Today we're going to talk about RV holding tanks. To start with, I wanted to mention something about RV holding tanks that I don't think a lot of RVers are aware of. Many of the free dump stations available to RVers are closing because of chemicals that are harmful to septic systems and because RVers are abusing these dump stations. If we want to have access to these dump stations it is absolutely essential that we use septic safe chemicals (no formaldehyde), and that we clean up after ourselves and do not abuse dump stations.

Your RV has what is referred to as a gray water holding tank and a black water holding tank. The gray water holding tank collects dirty water from the kitchen sink, bathroom sink and shower. The black water holding tank is for the toilet. These tanks terminate into one main outlet used to empty the holding tanks. This is where we connect our sewer hose.

Make sure you have the required couplings and connectors. It may be necessary to attach two hoses together to reach the sewer connection. I recommend you only use heavy duty sewer hoses. Their not that expensive and they hold up much better. Keep a 10 foot hose and a 20 foot hose available. Do not pull or drag the sewer hose on the ground. This will cause it to tear or get pin holes in it.

To hook up the sewer hose make sure both valves are closed and remove the sewer cap. Make the connection by putting the hose adapter over the outlet and turn it clockwise until it locks securely in place. Take the other end of the hose over to the campground sewer connection. Use the necessary adapters to make the connection and get a good seal. It's a good idea to place some weight over the hose so it doesn't jump back out when you drain the tanks. It may be necessary to use some type of sewer hose support 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.

One golden rule for RV holding tanks is to never dump the black water tank until it is at least two thirds full. You want the tank nearly full so the weight and the gravity will force the contents of the tank to drain properly. Another golden rule is to never leave the black tank valve open at the campground and expect the toilet to drain or flush like the toilet in your home. It won't work.

When the tanks are full, or nearly full always dump the black tank first, followed by the gray tank. The gray water tank should also be at least two thirds full. Dumping the gray water tank last will help to flush the sewer hose out.

When you're at the campground for an extended period of time you can leave the gray tank valve partially open so it drains as you use it, but remember to NEVER do this with the black tank. If it's time to leave the campground and your holding tanks are not full you can finish filling them with water and then dump them. Never use your drinking water hose for holding tank maintenance or cleaning purposes. RV drinking hoses are normally white. Take a different color hose for others uses so you can distinguish the difference.

After you dump the tanks you need to thoroughly flush the tanks out. Some RVs have a built in system for flushing the tanks out. If not there are other ways to do it. You can use a tank wand designed for cleaning and flushing the black tank. The only problem is 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 the Flush King. It's a reverse flush valve that connects directly to your sewer outlet and rinses and cleans both holding tanks in one simple operation. It's easy to use and it has a see through barrel so you know when the tanks are really clean.

Every time you dump the black tank you need to treat it with holding tank chemicals to assist in controlling odors and to 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 that's needed to break down waste and they 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 toilet bowls full should be enough depending on the size of your black tank. Water will assist a great deal with 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, usually four ounces for every forty gallons the tank holds. Flush the toilet. Repeat this procedure every time you empty the black water holding tank. Some holding tank chemicals like RV Trine also contains valve lubricants to keep the valves operating properly and extend the valve seals life.

You should always use toilet paper designed for use in RVs. This toilet paper breaks down and dissolves in the holding tank chemicals preventing potential problems with the holding tank, the RV sewer system and the dump station septic system. False holding tank readings on your monitor panel are caused by the holding tank probes being covered by toilet tissue or other debris. If flushing the tank doesn't solve the problem add some water and a couple bags of ice cubes to the empty holding tank. Drive or pull the trailer so the ice cubes can scrub the sides of the tank. Proper holding tank chemicals will also keep the holding tank probes clean.

Over time grease and residue builds up in the gray tank and it causes a foul odor, not to mention how it is affecting the tank and valve assembly. Periodically treat the gray tank with environmentally safe holding tank chemicals to avoid odors from the tank. When the tank is empty you can also add some dish washing liquid down the drains to help break down grease and residue build up.

Following these simple holding tank tips can prevent problems and provide you with long lasting trouble free holding tanks. This is one problem we can all do without! All of our RV walk-through videos cover information on RV holding tanks, the water system, LP gas system, electrical system and more. Check out our new RV Essential Items DVD to show you what items you will want for your RV to make all of your RV experiences more enjoyable.

Happy Camping,
Mark J. Polk

Copyright 2006 by Mark J. Polk owner of RV Education 101

Mark Polk

Mark Polk is a retired U.S. Army Chief Warrant Officer Three, specializing in wheeled and track vehicle fleet maintenance operations. Polk owns and operates RV Education 101, (based in North Carolina) since 1999, and also has an extensive RV background working in RV service, sales and management. Polk has a degree in Industrial Management Technology with 30 plus years of experience in maintenance includes working as an RV technician, a wheeled vehicle and power generation mechanic, an automotive maintenance technician, Battalion and Brigade level Maintenance Officer, an RV sales manager and also in the RV financing department as the Finance & Insurance manager.