Waste tank expansion (movement) on top side
Well, I had a real brain fart this past weekend....... Was setting up and hooked up the water thinking I was hooking up to the city water inlet. Instead, I had hooked up the water to the tank fl...
Forum Discussion
Okay,
I pulled the underbelly down to check things out. The tank is supported by supports on both sides (across the width of the trailer). The front brace is welded and the rear one bolted in place. Nothing was broken. The tank has lips molded in that sit on the braces.
I filled the tank again and found nothing looking wrong underneath. The toilet and vent pipe moved up again. But this time it seemed to be gradual. I think the time before, I thought it was sudden only because my foot may have slipped off the valve. The floor of the storage compartment also flexed upward significantly.
Taking measurements indicated that the supports underneath didn't move, but the tank did pull in a bit, away from the support.
Looking online it seems that 30 inches of water column creates about 1 psi of pressure and 120 inches is about 4 psi.
The tank seems to be made of a fairly thin plastic. Pushing on the bottom of the tank when empty moves it pretty easily.
My conclusion is that the build up in pressure (up to around 4 psi) caused the tank to expand like a balloon - top and bottom. Even pulling the sides in a bit.
There is some space between the top of the tank and the storage compartment floor. But the flange holding the drain pipe is tight against the floor so it pushes the floor up as soon as it starts to move.
I think originally, the resistance of the floor, the toilet flange bolts etc. held against the pressure until the flange bolts let go. They were only about 1/4" sheet metal screws into 1/2" plywood.
I ended up reinforcing the toilet mount by taking about a 12" square of 3/4" plywood, cutting a hole for the 3" drain pipe, cutting the drain apart, sliding the wood up underneath the bathroom floor and mounting it there with some screws. Then I went inside and drilled 1/4" holes through the flange mounting holes all the way through the floor and plywood. Then I put 1/4" x 4" bolts through and secured them underneath with fender washers and nuts. I reassembled the drain pipe with a couple of flex couplings.
I also put a clamp around the 1 1/2 " vent pipe to the side of the plywood support to give it some resistance to movement. Then I added a 1 x 2 furring strip to the edge of the storage compartment floor to stiffen it some. I screwed it into the front compartment vertical divider right at the bottom edge.
I don't know for sure if this is enough reinforcement to prevent all damage if the tank is overfilled in the future. But hopefully it will help.
I think the key thing is going to be to not overfill the tank again.............
I pulled the underbelly down to check things out. The tank is supported by supports on both sides (across the width of the trailer). The front brace is welded and the rear one bolted in place. Nothing was broken. The tank has lips molded in that sit on the braces.
I filled the tank again and found nothing looking wrong underneath. The toilet and vent pipe moved up again. But this time it seemed to be gradual. I think the time before, I thought it was sudden only because my foot may have slipped off the valve. The floor of the storage compartment also flexed upward significantly.
Taking measurements indicated that the supports underneath didn't move, but the tank did pull in a bit, away from the support.
Looking online it seems that 30 inches of water column creates about 1 psi of pressure and 120 inches is about 4 psi.
The tank seems to be made of a fairly thin plastic. Pushing on the bottom of the tank when empty moves it pretty easily.
My conclusion is that the build up in pressure (up to around 4 psi) caused the tank to expand like a balloon - top and bottom. Even pulling the sides in a bit.
There is some space between the top of the tank and the storage compartment floor. But the flange holding the drain pipe is tight against the floor so it pushes the floor up as soon as it starts to move.
I think originally, the resistance of the floor, the toilet flange bolts etc. held against the pressure until the flange bolts let go. They were only about 1/4" sheet metal screws into 1/2" plywood.
I ended up reinforcing the toilet mount by taking about a 12" square of 3/4" plywood, cutting a hole for the 3" drain pipe, cutting the drain apart, sliding the wood up underneath the bathroom floor and mounting it there with some screws. Then I went inside and drilled 1/4" holes through the flange mounting holes all the way through the floor and plywood. Then I put 1/4" x 4" bolts through and secured them underneath with fender washers and nuts. I reassembled the drain pipe with a couple of flex couplings.
I also put a clamp around the 1 1/2 " vent pipe to the side of the plywood support to give it some resistance to movement. Then I added a 1 x 2 furring strip to the edge of the storage compartment floor to stiffen it some. I screwed it into the front compartment vertical divider right at the bottom edge.
I don't know for sure if this is enough reinforcement to prevent all damage if the tank is overfilled in the future. But hopefully it will help.
I think the key thing is going to be to not overfill the tank again.............
