Black tank leaking only when valve is open

[britt]

Hello everyone,

Hoping somebody can help pinpoint a black tank problem we are having with our 1969 Overlander.

The black tank itself holds water fine, but when we go to empty it the second we open the valve we get waste that flows out from the bottom- and not just a small leak but full on gushing, so much so that barely any of it even makes it to the waste hose.

I've searched the forums and can't find any other threads that have this same issue. Plenty of people with leaky valves, but I assume if it was just a leaky valve wouldn't it be leaking the whole time rather than just when we empty it?

If it's a bad seal wouldn't the leak just be minor rather than a heavy flow?

We haven't attempted to repair anything yet - thought I would see if anybody has any wisdom to share before we make any attempts.

Thanks in advance!

Kind regards,

[1973Argosy]

Sounds like the discharge pipe may have frozen and ruptured down stream of the valve. If the valve were bad it would leak all the time as you assumed.

[Foiled Again]

Agree with 1973argosy. Use your cell phone camera to examine the underside of the pipe to check for a split... keeping it well to the side if you open the valve!🤣

Paula

[Lily&Me]

I was having this kind of leaking when my valve needed to be replaced.

That may be the problem, and easily enough fixed.

Maggie

[britt]

Thank you for the suggestions - we will have a look and thankfully the tank has been cleaned out which will make for much more sanitary conditions for finding and fixing the issue!

[Lumatic]

Originally Posted by britt

the second we open the valve we get waste that flows out from the bottom

From the bottom of what and where?

[perryg114]

Could be the valve housing is split as well. Might just be a rubber collar has come loose. Fill with bleach let is sit then flush and then you can mess with clean water to troubleshoot.

Perry

[britt]

After giving the system a clean with bleach we were able to access the valve housing and it appears it's as simple as a leaky seal between the discharge pipe and the valve. It looks like the PO had Modified the piping a bit and the gasket and seal they used is no longer holding up.

While the valve does appear to be okay it does seem to be very old - should we go ahead and upgrade it while we have access and it is cleaned out? Not sure how long these valves hold up but for the cheap cost of a valve system it seems like a good idea to just go ahead and replace it. Or...should we follow the old saying, if it ain't broke, don't fix it...?

[HiJoeSilver]

It really depends on the type of valve and how it's installed. I know the valves on my 74 and 79 were no longer available. Then you can get into adapters to fit new valves, and possibly new plumbing to make things fit.

[Lumatic]

Originally Posted by britt

it seems like a good idea to just go ahead and replace it. Or...should we follow the old saying, if it ain't broke, don't fix it...?

The gate valve on a 69 is probably a Thetford. You can still get them but they are getting harder and harder to find. Vintage Trailer Supply has them. The industry trend is Valterra. Thetford is glued which means you have to cut them out. Valterra is screwed in. Both can last for decades. All sewer hoses have Valterra fittings. There is a Thetford to Valterra adapter. If you have a T where the grey water enters the main sewage discharge line above the valve, they also are very hard to find.

[Foiled Again]

Your choice, but my 2 cents is - go with new valterra valves and replace the gray one while you are in the neighborhood - how ticked would you be if the gray one failed on your next trip? Even if you have to replace everything from the tanks to the hose fitting, you are DONE. You are #1 at dealing with #2.

Paula

[1973Argosy]

Originally Posted by Foiled Again

Your choice, but my 2 cents is - go with new valterra valves and replace the gray one while you are in the neighborhood - how ticked would you be if the gray one failed on your next trip? Even if you have to replace everything from the tanks to the hose fitting, you are DONE. You are #1 at dealing with #2.

Paula

It's a 1969 trailer. No gray tanks till 1974 unless added as aftermarket.

[HiJoeSilver]

No two tanks forgot about that. That's definitely easier for the swap. Getting all the piping between two tanks can be tough. I'd swap it out with a valtera.