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RV Sewer FAQ
- RV Sewer FAQ
- How do you empty RV tanks?
- Can I leave the RV black tank open?
- Can I leave the RV grey tank open?
- How often do you need to empty RV waste tanks?
- Where do you empty RV tanks boondocking?
- Is it OK to dump grey water on the ground?
- What is the difference between grey water and black water?
- How can you empty RV tanks without moving the RV?
- What do I need to empty RV tanks?
- What kind of toilet paper is safe for RV tanks?
- How does an RV sewer system work?
- What is the best RV toilet paper?
- Where to find RV dump stations?
- What order do you dump RV tanks?
- How to stop your RV black tank from smelling?
- How do you know when the black tank is full?
- How do I flush my black water tank?
- How do you flush your black tank if you don't have a built-in flush system?
- How do I make sure my black tank doesn't clog?
- What is a black water tank?
- What is a grey water tank?
- What is a fresh water tank?
1) Connect your sewer hose to your RV tank outlet and the dump station or campground hookup.
2) Test your sewer hose connection by emptying a small amount of grey water. Close the grey tank valve.
3) Open the black tank and leave it open until all of the waste has flowed into the sewer. Close the black tank.
4) Open the grey tank and let it empty. Close the grey tank.
* Your black tank should be at least 2/3 full before you empty it.
For detailed step by step instructions check out How to Dump RV Waste Tanks: Easy (No Mess) Guide
No! Never leave your RV black tank open. It will become hopelessly clogged! An RV black tank should only be open when it is being emptied or flushed.
Yes, you can. When you are connected to a campsite sewer hookup it’s fine to keep your grey tank open. If you do, it’s a good idea to build a P-trap into your sewer hose connection. Make a U shaped dip in your sewer hose. The lower area will fill with water and separate your grey tank from the campground sewer system. 
RV sewer hose with P-trap
Keep in mind, your grey water is used to rinse the sewer hose after you empty the RV black tank. So you’ll want to close the grey tank and let it fill shortly before dumping the black tank.
Anywhere from 2 or 3 days to 2 weeks. It depends on the size of your tanks and how much you use them.
The best way to find out is to create your own baseline. Use water normally and note how long it takes for your tanks to fill. Then try it again in boondocking (or water conservation) mode. Once you do this a few times, you’ll have a good idea of how often you’ll need to empty your tanks. It’s easiest to do at a campground with hookups so you can simply dump your tanks when they’re full.
While boondocking you can either drive your RV to a dump station or use a portable waste tank (aka Blue Boy) and bring it to the dump station.
No. Despite the fact that grey water is cleaner than black water, dumping it on the ground is not generally allowed. In some states, grey water is actually classified as sewage!
RVs have two waste water holding tanks, black and grey.
The grey tank holds everything that drains from the RV sinks and shower – grey water.
The black tank holds everything that is flushed down the RV toilet – black water.
To empty your holding tanks without moving the RV you can use an RV portable waste tank or a honey wagon service.
RV Portable Waste Tank: A holding tank on wheels designed to allow you to empty your RV waste water into the portable tank for transport to a dump station. Also called sewer totes, these are awesome for anyone planning to boondock or camp in parks without full hookups. Check out How to Choose the Best RV Portable Waste Tank for everything you need to know and our top picks.
Honey Wagon Service: A “honey wagon” truck comes to your campsite, pumps out your RV tanks into their holding tank and carts the waste water away for disposal. It usually costs between $10 and $30.
At minimum, you’ll need a basic sewer hose kit consisting of:
–Sewer hose and fittings for connecting to your RV and the sewer hookup.
-A dedicated hose for rinsing or flushing your black tank. (Not your fresh water hose!)
–Disposable gloves.
–Sewer hose support for setting up at a campground.
-Semi-optional – a bin to store your sewer supplies and keep them separated from everything else.
If you’re planning to RV full time or camp a lot you’ll want to add some upgraded RV sewer fittings and adapters to your kit. They’ll make setting up and emptying your tanks easier. Here’s what we use.
-Extra 10 foot sewer hose section. For use when the sewer hookup is located from your RV outlet.
–Flexible fitting sewer hose seal adapter. For easily connecting to the sewer hookup, even if it is stripped or at an awkward angle.
–Extra gaskets. So that you have them on hand when you need them.
–Clear extension for tank outlet. Extremely helpful when you empty your tanks because you can see what is going on.
For even more sewer fitting upgrades and details check out RV Sewer Hose Kit: Everything You Need & Best Upgrades.
RV toilet paper is the safest option – it’s specifically designed to break down quickly and prevent clogs. That said, some people use septic safe toilet paper without issue. But you’ll have to ask yourself, is it worth it? The last place you want a clog is in your RV black tank! Do not use regular household toilet paper! For more details check out RV Toilet Paper (Necessary or Not?).
The RV sewer system is a gravity based holding tank system that stores liquid waste until it can be drained into a sewer hookup.
RV’s typically have two waste water holding tanks, black and grey. The contents of the toilet flush into the black tank. Sinks and showers drain into the grey tank. Both the black and grey holding tanks have separate outlets that lead to a single sewer outlet outside the RV. Some RVs even have multiple sewer outlets to accommodate extra holding tanks.
