How to Replace Leaky RV Waste Dump Valve and Save on Shop Repair Bill

It’s a stinky job, but someone has to do it.

Replacing a leaky RV waste dump valve is easier than it sounds. The most difficult part may actually be identifying which valve is leaking if you have multiple grey water tanks. Identifying black water should be easy.

We produced this quick video to show how simple it is to swap out the gate valve on your waste water pipe. Read on for helpful tips to identify the faulty valve and make the job go quickly.


How to Identify Leaky RV Waste Dump Valve

If you have water accumulating in your RV’s waste water pipe, you likely have a leaky gate valve, also referred to as a knife valve. When you dump your tanks, make sure all water is done dripping before replacing the cap. A small amount of water dripping out the next time you dump is to be expected, but if more than a cup or so spills out the next time you remove the cap one of your valves is probably leaking. The valve may have debris stuck in it, or a seal may have been dislodged or gone bad.

Black water should be easily identifiable, and unless you have more than one black tank you will immediately know which valve needs to be replaced. In our case, we have two grey tanks and the water building up in our pipe between dumps was coming from one of them. You may be able to identify kitchen water or bath water, but if not you have a few options.

  1. Rinse both tanks thoroughly and put some food coloring in one of them. Allow ample time for water to accumulate and remove the waste water cap to see what color the water is.
  2. Leave both valves open overnight or long enough for the pipe to drip completely dry. Close one valve and leave the other open. Fill the closed tank with water and wait overnight to see if water gathers in the pipe. Repeat for other tank if not to confirm leaky valve.
  3. Replace both valves.

How to Replace Bad RV Waste Tank Gate Valve

Anyone with the slightest mechanical capability and the right tools should be able to quickly change the gate valve on the pipe connected to an RV’s waste tank. The most time consuming task may be accessing the valve if your tanks are fully insulated like ours are. Use the following tips to make this repair job go smoothly or provide your own with a comment below.

  • Identify which valve is leaking. See tips above.
  • Locate and visually inspect the faulty valve to identify the correct size, likely 1 1/2″ or 3″.
  • Determine what tools you will need, probably a crescent wrench and/or socket set and screwdriver.
  • Vinyl gloves and protective eyewear may prove helpful.
  • Completely drain all waste water.
  • Remove handle from valve extension rod first if it extends through the RV chassis or frame.
  • Remove four bolts holding valve in place between the two waste pipes.
  • Remove seals if they did not come out with valve.
  • Clean any debris out from in between the two pipes to ensure new seals will seat firmly in place.
  • Lubricate seals with Vaseline to aid in alignment and hold them in place (optional).
  • Place new seals securely onto ridges on the waste pipes.
  • If applicable, place valve slider extension rod through hole in frame.
  • Slide new valve in place ensuring seals fit snugly into grooves on valve.
  • Make sure seals do not fold or dislodge when aligning the new valve.
  • Loosely replace bolts and ensure that seals are still in place.
  • Tighten bolts to secure valve in place. Do not over-tighten.
  • Fill tank with water and check for leaks before testing valve.

Stay tuned for more helpful tips and videos!


5 thoughts on “How to Replace Leaky RV Waste Dump Valve and Save on Shop Repair Bill”

  1. HI JIM! <>



    • Sounds like you need to get under there and visually inspect the waste valve. Make sure the rod is attached to the blade. If it’s operating but not dumping it is either broken inside and needs replacement or you have a blockage somewhere. Good luck with that!

  2. Thanks Jim! At the time I didn’t have washers, so I improvised with a small piece of twig… it works, but as I said, there is still a small leak. I’ll try washers when we next move camps.

    The seal ridges were clean, I took it apart to check when I first saw the problem.

    Replacing the pipe ends may come later. First I’d try the washers, and possibly a different valve. Replacing the pipe ends sounds like I could create a bigger problem if I don’t do it just right.

  3. I did this to ours about 6 months back. The new one however has a bit of a problem. There are two rubber gaskets which hold the valve tightly. If I tighten the 4 bolts down too tightly, the gaskets won’t allow the sliding mechanism to close. Instead it gets stuck on the rubber gaskets and doesn’t close fully. I had to back off the tightness of the 4 bolts in order to get the valve to close.

    Have you seen this happen before? It doesn’t leak when closed, but when dumping sometimes, it can drip from the valve. Any tips on fixing this odd problem?

    • Interesting, i didn’t encounter anything like that. If I did, I might add a small washer to each bolt so they could be tightened without crimping the seals together too tight. i would fear loose bolts but come out in transit easier.

      I’d also ensure the ridges that hold the seals are totally free of any debris or corrosion that might be causing the extra pressure on them. Finally, I would replace the pipe ends/brackets where the valve attaches.

      Good luck and thanks for asking!


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