Holding Tank Valve Repairs

Holding Tank Valve Repairs

So, if you have a travel trailer or 5th wheel, this is a pretty straight forward repair, but what about motorhomes? Not so much! In fact, it can be quite a task, and it’s NOT for the faint of heart or impatient! Most motorhomes have the tank valves way in the back of the water hookup compartment, thus making them almost impossible to change! There is a but… but if you know how to do it, step-by-step, it can be done in a single afternoon!

Dealer Price for my Coachman: $595.00
My cost for parts? A little over $32.00
Does that have you motivated? 🙂 Good, then keep reading!

Supplies needed for this repair: Socket set, two socket extensions, gloves, open end wrench set, Vaseline, two dump valves, bleach and water solution.


First let’s quickly get the trailers out of the way. On TTs and 5ers, this is a relatively simple job. Take out the four bolts on whichever valve needs changing, spread the pipe and remove the entire valve and replace. Simple!

Easy peasey, that is IF it doesn’t leak!! The biggest cry for help I have found on the Internet for the DIY guy or gal changing one of these valves is, “HELP, IT’S LEAKING!

Don’t worry! I gotcha!

There are two reasons a brand new valve will leak, both of them installation errors. The first is, the valve gasket was not greased. When I say grease, I use Vaseline. The second reason is, the valve was installed in the CLOSED position. Installing the valve in either the closed position, or with no lubricant, (most commonly both) will increase your odds of having a leaky install due to improper seal seating on one or both sides.

The dreaded motorhome!


So, if you’re unlucky, like I was, and the black tank valve starts leaking on the road, this is a temporary fix that actually lead me to write another article! I bought this twist on valve and had it delivered to the park the next day. Twisted it on and it solved my leak problem until I got home.

Once I got home, I took a look inside the water compartment and procrastinated as long as I could! 🙂 Looking inside the water compartment I almost cried! There was about four inches above and an inch below the valves and I thought to myself it’s going to take a contortionist to get in there!


Drain and flush

So the first step in doing this job is draining, flushing and sanitising the tanks. I wrote another article on this that should publish soon, keep an eye out for it! Once the tanks are clean and empty, open both valves. I decided that since they both original equipment and ten years old, I should change both and not have to worry about either of them for a long time. Opening the valves relieves some of the pressure on the bolts and makes them easier to take out.

Once the bolts are removed, pull the collar out of the way, pull the pipes apart slightly and remove the valve. I removed the right side gray water valve first, and then the left black water valve. Pull out the pipe tee. Next comes the cleaning. I used Zep mold and mildew remover, but you can just mix up some bleach and water, 1 to 1. Clean out the entire compartment and the fittings on the pipes.



Coat the gasket with Vaseline! Yes, you heard me right, Vaseline! The petroleum serves two purposes. It helps the gasket stick to the pipe while you install the valve, and makes sure the gasket doesn’t kink while you’re tightening the bolts!

I worked from left to right, attaching the gasket to the black tank lip, then positioning the valve in place with the lubed gasket on the other side, then adding the T fitting and collar, and then hand tightening the bolts and nuts, working from the top down.

Before I added the bolts and nuts, I moved the valve up and down to ensure it was seated properly. It would have been much easier if I had a helper, but then again, two people couldn’t access this small area anyway.


The finished product

So here is the finished product. I will say that getting the bolts and nuts on and tightened will take a lot of time and patience! For the right side, I actually had to ask Jesus for some help! Believe it or not, just bolting the two valves up took me 40 minutes! This is the hardest part of the job!

Once the left valve was on and tight, and before I added the T and the right valve, I tested the black tank, just in case! Using the Vaseline method virtually guarantees no leaks!

Don’t be afraid to take on this job! It’s easy and satisfying!

Twist on valve for temporary repair: $23.39 – Amazon Prime

Valterra T1001VPM Bladex 1-1/2″ Waste Valve Body with Metal Handle – $14.18 – Amazon Prime
(Gray Tank)
Valterra T1003VPM Bladex 3″ Waste Valve Body with Metal Handle – $16.95 – Amazon Prime
(Black tank)



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