinse or clean the gray tank with a wand. I use a product called Flush King. It is a reverse flush valve that connects directly to your sewer outlet and flushes and cleans both holding tanks in one operation. It’s easy to use and has a clear barrel so you know when the tanks are really clean.
Every time you dump the black tank, you should treat it with holding tank chemicals to help control odors and break down solids. You should always use environmentally safe chemicals. Enzyme-based chemicals use the good bacteria to digest waste and control odors. Formaldehyde-based chemicals destroy the bacteria needed to break down waste and can be dangerous to humans and pets.
The first step is to add enough water to completely cover the bottom of the tank. Four or five full toilet bowls should be enough depending on the size of your black tank. Water will go a long way in controlling holding tank odors. You always want the contents of the tank to be covered by water. Next, fill the toilet bowl and add the proper amount of holding tank chemicals, typically four ounces for every forty gallons the tank holds. Download the bathroom. Repeat this procedure each time you empty the black water holding tank. Some holding tank chemicals, such as RV Trine, also contain valve lubricants to keep valves working properly and extend the life of valve seals.
You should always use toilet paper designed for RV use. This toilet paper breaks down and dissolves in the chemicals in the holding tank, preventing potential problems with the holding tank, RV sewer system, and dump station septic system.
False holding tank readings on the monitor panel are due to holding tank probes being covered by toilet paper or other debris. If emptying the tank doesn’t solve the problem, add a little water and a couple of bags of ice cubes to the empty holding tank. Drive or pull the trailer so the ice cubes can scrub down the sides of the tank. Proper holding tank chemicals will also keep holding tank probes clean.
Over time, grease and debris build up in the gray tank and cause a bad odor, not to mention how it affects the tank and valve assembly. Periodically treat the gray tank with environmentally safe holding tank chemicals to prevent tank odors. When the tank is empty, you can also add a little dishwashing liquid down the drains to help break down grease and residue buildup.
Following these simple holding tank tips can prevent problems and give you long-lasting, trouble-free holding tanks. This is a problem we can all do without! All of our RV tour videos cover information on RV holding tanks, the water system, the LP gas system, the electrical system, and more. Check out our new “RV Essentials” DVD to show you what items you’ll want for your RV to make all your RV experiences more enjoyable.
happy Camp,
Mark J. Polk
Copyright 2006 by Mark J. Polk owner of RV Education 101
