Add fitting to black tank?

[richard5933]

We have two tanks on our coach - a 90-gallon freshwater and a 90-gallon combined gray/black waste tank. The conversion was done by Custom Coach in 1974, and for whatever reason they used a 2" outlet on the black tank, which is controlled by a pneumatically-controlled discharge valve. The outlet flange on the black tank is bolted on using gaskets. The tank appears to be made from polyethylene, although obviously it's older and has a slightly different color than modern ones. Things work pretty well, and with the combined gray/black tank things are usually liquid enough to empty okay.

Here's the problem: The discharge valve is starting to let liquid seep past it and down the discharge hose. It's not seeping all that much right now - maybe a few drops a week. But, the tank is not full at the moment and I suspect that things will get worse when there are 90 gallons of liquid pushing behind it. (There are no leaks external of the valve - the green crud is corrosion from condensation)

Possible solutions:

     1. Continue using a cap on the outlet to catch the drips between one dumping and the next. Messy and not ideal.

     2. Repair the valve. It's a bronze valve that theoretically can be opened on top, but I cannot get the top to spin off. I'm sure if I really bear down on it the thing will open, but I'm afraid that I'll damage the bulkhead connection in the process.

     3. Install a secondary (modern) discharge valve downstream from the current valve. The discharge valve has about 18" of 2-3/8" rubber hose after it that leads to the point where the discharge hose connects outside. I could cut out a portion of this rubber hose out and install a secondary gate valve. This would catch whatever gets past the original valve.

     4. The more dramatic step would be to remove the bulkhead fitting and replace it with a 3" fitting. Then I'd be able to retrofit a modern discharge valve. My concerns/questions about this:

          a. Is it possible to retrofit a bulkhead fitting on an existing tank?

          b. Are bulkhead fittings still made that can be bolted onto a tank instead of doing a spin-weld? If so, can they be mounted blind (without having full access to the inside of the tank)?

     5. Even more dramatic, get a new (custom made) tank with modern fittings. My tanks are very easy to access. While it would take a while to reconnect the fittings and install the necessary adapters, all parts are easily accessible in the bay without being a contortionist and without taking anything else apart.

Right now I'm leaning towards #3 above. It would help ensure that nothing leaks out and would make dumping cleaner than it is right now. However, not sure it's worth the effort and I'm wondering if it's better to just bite the bullet and have a new tank made.

Thoughts? Suggestions?

 

[hermanmullins]

I go for #3 also. If you have room for another valve that would be the easiest solution to me.

Herman

[wildebill308]

There is a possibility the only thing wrong is some debris in the sealing ring on the valve. With everything drained and rinsed take the valve apart and look. It should be possible to loosen the valc top without damaging the tank seal by using a impact wrench to break the top loose.

Put a dab of anti seize on the threads when you go back together.

Bill

[richard5933]

1 hour ago, WILDEBILL308 said:

There is a possibility the only thing wrong is some debris in the sealing ring on the valve. With everything drained and rinsed take the valve apart and look. It should be possible to loosen the valc top without damaging the tank seal by using a impact wrench to break the top loose.

Put a dab of anti seize on the threads when you go back together.

Bill

That was my first thought too. Problem is getting the top of the valve off, as it doesn't seem too inclined to move. The flange connection to the tank is a bolt-on one and any movement in the pipe causes the flange to want to flex the side of the tank.

Right now the tank is basically empty other than a few gallons of RV antifreeze, so it would be a great time to try and clean the valve if I can get it apart. My biggest nightmare would be causing a leak at the flange while fixing the valve, and then I'd be looking at replacing the entire tank. Not something I really want to do right now. Hence my thought to just add another valve downstream until I came up with a better plan.

How would I get the top of the valve off with an impact wrench? Huge socket? I've just been using an adjustable spud wrench so far.

[wildebill308]

Yes a good 1/2 or 3/4 drive impact and a socket should work without messing up the flange.

Bill

[manholt]

Since all the corrosion needs to come off, why not remove the valve first, then work on the top of valve?  It may not even need to come off, unless you have a drawing of the inner parts of the valve!  In the picture, it looks to me that the valve and tank fitting are 2 separate parts. IMHO

[richard5933]

3 hours ago, manholt said:

In the picture, it looks to me that the valve and tank fitting are 2 separate parts

If you look at the photo where the current valve meets the flange, you'll see that the way the valve would come off is by spinning the entire valve. In order to do that, I have to pull the tank (or at least lift it a few inches to give clearance for the valve to rotate). Once I separate all the connections to the tank I'm just asking for trouble, since it's inevitable that at least one of them will either be stuck in place and refuse to come off easily. Then I'll have multiple problems and possible leaks. My experience has proven that once you start messing with old plumbing (43+ years in this case) problems multiply quickly. Even putting an impact wrench to the top of the valve to get it open scares me, since the momentary torque on the valve body might be enough to break the seal between the flange and the tank.

