How To Fix Leaking RV Waste Water Valves

This post may contain affiliate links. If you purchase through these links, we may earn a small commission at no additional cost to yourself.

Leaking waste valves can be just about the nastiest issue you might be faced with as an RV owner.


The first sign there is a problem will be when you remove the black cap in preparation to drain your waste tanks.  If you’re greeted with about a half gallon of waste water as soon as you loosen the sewer cap, then one of your dump valves has lost its ability to contain the water in the tank.

The next step is to determine which of the dump valves is leaking.


How To Determine Which Valve Is Leaking

The standard configuration for waste tanks will have 2 wastewater valves equipped with “T” handles for opening and closing.  One will be large, about 3 inches and the other will be smaller at about 1-1/2 inches.

An occasional RV will be found that has a 3rd dump valve, and even 2 separate dump hookups.  It’s hardly an owner-friendly arrangement, but I have seen it.

To determine which valve is leaking, you should have your RV waste tanks empty.  With the wastewater valves closed, and the black cap off, place a 5-gallon bucket under the sewer drain port.

Run about 5 gallons of water into the gray water tank through the kitchen faucet. That will be the smaller wastewater valve.  Let it sit for awhile and watch to see if any of the water drains out into your bucket.  If you feel that 5 gallons isn’t a good enough test, run a bit more.  If you determine that particular valve isn’t leaking, you can drain the tank into your bucket and dispose of it.

Next, repeat the same procedure with the black water tank by pouring 5 gallons into the RV toilet.  Again, let it sit for awhile.

TIP: Sometimes toilet paper hangs on the seal or blade of the black water dump valve causing a temporary leaking situation.  This happened to me just this past weekend when we went camping.  All that’s needed to clear this problem up is to flush the tank, and work the wastewater valve open and closed a few times to clean the valve seat.


How To Replace The Leaking Valve

Once you’ve determined which RV dump valve is indeed leaking, you can prepare to disassemble the valve by draining both waste tanks completely.

The waste water valves are designed to be somewhat easily disassembled and replaced.


You will find 4 smaller bolts that run through the outer flanges and the actual valve portion of the dump valve.  Remove the 4 bolts, and separate the sections so that the “T” handle and attached valve drop out of the center.

Replacement waste water valves are available on the Internet and at RV dealerships.  They’re the same on practically all RVs — so matching up is simply a matter of, “Is it the small valve, or the large valve?”

Reassembly is easy.  Here’s how to do it.  The most important thing is to make sure that the new seals between the sections are in the correct position.

Once you’ve got it all back together, rerun the water test to make sure you have solved the problem.


A Word Of Caution…

You may be tempted to let a leaking waste water valve problem go on for awhile, because this type of DIY repair just sounds so unpleasant.

But this will only compound your problems — especially if the issue is with the black water dump valve.

With a leaking RV wastewater valve, even if it’s running down the sewer hose and into the dump station at your campsite, you are losing the liquid that is being sent from the toilet.  At the same time, the solids are staying put and building up in the tank as the water will quickly run off.  In a very short period of time, the black water tank will become loaded with solid material that will set up like solid clay.  Then, you’ll really have a mess to deal with!

If you take care of the leaky valve situation when it develops, then the project really isn’t that bad to deal with.  Just be sure, when you’re all done go wash up real good before you do anything else.


More About RV Waste Water


I’ve been involved in RVing for over 50 years — including camping, building, repairing, and even selling RVs and motorhomes. I’ve owned, used, and repaired almost every class and style of RV ever made. I do all of my own repair work. My other interests include cooking, living with an aging dog, and dealing with diabetic issues. If you can combine a grease monkey with a computer geek, throw in a touch of information nut and organization freak, combined with a little bit of storyteller... you’ve got a good idea of who I am. To date, I've shared my RV knowledge in over 300 articles here at The Fun Times Guide! Many of them have over 25K shares.

10 thoughts on “How To Fix Leaking RV Waste Water Valves

  1. Where can you get the adaptor part that the waste water valve bolts to. ( i.e. the abs fitting that takes you from your 1-1/2″ abs pipe to the valve body)

    1. Jokeria, I believe this link to is the part your looking for.   Otherwise Camping World will likely have what  you need too.

  2. Dbdb1972, I assume you’re referring to the dump valve seals.  If there was any damage to the blade, or the seat where the blade goes, it will still leak with new seals.  The whole valve assembly can be replaced, See this link:  If you did install a new valve assembly and the leakage is between the valve and the fitting attached to it, you might try applying some silicone caulk to the o-ring before you bolt the sections together.  

  3. Mr. Curits,

    Sorry I should have put a picture with this.  My finger is pointing at where the black valve and the waste port connecter is located.  How do I make the two sit tightly enough together that the water does not leak out of this area.  There is no coupler, just held together by tension.

    1. Jnhawes395,  Great picture, very helpful to let me understand the issue.  I’m assuming you haven’t disassembled the setup at this point.  I say this because I think the problem lies within the flange you’re pointing at.  I tend to believe there is a flange on the inside of that connection that is cracked or broken.  Tension isn’t enough of a connection, I’m pretty sure it’s not a compression fitting, but not positive.  I would unbolt both the small and large connections and find out what’s going on rather than apply any kind of sealant to the outside.  If it is a broken fitting any RV dealer should be able to supply or order a replacement.  You might even find one on or other RV parts sources on line.

  4. When we try to dump the waste out of the waste valve everything comes out even thow we didn’t pull the lever

    1. Jason, Pretty sketchy on your description of the problem but if you mean when you remove the cap the wast tank empties before you even pull the handle out the problem is with the blade valve. It’s apparently damaged or at least it’s stuck open if the handle won’t go back in. Your only choice is to take it a part and see what’s going on. Remove the 4 corner bolts and the valve assembly will slide out of the fittings.

  5. I’m attempting to replace the gate valve in my 2012 Bullet 246RBS. I have the four bolts out but now I’m having trouble getting the two sides split far enough to allow the old valve to drop out. Any thoughts how I can get these to separate?

    1. Be a little less gentle. It may take a bit of prying but you don’t really need to separate them very much to wiggle the valve out of there.

Leave a Reply

Your email address will not be published. Required fields are marked *

Recent Posts