Waste Tanks

The onboard waste tanks are commonly referred to as either the black tank or gray tank.

Black tank. The black tank holds the waste from the commode. Most larger RVs have one black tank, although some rigs that have two bathrooms may have two black tanks. The tanks might have separate drain valves or might be plumbed together - it will just require some inspection to figure it out.

Gray tank. Almost all large rigs have at least two gray tanks. One is usually for bathroom gray water - washer, shower and sink water - and the other gray tank is for the kitchen galley. It’s called gray water because, while it is still dirty water, it doesn’t contain any of the nasty solid waste.

One of the most unpleasant tasks to perform is emptying the waste tanks. We’ve met people on the road who are so paranoid or disgusted with the thought of waste tank maintenance that they literally never use their on-board plumbing. The waste tank system is designed and built to be easily used, and once you understand the system it’s not quite as intimidating.

Waste tanks have a capacity of between 30 and 45 gallons each. There are tank level gauges that are supposed to show how full the tanks are. Be forewarned - they rarely work. You learn that the commode makes a different sound as it gets close to full, and water will back up in the shower or kitchen sink when the tanks are full.

We try to travel with the waste tanks fairly empty. By having empty tanks, we know we have good tank capacity for the campground we’re arriving at in case we don’t have sewer hookup.

Your rig will have some method of storing the sewer hose underneath the rig.

Keep a box of disposable rubber surgical gloves to provide personal protection when handling the sewer hose and connections.

gray tanks

“Gray water” is the term used for non-solid waste water. It’s the water that goes down the drain of your shower, bathroom sink, and kitchen sink.

Your rig probably has two gray water tanks - one for the bathroom and one for the kitchen. Generally, the shower, bathroom sink, and washer will drain into the tank labeled “Gray Tank”, and the kitchen will drain into the “Galley Tank”. The drain system sometimes requires investigation to find out where additional bathrooms drain.

The pull handles for the gray tanks are usually in the convenience center, however in some older fifth wheels the galley tank pull handle is in the driver’s side wheel well.

The gray tanks generally don’t get clogged up because everything in the tank is mostly water. You can keep you galley tank cleaner by having a strainer in the bottom of the kitchen sink so that most food particles are trapped and can be thrown away instead of going down the drain. In the bathroom, hair is the usual culprit for clogged or slow drains.

If you’re parked in a site for a longer time, you can leave the gray tank valves open so the water is constantly draining to the sewer instead of filling the RV tanks.

BLACK TANK

dumping tanks

Never leave the black tank valve open.

The black tank holds the human waste from the commode. As already stated, the key to a healthy black tank is lots of water. Toilet paper and solids break down and dissolve with lots of water.

Never leave the black tank valve open. There is a condition called the “poop pyramid”, which is exactly what it says, that is caused by not having enough water to dissolve the solids. If a poop pyramid develops and then dries out or clogs the tank drain, it can be very difficult to break down and one of the most unpleasant problems to solve in an RV. I’ll say it again: never leave the black tank valve open.

Develop a habit to hold the water flush down between 5 and 10 seconds after using the commode. You just can’t use too much water when flushing.

The subject of toilet paper seems controversial, but we’ve found that any toilet paper safe for septic systems is also safe for an RV system. If you’re really interested, you can do the water breakdown test - get a glass of water and put a single sheet of your favorite toilet paper in the water and see how much time it takes to break down. Then you can compare different brands. I’ve never been interested enough to do this.

For the fourth time, never leave the black tank valve open, no matter how long you are in a site.

The process of dumping the tanks is pretty simple:

• Get the tanks as full as possible, even if you have to add additional water before dumping. The extra water will create more pressure when the tank is dumped, and will carry any solids with it.

• Put on protective surgical gloves.

• Hook up the sewer hose between the sewer and your rig, using the proper fittings so they make a good connection.

• Open the black tank valve and let it drain completely. Then close the black tank valve.

• Open the two gray tank valves and let them drain completely.

• Close the tank valves.

• Disconnect the sewer hose from the rig first and allow the water in the hose to drain into the sewer. If a non-drinking water hose is available, wash out the sewer hose, then disconnect the hose at the sewer end and store.

• Replace the cap on the hose storage and drain line.

Parked at a site. When parked at a site and sewer hookup is available, you can take a little more time to flush the tanks so there is a slight modification to the process:

Open the black tank valve and let it drain, but wait to drain the gray tanks.

The black tank is equipped with a flush system that operates from the convenience center by hooking up a hose to the Tank Flush connection. It operates a sprayer inside the tank that helps wash the sidewalls. I hook up the tank flush, close the drain valve, and start the water. I always set the timer on my phone for 8 minutes. Distractions happen. If you forget about the water running, you will overflow the black tank and it will be a huge mess. And believe me, distractions happen. When the timer goes off, I open the black tank valve and let it drain, then repeat the process. I’ll usually do that three times.

After you’re done flushing the black tank, open the gray tank valves and let the gray water flush out the hose. Then add the tank maintenance mixture of Pine Sol and Calgon.

At a Dump Station. When you have to use a dump station, get in and get out as soon as you can. Waiting in line for the dump station is already a delay in traveling. It’s even more frustrating waiting on someone who thinks their sewer system has to be crystal clear and sanitized at a dump station.

If you’re waiting in line, make sure you’ve got your gloves handy and you’re ready to go when it’s your turn.

Use the process above for dumping.

Don’t wash the black tank with the internal flush system when people are waiting behind you. The tank doesn’t have to be washed after every dump.

After you’ve closed the valves and you’re ready to disconnect the sewer hose, disconnect from the rig first. Use the non-potable water hose (all dump stations should have them) to wash your hose out while its still connected to the sewer. Then disconnect your hose from the sewer and store it. That is the cleanest and quickest way of accomplishing the task.

Replace your caps and move forward to get out of the way. You can dump your trash or add your cleaning mixture when you’re out of the way and not holding up the line.

accessories

There’s a few things that come in handy to help in the process of maintaining the waste tanks:

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