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RV University - RV Holding Tank Tips 101
by RV Education 101, an RV industry trusted resource.

What is a Grey Water Tank and a Black Water Tank?

Today we're going to talk about RV holding tanks. Your RV has what is referred to as a grey water holding tank and a black water holding tank. The grey 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.

How Do I Connect my RV to the Sewer?

RV 101 Tip - When you work with waste evacuation and RV holding tanks it is a good idea to wear gloves. There are disposable gloves designed just for this. Check with your local RV camping supply store.

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. They're 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 connect 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.

Now It's Time to Prepare the Black Tank

The first step is to add enough water to the toilet 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 treatment, 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

RV 101 Tip - Some holding tank treatments also contain valve lubricants to keep the valves operating properly and extend the valve seals life.

When should I Empty my Travel Trailer or Motorhome Sewage Tanks?

One golden rule for RV holding tanks is to never empty 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. There is a monitor panel located on the inside of the RV to check the status of the holding tanks.

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 empty the black tank first, followed by the grey tank. The grey water tank should also be at least two thirds full. Emptying the grey water tank last will help to flush out the sewer hose. Every time you empty the black tank you need to treat it with holding tank treatment to assist in controlling odors and to break down solids.

RV 101 Tip - When you're at the campground for an extended period of time you can leave the grey 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 aren't full you can finish filling them with water and then empty them.

Never use your drinking water hose for holding tank maintenance or cleaning purposes. RV drinking hoses are normally white or blue. Take a different color hose (grey, black or green) for other uses so you can distinguish the difference.

After you empty the tanks you need to thoroughly flush the tanks out. Some RVs have a built in system for flushing the tanks. 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 grey tank with a wand.

If a travel trailer or motorhome does not have a built-in flush system, 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.

You should always use toilet paper designed for use in RVs. This toilet paper breaks down and dissolves in the holding tank treatments 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. Read more about RV Holding Tank Sensors & False Tank Level Readings HERE. 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.

Eventually, grease and residue builds up in the grey water tank and causes a foul odor, not to mention how it affects the tank and valve assembly. Periodically treat the grey water tank with environmentally safe holding tank treatments to avoid odors from the tank. When the tank is empty you can also add some dish washing liquid down the sink drains to help break-down grease and residue build-up.

Can I dump my black water tank if I do not have a sewer hook-up at my campsite or when I am traveling?

RV 101 Tip- Never let the grey or black water drain on the ground.

If your campsite does not have a sewer hook-up to drain your black water tank, ask at the campground office where their sewer dump station is located. You need to take your RV to the dump station to empty your black and grey tanks when needed. If you are traveling and you need to empty your grey or black water tank look for a dump station along the way. Some campgrounds offer this service for a fee (make sure you contact the office before going to the designated dump station). Some truck stops and fuel stations offer dump stations too.

RV 101 Tip - Here are five easy tips to keep in mind:

1) Use plenty of water in the black water holding tank.

2) Every time you empty the black water holding tank you need to treat it with a holding tank treatment to assist in controlling odors and to help breakdown solids. Always use environmentally safe holding tank treatments. Enzyme based chemicals use the good bacteria to digest waste and control odors.

3) Use only the amount of holding tank chemicals recommended for the size holding tank you have.

4) Practice good house keeping every time you use a dump station. Imagine if you are the person that has to clean up behind everybody else.

5) Never empty your holding tanks anywhere except in authorized dump stations and campground sewer systems.

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 at www.rveducation101.com cover information on RV holding tanks, the water system, LP gas system, electrical system and more.

Happy Camping,

Mark J. Polk

© Mark J. Polk Founder of RV Education 101

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