All this is why I'm looking at only few options until I'm able to replace the entire tank.

My first choice is still to add a secondary valve downstream of the current one for now.

However, if someone knows of a method for adding a bolt-on flange to an existing tank when there is no access to the back side of the flange I'm all ears. The way the tank is situated, there is no physical way to reach the back of the flange area other than through the flange itself. What I'm imagining is some type of bolt-on flange where the inside portion is in two pieces and can be held in place by reaching through the new flange while the flange/gasket/tank/gasket/backer are all bolted together. Maybe I'm dreaming, but I can't be the first person to ever have to replace a black tank flange.

[hermanmullins]

Richard,

Even if you could remove the flange what are the possibility of damaging the flange and having to replace it? It could be one very hard to find item. I am with you #3. But I would if possible replace the hose and clamps. 

When messing with the sewer system all ways remember to tilt the tank to opposite direction. 

Luck to you.

[manholt]

Richard.

I agree, to many variables.  The material of the tank itself, reminds me off having the same on a 1974 and 1981 Class A.  The fresh water tank was under the plywood that held the mattress of the bunk bed (back then, no queen or king bed).  Your black tank has horizontal metal reinforcement on the inside. 

The good news, is that if the tank gets a tear in it, or a hole...use a solder iron!

Carl 

[richard5933]

Added a secondary valve to the waste discharge for now. Hopefully in the fall I'll be able to swap out the tank for a new one, and at that time switch over to a modern 3" discharge valve.

Since we only have the 2" discharge right now, I've also added a water jet inside what used to be the clean-out cap on the final 'T' fitting. This should make it easy to break up anything that clogs the valves or discharge pipe. Under the 'T' fitting I connect a normal/modern flex hose to dump. I'm hoping that the combined gray/black water tank should keep things liquid enough to flow through the 2" valve. Since this has worked for 43 years I assume that it will be able to keep working for a few more months.

[desertdeals69]

Looks good, hope it works as planned.

[manholt]

Looks like a good, inexpensive solution.  Not to get personal, but why wait till fall?  

[richard5933]

10 minutes ago, manholt said:

why wait till fall?

Simple - budget for upgrades is shot for this season. I did a full upgrade of the electrical bay as well as upholstery, carpet and some interior lighting. Also did quite a bit of unseen work on the chassis and coach systems for reliability. I'm holding onto enough of a cash buffer to cover things that may go wrong while traveling this spring/summer, and then in the fall will pick up again with upgrades once the accounts have a chance to recover some.

Plans for this fall so far include upgrading the fresh water and waste water tanks as well as having Jake Brakes installed. Might also get started on solar install if there is room in the budget, otherwise that will wait until next spring.

[richard5933]

Update on this issue...

We've used the coach a few times since I added the extra valve to the black tank outlet. Today was the first time to dump since the new valve was put in place. (There are only two of us, and we are very frugal with our water use.)

I've been running with the end plug on the discharge pipe just in case the new valve didn't cure the problem. It didn't. Glad I took precautions.

In spite of the original valve being closed AND the new Valterra plastic valve being closed, there was still about 1/2 to 1 cup of liquid in the pipe downstream from the two valves. Was wearing gloves at the time, and the cap is under the floor of the bay, so no biggie. But, I'd sure like to have this thing work properly and be more sanitary when dumping.

Not sure what to think other than the new Valterra valve is just defective, since it obviously should have been able to seal against this liquid since the old valve was clearly still holding back the majority of the pressure from the 50+ gallons of waste water. I do have another Valterra gate valve I could try - this one with a plastic body as well but with a stainless gate instead of the plastic one.

Any thoughts?
 

BTW, the combined black/gray dumped with absolutely no issues through the 2" outlet. My guess is that having a combined tank is what makes the smaller outlet possible.

[manholt]

I'm not a fan of plastic valves.  I replaced all I could, with brass ball valves and some SS.  I currently have a gate valve that won't close completely on my 3".  Off course, it's the black water.  I don't like the push/pull gate valves for gray or black...still looking for an alternative.  There has got to be one somewhere!

[manholt]

Since you have a combo B/G tank, 2" should be enough, I would prefer a 3" or larger to prevent solid build up and make clean out easier!!  My thinking is that every coach should have a combo!