There is seepage at the top of my black tank right where the toilet drain hooks to the tank. It leaks from the bottom side of the flange where it meets the top of the tank. I have some ideas but am not sure of the best path. thanks in advance, Bob

Find a local plastic welder and have him/her look at it.

bob b wrote:There is seepage at the top of my black tank right where the toilet drain hooks to the tank. It leaks from the bottom side of the flange where it meets the top of the tank. I have some ideas but am not sure of the best path. thanks in advance, BobYikes. Have heard of people cutting open the floor to access the joint to remove the old pipes and doing a better job of plastic welding. Depends on how much you want to do of course and how talented you are with construction.If you can reach the outside of the joint from topside or below, there are clamp on rubber devices to stop leaks. Check at Home Depot and the like. If there's no room, you might have to put an interior sleeve inside the drain...assuming there aren't too many bends and such.Whatever you end up doing, let us know what you came up with.

If you still have the 22 year old Tiffin, then the BEST fix is a tank replacement. On your model is the tank mounted outside under the rear frame or is the tank mounted inside the frame rails with the exit fittings and valves inside the water bay compartment? Tanks that old rarely will be able to be Plastic welded and JB weld or other type heavy duty glues and adhesives rarely will stick to the tank. The area you are talking about is a hi stress area that is extremely difficult to repair and stay repaired. Most of our local Plastic welders will NOT work on RV tanks installed. They want the tank removed before they will attempt a repair, Since they require the tank to be removed, it is crazy to repair it. Just replace it with a new tank. Tiffin does have older tanks in stock. You need to contac Tiffin. Doug

dougrainer wrote:If you still have the 22 year old Tiffin, then the BEST fix is a tank replacement. On your model is the tank mounted outside under the rear frame or is the tank mounted inside the frame rails with the exit fittings and valves inside the water bay compartment? Tanks that old rarely will be able to be Plastic welded and JB weld or other type heavy duty glues and adhesives rarely will stick to the tank. The area you are talking about is a hi stress area that is extremely difficult to repair and stay repaired. Most of our local Plastic welders will NOT work on RV tanks installed. They want the tank removed before they will attempt a repair, Since they require the tank to be removed, it is crazy to repair it. Just replace it with a new tank. Tiffin does have older tanks in stock. You need to contac Tiffin. DougI think the OP's profile is out of date. He also posted this question on TRVN, and he shows having had a 1996 Bus but now has a 2006. However I don't think this changes the validity of your suggestions.

When I remodel'ed our older rig, I had to create a new entry to the tank. They do make rubber gaskets for that junction. Not sure it applies to your situation, but just an idea.

Post subject: How do I fix a black tank leak? | Good Sam Community

Gjac
Explorer III
May 19, 2018
If I understand your post, the seepage is in the flange area where the 3 in toilet pipe attaches to the top of the black tank. Can you tell if it is a crack in the tank, flange or pipe? Or is it a bond separation between the flange and the top of the tank? When you say seepage it does not sound like a large crack is that correct? Yes ABS and other plastics can be difficult the bond but if you use a solvent like MEK or acetone the solvent will chemically react with the surface and prepare it for bonding. There is very little water pressure if any at the top of your tank so I would not worry about getting a high strength bond. On a 1996 MH I would solvent wipe the area real good several times and use Goop or Shoe Goo around the flange area. The key is not the bonding material that you use but how you prepare the surface to be bonded.
turbojimmy
Explorer
May 18, 2018
Here's my original thread.

Plasti-Mend Thread
turbojimmy
Explorer
May 18, 2018
BobGed wrote:
CLICKY

Thanks! I hate when I forget to do that.
BobGed
Explorer
May 18, 2018
turbojimmy wrote:
This stuff is amazing:

http://www.plasti-mend.com/cart/index.php?route=product/category&path=59

The 34-year-old black tank on my Allegro had some serious damage to the corner of it. An old repair finally failed so I bought this kit. Whatever it is, it kind of becomes one with the existing plastic. Read the history of the company - it's interesting.

The catch is that you're going to have to be able to get at the area you want to repair.

CLICKY
turbojimmy
Explorer
May 18, 2018
This stuff is amazing:

http://www.plasti-mend.com/cart/index.php?route=product/category&path=59

The 34-year-old black tank on my Allegro had some serious damage to the corner of it. An old repair finally failed so I bought this kit. Whatever it is, it kind of becomes one with the existing plastic. Read the history of the company - it's interesting.

The catch is that you're going to have to be able to get at the area you want to repair.
wa8yxm
Explorer III
May 18, 2018
One of my favoite adheasive sealers is GOOP. in fact that is what I used installing the Tornado flush device. ..13 years ago. .Still not leaking.

Another product I purchased for a totally DIFFERENT job is Flex Seal.. THough I bought it for one job. and it worked well.. I had some damage to the squirt gun (Windshield washer) tank on my Car.. It sealed that up right well too.. Multiple coats.
T18skyguy
Explorer
May 18, 2018
When I remodel'ed our older rig, I had to create a new entry to the tank. They do make rubber gaskets for that junction. Not sure it applies to your situation, but just an idea.
BobGed
Explorer
May 18, 2018
dougrainer wrote:
If you still have the 22 year old Tiffin, then the BEST fix is a tank replacement. On your model is the tank mounted outside under the rear frame or is the tank mounted inside the frame rails with the exit fittings and valves inside the water bay compartment? Tanks that old rarely will be able to be Plastic welded and JB weld or other type heavy duty glues and adhesives rarely will stick to the tank. The area you are talking about is a hi stress area that is extremely difficult to repair and stay repaired. Most of our local Plastic welders will NOT work on RV tanks installed. They want the tank removed before they will attempt a repair, Since they require the tank to be removed, it is crazy to repair it. Just replace it with a new tank. Tiffin does have older tanks in stock. You need to contac Tiffin. Doug

I think the OP's profile is out of date. He also posted this question on TRVN, and he shows having had a 1996 Bus but now has a 2006. However I don't think this changes the validity of your suggestions.
dougrainer
Nomad
May 18, 2018
If you still have the 22 year old Tiffin, then the BEST fix is a tank replacement. On your model is the tank mounted outside under the rear frame or is the tank mounted inside the frame rails with the exit fittings and valves inside the water bay compartment? Tanks that old rarely will be able to be Plastic welded and JB weld or other type heavy duty glues and adhesives rarely will stick to the tank. The area you are talking about is a hi stress area that is extremely difficult to repair and stay repaired. Most of our local Plastic welders will NOT work on RV tanks installed. They want the tank removed before they will attempt a repair, Since they require the tank to be removed, it is crazy to repair it. Just replace it with a new tank. Tiffin does have older tanks in stock. You need to contac Tiffin. Doug
Jim
Explorer
May 18, 2018
bob b wrote:
There is seepage at the top of my black tank right where the toilet drain hooks to the tank. It leaks from the bottom side of the flange where it meets the top of the tank. I have some ideas but am not sure of the best path. thanks in advance, Bob

Yikes.

Have heard of people cutting open the floor to access the joint to remove the old pipes and doing a better job of plastic welding. Depends on how much you want to do of course and how talented you are with construction.

If you can reach the outside of the joint from topside or below, there are clamp on rubber devices to stop leaks. Check at Home Depot and the like. If there's no room, you might have to put an interior sleeve inside the drain...assuming there aren't too many bends and such.

Whatever you end up doing, let us know what you came up with.