Here's a pic of the waste valve on my '84 Allegro:I have a couple of problems. First, whatever style fitting that is won't accept newer hoses or caps. The only cap that will fit is the original, which has 2 tangs on it unlike new ones that have 4. I tried to use my brother's Rhino hose this past weekend (long story) and it wouldn't fit either.The other problem is the black valve is leaking significantly. And the old cap isn't holding it back.I'd like to replace that fitting with one that accepts newer hardware, but I don't know what sort of valve I'd have to get. The gray water valve is new (you can almost see it on the right). I don't have a lot of room to work with on the black water pipe. The valve is installed at the end of a 90-degree elbow. I'm afraid if I cut it off, I won't have enough pipe to install a new valve. Things would snowball out of control from there. I'm wondering if just that valve will come out and I can replace it with a new one? This wouldn't solve my fitting/cap problem but I have to stop that leak at a minimum.

The Valve and the end cap is a "Thetford". Tiffin probably still have the Thetford valves and caps. Doughttp://www.amazon.com/s/?ie=UTF8&keywords=thetford+valve&tag=googhydr-20&index=aps&hvadid=21986683404&hvpos=1t1&hvexid=&hvnetw=g&hvrand=14049421454271705916&hvpone=&hvptwo=&hvqmt=b&hvdev=c&ref=pd_sl_479fctbj4u_b

Can you take the old valve apart? What normally happens is some TP will get stuck in the groove and not allow the blade to fully close.

Replacing the valve is not that hard.When you replace it I would think you would be able to find the new style fitting.I know this is not the same vehicle but maybe this helps?Replaced both the gray and black water gate blade valves.

Jimmy, Dollars to donuts that is a Thetford valve. It should be held in place by 4 screws and be easily removed. Parts are available, but they are very proud of them. Don't order from Thetford unless you have a lot of time. They are real bad at shipping promptly - even when they already have your money. Just get to any good RV supplier and tell them you need the rebuild kit for a Thetford 3" valve. (Try Vintage Trailer) It will work unless that valve is old enough to be the stainless back side. I would doubt that. Unfortunately, all the newer valves use a different bolt spacing.I do not believe that the T was a Thetford product. The mated flange is definitely not theirs. It is also not Valtera. That being the case, I don't think you have a lot of choice here. What I would do (fortunately, I don't have to), is get a Valtera or other common bayonet flange, then measure to see if it will fit on with the existing ears are removed. Then, carefully saw off the ears and glue the new flange over the old. This may require that you trim the OD of the remaining plastic. I don't know what tools you have available, so I hesitate to suggest a method. Matt

Thanks all!It is indeed a Thetford valve. Says right on it. Now that the black tank is drained (another long story) I can open the valve and see what's going on. The rubber seal is all deformed - it's toast. It appears as if the blade is plastic.It would be cool if there was a Thetford-to-normal-bayonet adapter but I haven't been able to come up with one. Maybe hacking that one out is an option.If I replace the valve with a newer style, I'd have to hack the elbow off at the tank, which might not be the end of the world if I could slip a new elbow over the remnants. I'll have to hack away all that foam insulation to see what I'm dealing with.In the meantime, I'll look for a thetford rebuild kit. Might be the best short term solution.

Leaky Black Water Valve - what are my options? | Good Sam Community

18 Replies

turbojimmy
Explorer
Oct 28, 2014
All fixed. The Thetford rebuild kit was perfect. I replaced the deformed blade seal as well as the o-ring on the outlet. Lubed everything up with Vaseline. It's all sealed up nicely. The Thetford-to-Valterra adapter sealed up, too, and I have a Valterra cap on it. I also have a Valterra fitting on my hose now.

It was not a pleasant job. There was indeed some TP stuck behind the valve, but that wasn't the cause of the leak. I set fire to all of the tools and clothing that I used in the repair when I was done.

On to the new range/oven - UPS will be dropping it off tomorrow!
turbojimmy
Explorer
Oct 26, 2014
1984Allegro wrote:
On my 84 Allegro I just used a Thetford to Valtera converter piece I got off the shelf at my local RV store. It is inline and is only a few inches long.