When the black and grey tanks are full, they need to be emptied. Here’s how it works:
1) The sewer hose is connected to the RV sewer outlet on one end and a campground or dump station sewer hookup on the other end.
2) Each tank is dumped separately by opening the tank gate valve. Once the valve is opened, gravity forces the contents of the tank to flow through the sewer hose and into the sewer hookup.
The black tank is emptied first, and the grey tank second so that the grey water rinses the sewer hose.
Scott Rapid-Dissolving Toilet Paper for RVs and Boats is hands down our top pick for the best RV toilet paper. It’s not only soft and strong but also designed to disintegrate quickly in the black tank. We’ve been using it for 10 years now and haven’t had a single clog in our tank! Even better, it’s easy to find both online and in sticks and bricks stores like Walmart.
We use RV Trip Wizard to easily find dump stations along our travel routes. Simply open the map and filter by dump station.
Campendium has a free map based dump station locator.
Sanidumps is another good place to find RV dump stations.
First, dump the black water tank.
Second, empty the grey water tank.
The grey water will rinse any leftover black water out of the sewer hose.
Tip: Test your connections by running a small amount of grey water through your sewer hose before dumping your black tank. That way if any connections are loose, you find out with grey water not black!
-Make sure to leave a tiny amount of water in the toilet- this creates a seal that keeps odors in the tank, not your RV.
-Use drop in pods like Walex Porta-Paks. They’re easy to use, help break down waste and toilet paper, and reduce odor.
-Flush your black tank every time you empty it.
-Upgrade your tank vents. The Camco Cyclone is designed to spin with the wind and pull odors out of your tanks.
-Add enough water to cover the bottom of your black tank immediately after you empty it.
-Only empty your black tank if it is more than 2/3 full. If you need to empty it before that, add water until it is 2/3 full!
If you’re lucky you can check your RV tank sensors. Don’t count on it though, they are notoriously finicky.
Listen to the sound when you flush your toilet. You can hear the difference between an empty tank and a full tank!
After you empty your tanks, make sure that your black water tank gate valve is open.
Connect your dedicated black tank hose (not your fresh water hose!) to your tank flush inlet and turn on the water.
Let the water flush the tank until it runs clear. You’ll need a clear elbow adapter or clear extender to see what is going on as you do this.
DO NOT FORGET TO MAKE SURE THE BLACK TANK GATE VALVE IS OPEN. If you don’t open the valve you’ll have nasty black water spewing out of your RV toilet and possibly even out of the vent on your roof!
If you do not have an integrated black tank flush system you can use one of the following add on black tank flush systems.
Rhino Blaster Sewer Tank Rinser – A clear sewer tank rinsing adapter that connects to your RV tank outlet with a bayonet swivel fitting. It allows you to connect a hose to flush your black tank and also to see when it runs clear. IMO, this is the easy type of add-on flush system to use.
Straight tank cleaning wand – For RVs with a black tank directly below the toilet. The wand is inserted through the toilet to rinse the inside of the tank.
Flexible tank cleaning wand – For RVs with a black tank that is offset from the toilet.
-Use RV safe toilet paper that is designed to break down quickly.
-Add extra water every time you flush the toilet.
-Use drop in pods like Walex Porta-Paks to help contents break down quickly and minimize odors.
-Only flush human waste and toilet paper.
-Use a clear extension adapter when you empty your black tank and watch. This lets you catch any clogs the moment they start and before they cause a total blockage! If you notice that it starts to empty more slowly than normal, flush and rinse your tank until it empties normally.
The RV black tank is a waste water holding tank that collects everything that is flushed down the toilet. They are designed to allow you to use your RV toilet both on and off grid. Once the black water tank is full, it needs to be emptied into a dump station or campground sewer hookup. The black water tank can also be emptied into a portable RV waste tank or by a honey wagon truck so that the waste can be transported to a dump station without moving the RV.
The RV grey tank is a waste water holding tank that collects everything drains from the RV sinks and shower. They allow you to use your RV water both on and off grid. Once the grey water tank is full, it needs to be emptied into a dump station or campground sewer hookup. The grey water tank can also be emptied into a portable RV waste tank or by a honey wagon truck so that the waste can be transported to a dump station without moving the RV.
The RV fresh water tank holds clean water in order to provide you with running water while off grid. When using the RV sinks, shower or toilet off grid, the water is pumped from the fresh water tank. The RV fresh water tank should always be filled with potable water. When an RV is connected to a campground water hookup (aka city water) the fresh water tank is bypassed and all incoming water comes directly from the campground water spigot.
Always use a dedicated drinking water safe hose for fresh water. Never use your black water hose to fill your fresh water tank or connect to city water!
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We’ve been full-time RVers since 2012. Over 127,000 miles and 47 states later, we are still towing our home around the United States.
On TowingHome we share what we have learned along the way; what we love (and what we don’t) about the RV lifestyle, tips and tricks, our favorite campgrounds, places and gear.
We hope that it makes your journey a little bit easier.