RV Waste Valves: What You Need To Know

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By Kelly Beasley

RVing is fun and exciting! It's a great way to see new destinations and to create new memories. As fun as it is, part of the 'joys' of RVing is dealing with the good AND the bad.

Sure, camping is a great way to take a family vacation, but it's not always unicorns and rainbows. Sometimes it involves dealing with some gross.

The specific gross we're covering here is your RV holding tanks and the corresponding RV waste valves.

While waste tanks are FAR from delightful, it's best you know a few things about them. One thing to know is every tank has an RV waste valve that keeps the liquid in until you dump.

The most important thing to know is that the RV waste valve assembly on every tank can leak.

If your RV waste dump valve leaks or breaks, it must be addressed (unless you like having sewage on your hands and on the ground every time you dump.)

That said, let's look at what an RV waste gate valve is/looks like and familiarize you with what to do when it goes wrong.

Rhino tank gate valve

What Is An RV Waste Valve?

An RV waste valve simply allows you to dump your holding tanks at an appropriate facility. Let's explain a bit more.

So your recreational vehicle has holding tanks underneath it. Their job is to hold everything that goes down your toilet and drains (typically a kitchen sink, bathroom sink, and shower).

They are called the black tank and the gray tank.

  • Black Tanks: Holds sewage from the toilet
  • Gray Tanks: Holds wastewater that goes down your drains (sink & shower)

These waste tanks have pipes that lead to your dump opening. The dump opening is where RV sewer hoses are attached when emptying your tanks.

In between the tank itself and the outlet pipe where you dump is a waste gate valve (a door). Without this door, what goes into the tank would simply come down the waste pipe.

RV waste valve assembly

Waste Valve Assembly (outlined)

If that were the case, liquid waste would come pouring out once you took off the cap at the end of the pipe (to dump).

Hence, the need for a door in between, to hold the waste water in the appropriate tank until it is time for you to empty the tank(s).

Usually, the valves are opened and closed by a connected long 'arm' with a handle at the end (though some higher-end RVs dump by the push of a button via an electrically operated camper waste valve).

These valves are called 'gate valves' (or an RV slide valve) because they operate much like a gate. When in the closed position, the 'gate' closes the outlet much like a gate closes off a road. When in the open position, the 'gate' slides out of the way and allows for free flow of water (opens the 'road').

What Goes Wrong With RV Sewer Valves?

RV sewer valves can go bad in a couple of ways. They either will leak waste water (not seal the tank closed completely), or they will get stuck and not slide freely.

Your sign that there is a problem is when you remove the sewer cap to dump, and you're greeted by liquid waste (sewage or gray water) that shouldn't be there.

RV holding tank valve handle

Holding Tank Valve Handle & Extension Rod

It COULD be that you didn't fully close a valve, so don't panic just yet.

However, if it happens more than once, you have one of these three issues:

  • Cracks: The RV sewer valve seals are cracked/leaking
  • Debris: Debris can get stuck in the valve 'doorway,' causing waste water to leak through the seals
  • Jam: The RV waste valve is stuck closed (or open, or partially between open and closed)

When it's a debris issue, opening and closing the valve while rinsing water through it (either by flushing it through from toilet or sink, OR by doing a backflush from the sewer pipe) might dislodge the offending bits.

This is an easy fix when it works. If you have a very slow leak, it could be debris. Try this resolution first.

If that doesn't stop the problem, you should replace the leaky RV holding tank valve.

Figure Out Which Valve Is Leaking

To find out which valve is leaking, just follow the below steps. (You likely have two RV waste tank valves. However, you may have three, or you may have one.)

If you only have one, there's no need to test.

If you have two or three, test.

RV sewer valve size comparison

Gray Tank Valve (left) & Black Tank Valve (right)

How To Find Which Valve Is Leaking

  1. Empty your tanks and then close your valves.
  2. It's a good idea to wait until the sewer pipe has thoroughly dried out.
  3. Put a bucket under the opening of your sewer outlet.
  4. Run 5-10 gallons or so of water into your toilet. Wait a few minutes and see if it leaks out of the sewer outlet.
  5. If it's leaking, you have debris in that valve opening, or it's leaking. Drain that water.
  6. Perform the same test with your gray tank.
  7. Whichever one leaks needs a new gate valve. If both leak, both valves need replacing.

