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How to Replace an RV Waste Valve: Either Black OR Gray!

How to Replace an RV Waste Valve: Either Black OR Gray!

RV waste valve replacement is not something any RVer wants to think about. But occasionally, it becomes necessary. Fortunately, it’s a relatively easy repair, especially if you have a guide to follow.

This post outlines the steps for the DIY replacement of a black or gray waste valve. Not only are we giving you a step-by-step guide, but we’ll also provide a video for those who prefer to learn visually. Let’s get right to replacing a waste valve on an RV!

What Are the Symptoms of a Failing Gray or Black Waste Valve?

A couple of different symptoms may arise to indicate that you’ve got a failing waste valve.

  1. There is an occasional small drip from the handle (primarily when pulling it for dumping).
  2. Even though both valves are closed, a small amount of water accumulates behind the sewer pipe cap. You’ll notice some liquid when you open the sewer pipe cap before opening either your gray or black valve.

Note that the black and gray waste valves (sometimes called gate valves or blade valves) should seal completely so that no liquid is found when you open the main sewer pipe cap. If you have liquid present there, or if you see liquid dripping from the handle when you pull it to dump your tanks, your gray or black waste valve is not sealing anymore.

The easiest way to tell which valve is leaking is to use the sniff test. Gray water smells bad, but it doesn’t have the same sewage smell that liquid from the black tank does. Also, fluid from the black tank is likely to be darker (generally brown), while liquid from the gray tank should be lighter and more grayish.

So, you’ll need to use your nose and eyes to determine which waste valve needs replacing. Note that the steps for black tank valve replacement will be the same as the steps for gray tank waste valve replacement.

Where Are the Gray and Black Waste Valves Located on My RV?

On many motorhomes, the valves are installed right inside the water bay (so the handles are the standard handles that come on the black and gray valves without the need for extensions). On many other RVs, the valves are mounted just below the bodywork on the street/driver’s side, with the handles visible.

An RV hooked up to dump, showing where the tank dump valve is located

On this RV, you can see the tank dump valve located just below the body of the RV, easily accessible.

On other RVs (often travel trailers, fifth wheels, and even smaller motorhomes), the waste valves may be mounted further inboard… up and under the RV (and this can include being placed up above anything used to enclose the bottom of the trailer for better insulation, so this may need to be cut/removed for access). The manufacturer then installs an extension handle (in some cases, it’s a solid extension, and in others, it’s a flexible cable extension) to bring the pull handle out toward the edge of the RV for easier reach.

With this type of remote valve placement, there will be a couple of extra steps to replace the valve completely. So, if your RV is equipped with an extension, you’ll need to unscrew it from the waste valve and then remove the valve handle from the new replacement waste valve, and re-attach the extension once the job is done and the new waste valve is seated correctly and in place.

How to Replace an RV Waste Valve

Again, the following procedure will work for the gray or black water dump valve.

NOTE: in most RVs, the gray tank valve is likely to be a 1 ½” valve (because only liquids drain from that tank). The black tank valve will be a 3” valve (for solids to drain out). However, some RVs use a 3” valve for both, and there are also instances where one or the other of the two valves will be a 2” valve. For these reasons, it’s important to confirm which size you need before ordering and/or removing the failed valve.

Gather the Items You’ll Need for the Job

  • Rubber gloves
  • Appropriate size box or open-end wrench
  • Socket wrench/ratchet and appropriate size socket

We like the 3/8″ Dr. Spin Disk Ratchet Handle because it includes a “Spin Disk” that allows you to use your fingers to tighten and loosen nuts or bolts when there isn’t enough room to move the ratchet handle (very handy in tight spaces like RV water bays!).

