Quick answer: to dump RV tanks, put on disposable gloves, connect a sewer hose securely to the RV’s outlet and to the dump station inlet (or campsite sewer connection), open the black tank valve first and let it drain completely, close it, then open the gray tank valve so the soapy gray water rinses the hose. Close the gray valve, rinse the black tank if your RV has a flush system, drain the hose, disconnect, cap everything and rinse the area with the non-potable rinse hose. Dump when tanks are roughly two-thirds to three-quarters full so there is enough liquid to carry solids out, and only ever at an approved dump station or sewer connection.
Emptying the holding tanks is one of the first jobs new RVers worry about, and it is less daunting than it sounds. With the right gear and a simple routine, it takes about 10 to 15 minutes and stays clean. Getting the order and the timing right also prevents most of the clogs, sensor problems and smells that give tanks a bad reputation.
This guide walks through the process step by step. For the bigger picture on choosing and using an RV, see our RV and van camping guide.
Sources: RV manufacturers’ owner’s manuals (holding tank sections); U.S. Environmental Protection Agency (EPA) guidance on RV and boat wastewater; National Park Service (NPS) and USDA Forest Service campground rules on wastewater disposal; state park dump station rules; RV Industry Association (RVIA) consumer resources. Checked October 2026. Always follow your RV’s manual and posted dump station rules first.
Black Tanks, Gray Tanks and Fresh Water
Most RVs with a bathroom have three tanks:
- Fresh water tank: clean water for the sinks, shower and toilet.
- Gray water tank: wastewater from the sinks and shower. Some RVs have two gray tanks, such as one for the kitchen and one for the bathroom.
- Black water tank: wastewater from the toilet.
Each holding tank has its own valve, usually a pull handle labeled on the outside of the RV, and they typically share a single outlet where the sewer hose connects. Many RVs have a tank monitor panel inside, though sensors often read inaccurately once residue builds up on them.
Smaller campervans may use a portable or cassette toilet instead of a black tank, which is emptied by hand at a dump station or approved toilet. Check the toilet manufacturer’s instructions for how and where it can be emptied.
Gear You Need
- Disposable nitrile gloves, and a dedicated pair of reusable work gloves if you like
- A sewer hose with bayonet fittings, long enough to reach the dump inlet (many RVers carry 15 to 20 feet)
- A sewer hose support to give the hose a downhill slope at campsites
- A clear elbow or clear adapter, so you can see when the water runs clear
- A threaded or rubber donut adapter to seal the hose into the dump inlet
- A separate hose for rinsing, clearly marked “not for drinking water,” never your fresh water hose
- A black tank flush hose if your RV has a built-in flush inlet
- A storage bin for sewer gear, kept separate from fresh water gear
Keep sewer gear stored away from anything that touches drinking water, and keep a bottle of hand sanitizer or soap handy.
When to Dump
The usual advice from RV manufacturers is to wait until the black tank is about two-thirds to three-quarters full. Dumping a nearly empty black tank sends liquid out without enough volume and force to carry solids and paper with it, which is how buildup and clogs start.
Gray tanks can be dumped as needed, since they fill faster from showers and dishes. Many RVers save gray water to dump after the black tank so it rinses the hose.
Plan to dump before you leave a campground with a dump station or sewer hookup, rather than driving long distances with full tanks. Full tanks add a lot of weight; water weighs about 8.3 pounds per gallon, so a 40-gallon black tank adds over 300 pounds when full.
Step-by-Step: How to Dump RV Tanks
- Pull up so the RV’s outlet is close to the dump inlet, usually on the driver’s side, and set the parking brake.
- Put on gloves.
- Check that both tank valves are closed. Then remove the cap from the RV’s outlet slowly, over the dump inlet if possible, in case a valve has leaked.
- Attach the sewer hose to the RV outlet, twisting the bayonet fitting until it locks.
- Put the other end firmly into the dump inlet, using an adapter or a weight so it cannot pop out.
- Open the black tank valve. Let it drain completely; you will hear the flow slow and stop.
- Close the black tank valve.
- Rinse the black tank if you have a flush system: connect the non-potable hose to the flush inlet, turn the water on, and watch the clear elbow until the water runs mostly clear. Then turn off the water and let it drain. Follow your manual, and never leave a flush running unattended, since overfilling can push water back into the RV.
- Open the gray tank valve and let it drain. This rinses the hose with soapy water.
- Close the gray valve.
- Drain the hose by lifting it from the RV end toward the inlet.
- Disconnect the hose from the RV first, cap the outlet, then remove the hose from the inlet and rinse it with the non-potable rinse hose.
- Rinse the area around the dump inlet and put the inlet cover back.
- Add water and tank treatment to the black tank as your manual suggests, usually a few gallons through the toilet so the bottom of the tank is covered.
- Remove gloves and wash hands.
Dumping at a Full-Hookup Campsite
At a site with a sewer connection, the process is the same, but you may stay connected for days. A common mistake is leaving the black tank valve open the whole time. Liquids drain away and solids are left behind, building into a stubborn mound that clogs the tank and confuses sensors.