How To Replace A Leaky Valve

Thankfully, installing a new gate valve is pretty simple for not much money. Valves come in two sizes.

  • Black tank: 3 inches
  • Gray tank: 1.5 inches

All you need is a wrench and a socket (OR you can take it to a service center).

Here's a short video showing how easy it is to replace your valve:

It's a simple procedure. Take out the bolts holding the RV black tank valve (or gray tank valve) assembly in place.

Remove the assembly and seals. For best results, check for any leftover debris and remove. Clean around the openings in between the pipes.

Insert the new assembly. Tighten the bolts down, and your RV sewage valve is ready for you to leave for your next trip!

These instructions are assuming you have easy access to your RV holding tank valves. Some trailers have heated tanks that are covered with a shroud or underbelly covering which makes accessing the valve assemblies a bit more challenging.

You may first have to undo the shroud or even cut an access panel into the covering to gain access. Not a deal breaker, but does complicate the process a bit more.

RV Sewer Valve Frequently Asked Questions:

How Do You Unstick A Black Valve?

You can try a few things to unstick your black tank valve. However, in the end, your best course of action is likely to replace the whole valve assembly.

First, pour some dawn dishwashing detergent into the offending tank. Make sure you put water into the tank first, of course. Let it soak, then try opening the waste valve again.

Next, try tapping on the valve lightly with a hammer, and this might create enough disturbance to get the closed waste valve to open.

Try tapping on the 'door' itself to get it moving. Be aware that if you use the hammer method, the whole thing could break, and you'll need to replace the gate valve after all. (Tap gently! Don't smack it like it's a nail.)

No big deal though, it's a pretty cheap and easy fix that you probably needed to do regardless.

Camping table under Class B+ motorhome awning

How Do You Lubricate An RV Holding Tank Valve?

Lubricating an RV holding tank valve is another job that is relatively easy and costs very little money.

It involves disconnecting the gate valve from the drain pipe (be sure to wipe/clean around the seals), spraying a proper lubricant on it, such as Blaster White lithium grease, and re-installing it.

If you don't want to remove the waste gate valve assembly, here's an easier method.

Drill a small hole in the gate valve and spray grease inside that area. The below video shows this better than we can explain it:

What Is The RV Black Water Tank Valve?

The black tank holds only waste that goes down the toilet, including solids and liquids.

So, your black tank holds sewage. The RV sewer gate valve stops the sewage from draining out until you are ready to dump.

What Is The Grey Water Valve On An RV?

The grey water valve holds back the waste contents of the grey tank until you are ready to drain it.

The grey tank holds all liquids that go down your shower and sink drains.

Class C motorhome parked along Denali Highway Alaska

Should You Shut The Holding Tank Valve On A Camper?

Well, yes and no you should shut the holding tank of a camper.

If connected to a sewer drain at a campsite or a septic tank (at home, for example), you should NEVER leave your black tank valve open 24/7.

Only open it when you intend to drain the entire tank.

However, you can leave your grey waste tank open at all times.

It still isn't a bad idea to let the grey tank fill up now and then, so when you drain it, the force carries out any leftover bits and you don't end up with food particles building up at the bottom of the tank.


RV waste tanks have valves that hold the liquids inside the tank until you are ready to dump. They act as a door that keeps the wastewater in the appropriate tank until you wish to empty it at an appropriate dump facility.

Sometimes the door (RV waste water valve) has issues, causing nasty leaks to happen.

This is usually apparent when you take off the cap from your dump pipe and you're met with waste you weren't prepared for. Leakage should not happen when your valve(s) are working correctly.

Thankfully, it's not hard to diagnose and fix the issue, no matter what it is. Just be sure you address any problems that arise so your camping trip goes smoothly!

Kelly Headshot

I dedicated myself to living the full-time RV life for over 6.5 years, immersing myself in the unique quirks and joys of the boondocking lifestyle and gaining a wealth of knowledge and experience along the way. In December 2020, my business partner and I made the transition to part-time RVing, but in January 2023, we hit the road once again, this time in our trusty vans. My mission is to help others embrace the RVing lifestyle with confidence and excitement, armed with the knowledge and resources needed to make the most of their adventures. I believe that the more you know, the more you can truly appreciate and enjoy the freedom and flexibility of the open road.

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