Repairing cracked black water tank
From the day we bought good old Mabel, she's had a leaking black water tank. A PO somewhere along the line did a very poor job of repairing what I think is a crack at the valve fitting with some fibe...
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Good progress on the black tank repair this weekend.
I cleaned things off, drilled the ends of the crack (it was all the way around the bottom), beveled the whole crack and welded the bottom shut. Then I welded in the reinforcing SS mesh and welded more material in over the top. I finished by welding material into the open crack so that it was just a little proud of the surrounding material. The plug I cut out of the tank when I put in the flushing system was actually enough material to do all the work. I can still buy some LDPE to cover the whole thing if I want, but the repair looks/feels solid. I also ordered a new blade valve and will install that before I try loading it up with water for leak testing.
I believe I also identified why it broke in the first place. Looks like a PO tried taking the tank out and a mounting bolt for a support strap is spinning (was probably welded in). I cannot get to the back of that bolt to hold it, so the locknut can't come off, or go further on. That leaves about 3-4 inches of play between the retaining strap and the tank. With that much movement, the tank can really sag when full. I think that the tank sagged, put strain on the outlet and cracked the bottom open. I have put in some rolled vinyl (minimal compression) to take up that slack for now. I will have to remove the fiberglass side skirt in order to have proper access to try and rig up an alternative mounting for the support strap, though. On the plus side, the outlet tube looks like it is well sealed and I won't have to dismantle/clean/reseal that part.
I will update after I install he replacement valve and leak test.
Jose
I cleaned things off, drilled the ends of the crack (it was all the way around the bottom), beveled the whole crack and welded the bottom shut. Then I welded in the reinforcing SS mesh and welded more material in over the top. I finished by welding material into the open crack so that it was just a little proud of the surrounding material. The plug I cut out of the tank when I put in the flushing system was actually enough material to do all the work. I can still buy some LDPE to cover the whole thing if I want, but the repair looks/feels solid. I also ordered a new blade valve and will install that before I try loading it up with water for leak testing.
I believe I also identified why it broke in the first place. Looks like a PO tried taking the tank out and a mounting bolt for a support strap is spinning (was probably welded in). I cannot get to the back of that bolt to hold it, so the locknut can't come off, or go further on. That leaves about 3-4 inches of play between the retaining strap and the tank. With that much movement, the tank can really sag when full. I think that the tank sagged, put strain on the outlet and cracked the bottom open. I have put in some rolled vinyl (minimal compression) to take up that slack for now. I will have to remove the fiberglass side skirt in order to have proper access to try and rig up an alternative mounting for the support strap, though. On the plus side, the outlet tube looks like it is well sealed and I won't have to dismantle/clean/reseal that part.
I will update after I install he replacement valve and leak test.
Jose