Keep the black valve closed and dump it when it is two-thirds full or before you leave. Some RVers leave the gray valve open at full hookups, but closing it a day before dumping the black tank ensures you have gray water to rinse the hose. Our guide on RV hookups explained covers water, electric and sewer connections.
Where to Find Dump Stations
Dumping wastewater anywhere other than an approved dump station or sewer connection is illegal in most places and harms water and soil. The EPA and land agencies treat RV wastewater as sewage that must go into proper treatment systems.
Common places to dump include:
- Many public and private campgrounds; some allow non-campers for a fee
- Some state park and national park campgrounds
- Some highway rest areas and visitor centers
- Some travel centers and fuel stations that serve RVs
- Some municipal wastewater facilities
Apps and websites that list dump stations can help, but call ahead or check recent reviews, since stations sometimes close for the season or for repairs. Our guide to types of RV campgrounds explains what hookups to expect at different kinds of parks.
If you camp without hookups, track your tank levels so you know how many days you have. Our guide to RV boondocking for beginners covers stretching your tank capacity.
Keeping Holding Tanks Clean Between Dumps
A little routine maintenance keeps tanks emptying smoothly and keeps odors down.
Tank treatments
Most RVers add a black tank treatment after each dump. Treatments generally fall into a few types: enzyme or bacteria-based products that help break down waste and paper, and deodorizing products that control smell. Some campgrounds and states discourage or restrict treatments containing formaldehyde or other harsh chemicals because they can disrupt septic systems at the campground, so check the label and choose products marked as septic-safe where required.
Use plenty of water
Water is the single most helpful thing for a black tank. Keep a few gallons in the bottom of the tank after dumping, and hold the toilet flush pedal a little longer than you might think necessary so solids are carried into the tank and spread out.
Deep cleaning
Every so often, or before storage, many owners do a more thorough rinse: dumping, partially filling the tank with water through the toilet or flush inlet, driving a short distance so the water sloshes around, and dumping again. Tank wands that reach through the toilet are another option for RVs without a built-in flush. Follow your manual so you do not damage sensors or valves.
Gray tank odors
Gray tanks can smell too, often from food scraps and grease. Use sink strainers, wipe greasy pans before washing them and run a gray tank rinse now and then.
Valve care
Valves that are hard to pull or that leak are often due to dried residue or worn seals. Regular rinsing helps, and seals and valves can be replaced if needed.
Dump Station Etiquette
- Pull all the way forward so the next RV can pull in behind you if there are two lanes.
- Have your gear ready before you pull up.
- Use only the non-potable rinse hose for sewer gear; never use the potable water spigot to rinse hoses.
- Do not leave anything behind, including gloves and caps.
- Rinse spills into the inlet, not onto the ground.
- If there is a line, save tasks like sorting gear for after you pull away.
Common Mistakes and How to Avoid Them
- Dumping gray before black. You lose the gray water rinse for the hose. Black first, then gray.
- Leaving the black valve open at hookups. It leads to buildup and clogs.
- Not using enough water. Use plenty of water when flushing, and add water to the tank after dumping.
- Using household toilet paper. Some types break down slowly. Many RVers use quick-dissolving paper labeled for RVs, or test their paper by shaking a few squares in a jar of water.
- Putting the wrong things down the toilet. Wipes, even “flushable” ones, feminine products and grease cause clogs.
- Using the fresh water hose for rinsing. Keep sewer and drinking water gear completely separate.
- Pulling a valve with the cap off and no hose attached. Always check valves before removing the cap.
These are among the classic first-trip problems covered in our guide to RV first trip mistakes.
Cold Weather Notes
Holding tanks and valves can freeze in cold weather. Many RVers keep tanks closed until they need to dump, since slowly draining water can freeze in a hose. Some RVs have heated tank pads or enclosed underbellies. Before storing an RV for winter, dump and rinse the tanks fully; our guide to how to winterize an RV covers the full process.
Frequently Asked Questions
Should you dump the black or gray tank first?
Black first, then gray. The gray tank’s soapy water rinses the sewer hose after the black tank empties.
How often do you need to dump RV tanks?
It depends on tank size and use. Many RVers dump the black tank when it is about two-thirds to three-quarters full, which might be every few days for a couple using the RV full-time.
Can I dump gray water on the ground?
In most places, no. Many land agencies and states prohibit dumping gray water on the ground, and black water must always go into an approved dump station or sewer. Check local rules.
Why does my RV tank sensor always read full?
Residue and paper stuck to the sensors are common causes. Rinsing the tank regularly and using enough water usually helps; follow your RV manual for cleaning methods.
What do I need to dump RV tanks for the first time?
Gloves, a sewer hose with fittings, an inlet adapter, a clear elbow, a non-potable rinse hose and a little patience. Read your manual first.
The Bottom Line
Dumping RV tanks is a routine you will get comfortable with quickly. Wait until the black tank is two-thirds full, gear up with gloves and a good hose, dump black first and gray second, rinse well, and use only approved dump stations. Keep sewer gear separate from drinking water gear, and your tanks will stay trouble-free.