Sale
Alltrade 641505 3/8" Dr Spin Disk Ratchet
  • 3/8" Dr. & bits 2-in-1 thumb ratchet
  • Spin disk on ratchet head for one-finger spin-down/off
  • Sponge and/or paper towels to absorb or wipe up any drippage (whatever you use, you’ll want to throw it away!)
  • Replacement gate valve (any of the following may be appropriate for your situation):

Valterra 1-1/2″ Waste Valve with Metal Handle (Gray Tank)

Sale
Valterra T1001VPM Bladex 1-1/2" Waste Valve Body with Metal Handle , Black
  • Bladex waste valve.Fit Type: Universal Fit
  • Use with GrenTec, Bladex, Valterra, Bristol, and Anonda valves

Valterra 3” Waste Valve with Metal Handle (Black Tank)

This one is like the one on our motorhome, where the blade valve is installed between two sections of plumbing, and there’s a separate piece further downstream toward the opening that acts as the attachment point for a sewer hose.

Sale
Valterra-T1003VPM Bladex 3-Inch Waste Valve Body with Metal Handle, Mess-Free Waste Valve for RV's, Campers, Trailers, Black
  • NO MESS: At-home RV body valve repair is mess-free for your convenience
  • VERSATILE: Bladex valve is compatible with GrenTec, Blade, Valterra, Bristol, and Anonda valves

However, if yours has the bayonet fittings right on the valve body, you’ll need to use this one instead:

Valterra 3″ Valve Body with/Cap

Valterra 3" Stainless Steel RV Waste Dump Gate Valve w/Cap (1)
  • THIS IS NOT A TWIST ON STYLE - This has a 3" Hub o the reverse side which is a glue on style.
  • GLUE ON Waste valve with 3" cap

Only in rare cases would the following product be the right choice, but we want to supply a link in case yours is this size (again, note that the 1.5” or 3” gate valves are far more common).

Valterra 2″ Waste Valve with Metal Handle

Valterra T1002VPM Bladex 2" Waste Valve Body with Metal Handle , Black
  • Bladex waste valve
  • Use with GrenTec, Bladex, Valterra, Bristol, and Anonda valves

Finally, many RV owners also find the following product very helpful. It can be used as a secondary blade valve, attached at the outlet where you’d usually attach your sewer hose, as a stopgap measure to keep tank contents from leaking until you can permanently repair it. Or it can be used as a failsafe, so there are always two gate valves between the tank(s) and the outlet.

Valterra T58 Twist-On Waste Valve

Valterra T58 Twist-On Waste Valve, Mess-Free Waste Valve for RV's, Campers, Trailers
  • No more mess with an old valve problem.Fit Type: Universal Fit
  • Twists onto your current waste valve

Empty the Black and Gray Tanks

Empty your RV black water tank and your RV gray water tank. If you need assistance locating a dump station, see our post on how to find an RV dump station near you.

PRO TIP: If possible, perform the waste valve replacement when you have the RV tilted away from the side of the tank that the valve is on to help ensure that any remaining contents in the tank don’t leak out while you’re working.

This may also help if you have to replace the tank valve without being able to dump the tank(s) first. For example, this could be the case if the blade valve fails in the closed position and won’t open. In this case, you may need to tilt the RV more significantly to keep tank contents from escaping when removing the valve. Either way, have a bucket handy!

Loosen the 4 Bolts that Hold the Old Waste Valve in Place

With the closed end of a box wrench holding the nut in place, use your socket wrench to loosen the four bolts on the body of the old valve.

Removing the bolts holding the old valve in place

On the left side of the screen, you see the location of two of the four buts & bolts that need to be removed. On the right, you see the closed end of a box wrench holding the nut in place while a socket and ratchet remove the bolt.

Remove the Old Waste Valve

Gently flex both sides of the drain plumbing to allow the blade valve body to be removed from between them. You can use your sponge or paper towel to clean up any dripping.

Remove the Old Rubber Gaskets and Set the New Gaskets in Place

Remove the old gaskets/rubber seals from each side of the open drain pipe. They may be stuck on either side or to the old valve body. Please make sure you locate them before proceeding so you know they’re not still stuck in place.