Yep - it fit perfect. But I haven't fixed the leaky black valve yet. Not looking forward to it.
1984Allegro
Explorer
Oct 26, 2014
On my 84 Allegro I just used a Thetford to Valtera converter piece I got off the shelf at my local RV store. It is inline and is only a few inches long.
turbojimmy
Explorer
Oct 20, 2014
Okay - I got a box full of parts today. I had just replaced the gray valve so I didn't want to go through that hassle again. That new valve will come off with that Thetford bayonet fitting leaving me with just the black water slide valve.

So, the parts I got are:
- black water slide valve rebuild kit. It looks like what I need, assuming I can get the valve apart
- Thetford-to-Valterra adapter. It fits nicely.
- New Valterra cap w/ hose fitting for gray water. It fits the adapter nicely

When installed, it doesn't stick out too far. It looks good.

I also got a Valterra-style stinky slinky fitting that I can install on my existing hose (it's new, too). It will meet up with the aforementioned adapter.

All told, $48 including shipping. Had I put in new valves and a Y assembly, I'd have needed the hose fitting and cap anyway. So I'm about $30 in with the rebuild kit and Thetford-to-Valterra adapter.

If the rebuild kit doesn't work, I'm in for a lot more work but not a ton more $$.
rockhillmanor
Explorer II
Oct 15, 2014
Yeah, that's probably the best way to do it. I see different kinds of "y"s online that would work.

I've also seen the twist-on repair valves, too. But, I'd need an
adapter to go from the Thetford to the Valterra,
then twist on the repair valve. I think it would stick out too far by the time I was done with all of that.

No you don't have to do that.

I have valves that are marked Bristol on it. I was led to believe that ONLY a Bristol valve would fit in the assemble.

When I had to have the whole Y assembly replaced the service guy plunked down all the parts including a Valterra blade assembly.

When I pointed out that mine were Bristols and that the Valterra would not fit? He said that was years ago, now the Valterra fits ALL of them....he was right too it fit like a glove.

so don't be too quick to write that off.

Also I would call a mobile rv repair guy to do it. They see so many of these and can repair them in minutes. They also get the parts at wholesale and stock everything needed for the repair right on their truck.

What I found out by pricing what "I" would have to pay to buy 'all' the parts retail including the sleeves.....It was CHEAPER to have Mobile RV do the work while I watched. :B
turbojimmy
Explorer
Oct 14, 2014
Matt_Colie wrote:
Jimmy,

I see the real problem is that you don't (and I don't either) know what that bayonet flange you have is.... I have never seen one like it before. I can tell you it is not Thetford, Vaterra or Columbia. Those are the only three that I know how to buy.

Matt

So that's not a Thetford bayonet? Now I'm really confused. The cap and valve say Thetford on it, but it could be a long-discontinued style given the fact that it's 30 years old.

I may wind up hacking it all out after all.
Matt_Colie
Explorer II
Oct 14, 2014
Jimmy,

I see the real problem is that you don't (and I don't either) know what that bayonet flange you have is.... I have never seen one like it before. I can tell you it is not Thetford, Vaterra or Columbia. Those are the only three that I know how to buy.

Matt
turbojimmy
Explorer
Oct 13, 2014
rockhillmanor wrote:
They just cut off both pipes coming from the black and gray and installed a whole new Y assembly. You can pick the Y assembly up at any camping store or dealership. I installs just like a residential fix under a sink with a rubber sleeve and hose clamps.

That way you would have the correct fitting for the sewer hose too.

Yeah, that's probably the best way to do it. I see different kinds of "y"s online that would work.

I've also seen the twist-on repair valves, too. But, I'd need an adapter to go from the Thetford to the Valterra, then twist on the repair valve. I think it would stick out too far by the time I was done with all of that.
parkdep
Explorer
Oct 13, 2014
This works very well and installs fast Waste Valve
rockhillmanor
Explorer II
Oct 13, 2014
Just make sure to check the tabs on where they attach.

Turned out mine was leaking from cracked tabs. There were hair line cracks you could 'not' see but the water found it's way out thru them.

When we went to replace just the valve blade the tabs broke right off when we were unscrewing it. Mobile repair says he sees it alot because the assembly is 'suspended', moves, and takes a punch from the constant pounding driving down the road.

They just cut off both pipes coming from the black and gray and installed a whole new Y assembly. You can pick the Y assembly up at any camping store or dealership. I installs just like a residential fix under a sink with a rubber sleeve and hose clamps.

That way you would have the correct fitting for the sewer hose too.

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Leaky Black Water Valve - what are my options?

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