Open your new waste valve and set the new gaskets in place on either side of the blade. Alternatively, you can set the new gaskets in place on either end of the drain pipe before installing the new waste valve. Either way works. The most important part is to ensure the new gaskets/seals remain perfectly in place and don’t get twisted/pinched as you replace the waste valve.

Old gaskets on the left side of the screen and new gasket on the right.

On the left side of the screen, you see the old gaskets, one on each side of the drain pipe. On the right, you see our new waste valve. We are setting the new gaskets in place, one on either side of the blade. Alternatively, you can put the new gaskets on either end of the drain pipe before installing the new waste valve.

Set the New Waste Valve in Place

Being careful to keep the new gaskets in place and not pinched, gently pry the two sides of the drain pipe apart to give yourself room to set the new waste valve in place. Line up both ends of the drain pipe and the body of the new waste valve so that the holes for the bolts align correctly.

Install the 4 New Nuts and Bolts

Install the four new nuts and bolts using your box wrench and socket/ratchet. Ensure the new seals/gaskets remain perfectly in place and all pieces align so the bolts slide in easily and can be properly tightened.

Tighten each of the four nuts/bolts only loosely until all four bolts are in place and everything is aligned. Then, tighten down the nuts/bolts.

That’s it! Mission accomplished! Your new waste valve is installed.

Watch Our RV Waste Valve Replacement Video

To follow us as we install a new gray waste valve on our motorhome, check out our YouTube video and follow us step-by-step:

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Jim Wray

Wednesday 31st of January 2024

We have an added degree of difficulty on our 2020 Grand Design Imagine travel trailer. All dump valves use cable extension handles, but the valves are mounted above a belly pan and foam insulated. A great cold weather feature, but not so great for valve maintenance! I’ve received two quotes to replace the kitchen gray water valve with the cheapest being $600. Since I was able to work the valve open, I installed a twist-on gate valve as the primary tank valve.

Don't Let a Sticky Black Tank Valve Make for a Crappy Day! - Lower 48 In Tow

Monday 5th of October 2020

[…] RV Gray Valve Repair — REAL-TIME DIY Holding Tank Valve Replacement […]

Shari English

Wednesday 18th of September 2019

I have a question. Does the new valve have an obvious orientation, or can it go either way? Never replaced the valve, but just bought a 22 year old NASH and need to replace valves.

TheRVgeeks

Wednesday 18th of September 2019

Hi Shari. Good question! Ours did not appear to have any orientation... and the installation instructions didn’t indicate that there was any special way it had to go in!

bob g

Sunday 8th of September 2019

Thanks for the video. It's always good to see how someone else did it prior to tackling a task yourself. One suggestion I would add is to have a small catch pan of some sort under the pipe when removing the old valve. That way if you have a leak it won't get on the floor of the bay. I also would recommend a little plumber's grease on the seals and valve prior to install.

Lloyd Stanton

Monday 9th of September 2019

That was great. When can you come over and fix mine?

TheRVgeeks

Sunday 8th of September 2019

Good tips, Bob.

richard ackroyd

Sunday 8th of September 2019

You two probably already know this but for those who don't........ Before working on the black / gray valves dump the tanks with the wet bay side of the RV slightly lowered to get all of the contents out then raise that side of the RV to slightly higher than normal to stop anything dripping out when you take the valve (s) off.

Richard.

Lloyd Stanton

Monday 9th of September 2019

Good Idea!

TheRVgeeks

Sunday 8th of September 2019

Great suggestion, Richard. Never hurts to be REALLY sure the tanks are dumped fully before working on the valves!

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PLEASE NOTE: We're handy RVers, not professional technicians. We're happy with the techniques and products we use, but be sure to confirm that all methods and materials you use are compatible with your equipment and abilities. Regardless of what we recommend, consult a professional if you're unsure about working on your RV. Any task you perform or product you purchase based on any information we provide is strictly at your own risk.

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