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 flush and turned it on.... Was sitting out side when we heard a "POP" and got splashed, then water started running of the roof.....Well, shut off the water and started investigating. Figured out I hooked up to the flush and overfilled the black tank. Drained the tank and started looking for damage. No sewage inside. But, the vent pipe and toilet moved upward with enough force to rip the toilet mounting screws out of the floor.I decided to refill the tank from the toilet and check for leaks. Found no leaks. But as the tank got very close to full, somehow it flexes suddenly and lifts the toilet and vent pipe. The vent pipe moves upward about 3 inches..... Toilet not as much.Would have been no damage except for the tank flexing. It seems really odd to me that the top of the tank would move that way and with so much force.I am think of cutting the drain pipes apart inside the storage area and reassembling with flexible couplings to allow some movement so future potential flexing doesn't rip the toilet off the floor and ruin the vent pipe seal on the roof.Have any of you ever heard of such a thing?

The integrity of that tank has been compromised.Instead of bandaid fix (flexible couplings) which will just create even more problems...........replace tank, redo toilet floor flange (new screw locations, bracing for toilet base etc)Do the repairs correct the first time.Water going into tank faster than vent line could expel the air caused the pressurization of tank. That was a lot of sudden force when tank POPPED as evidenced by displacement of toilet and vent line

Thanks for the thought.I am planning on bracing and re-securing the toilet by using wood underneath the floor and running bolts all the way through the flange with nuts and washers. But, I was thinking the flex couplings would help prevent transferring the tank movement force to the flange in the future. The piping is not a straight through affair. There are 2 45 degree fittings creating on off-set drop which is where I should be able to allow a little flex.I don't think the tank had any more pressure exerted on it other than the weight of the water.How can a 5/8" hose going to probably a 3/8" inlet line to the tank flush let water in the tank faster then a 1-1/2" vent line let air out?The 2nd time the tank moved, the toilet valve was wide open. It seems to me when it gets a certain amount of weight, it suddenly flexes in a manner that causes the top of the tank to move.Another thing I found odd was, in the past I called the manufacturer about the grey tank leaking when overfilled and I was told they use a soft connection at the top of the tank to allow movement and flexing to happen without breaking things. But now I find nothing but hard pipe glued solidly between the toilet and black tank.

Larryect wrote:Thanks for the thought.I am planning on bracing and re-securing the toilet by using wood underneath the floor and running bolts all the way through the flange with nuts and washers. But, I was thinking the flex couplings would help prevent transferring the tank movement force to the flange in the future. The piping is not a straight through affair. There are 2 45 degree fittings creating on off-set drop which is where I should be able to allow a little flex.I don't think the tank had any more pressure exerted on it other than the weight of the water.How can a 5/8" hose going to probably a 3/8" inlet line to the tank flush let water in the tank faster then a 1-1/2" vent line let air out?The 2nd time the tank moved, the toilet valve was wide open. It seems to me when it gets a certain amount of weight, it suddenly flexes in a manner that causes the top of the tank to move.Another thing I found odd was, in the past I called the manufacturer about the grey tank leaking when overfilled and I was told they use a soft connection at the top of the tank to allow movement and flexing to happen without breaking things. But now I find nothing but hard pipe glued solidly between the toilet and black tank.Tank movement is upward.that is not from weight of waterWater going into tank is under pressure...at how many gallons a minute???Soft connection on tank is by using a grommet at top of tank where line connects to tank. Line slips thru grommet into tank. Grommet seals tank opening and allows for minor movement..........not over-pressurizing of tank as witnessed by toilet ripping away from floor and blowing out top of vent line creating a poop shower.

Don't know the GPM. But, the second time we were filling through the toilet water valve, only, with the toilet flush valve open - allowing no pressure build up, when the tank again suddenly moved again knocking my foot off the valve. It was like something flexed sudden like. Not a slow pressure build up. But with the 3 inch flush valve open watching water flow into the drain there is no way there could be pressure.

I am thinking there is some odd wrinkle in the tank that changes due to the weight of the water.Possibly I should open the bottom of the trailer so I can see better what is going on.......

Waste tank expansion (movement) on top side | Good Sam Community

16 Replies

Larryect
Explorer
Jun 16, 2015
There would have been some pressure the first time - whatever it takes to force the water up the vent pipe at least....
Larryect
Explorer
Jun 16, 2015
I am thinking there is some odd wrinkle in the tank that changes due to the weight of the water.

Possibly I should open the bottom of the trailer so I can see better what is going on.......
Larryect
Explorer
Jun 16, 2015
Don't know the GPM. But, the second time we were filling through the toilet water valve, only, with the toilet flush valve open - allowing no pressure build up, when the tank again suddenly moved again knocking my foot off the valve. It was like something flexed sudden like. Not a slow pressure build up. But with the 3 inch flush valve open watching water flow into the drain there is no way there could be pressure.
Old-Biscuit
Explorer III
Jun 16, 2015
Larryect wrote:
Thanks for the thought.

I am planning on bracing and re-securing the toilet by using wood underneath the floor and running bolts all the way through the flange with nuts and washers. But, I was thinking the flex couplings would help prevent transferring the tank movement force to the flange in the future. The piping is not a straight through affair. There are 2 45 degree fittings creating on off-set drop which is where I should be able to allow a little flex.

I don't think the tank had any more pressure exerted on it other than the weight of the water.

How can a 5/8" hose going to probably a 3/8" inlet line to the tank flush let water in the tank faster then a 1-1/2" vent line let air out?

The 2nd time the tank moved, the toilet valve was wide open. It seems to me when it gets a certain amount of weight, it suddenly flexes in a manner that causes the top of the tank to move.

Another thing I found odd was, in the past I called the manufacturer about the grey tank leaking when overfilled and I was told they use a soft connection at the top of the tank to allow movement and flexing to happen without breaking things. But now I find nothing but hard pipe glued solidly between the toilet and black tank.

Tank movement is upward.that is not from weight of water

Water going into tank is under pressure...at how many gallons a minute???

Soft connection on tank is by using a grommet at top of tank where line connects to tank. Line slips thru grommet into tank. Grommet seals tank opening and allows for minor movement..........not over-pressurizing of tank as witnessed by toilet ripping away from floor and blowing out top of vent line creating a poop shower.
Larryect
Explorer
Jun 16, 2015
Thanks for the thought.

I am planning on bracing and re-securing the toilet by using wood underneath the floor and running bolts all the way through the flange with nuts and washers. But, I was thinking the flex couplings would help prevent transferring the tank movement force to the flange in the future. The piping is not a straight through affair. There are 2 45 degree fittings creating on off-set drop which is where I should be able to allow a little flex.

I don't think the tank had any more pressure exerted on it other than the weight of the water.

How can a 5/8" hose going to probably a 3/8" inlet line to the tank flush let water in the tank faster then a 1-1/2" vent line let air out?

The 2nd time the tank moved, the toilet valve was wide open. It seems to me when it gets a certain amount of weight, it suddenly flexes in a manner that causes the top of the tank to move.

Another thing I found odd was, in the past I called the manufacturer about the grey tank leaking when overfilled and I was told they use a soft connection at the top of the tank to allow movement and flexing to happen without breaking things. But now I find nothing but hard pipe glued solidly between the toilet and black tank.
Old-Biscuit
Explorer III
Jun 16, 2015
The integrity of that tank has been compromised.

Instead of bandaid fix (flexible couplings) which will just create even more problems...........replace tank, redo toilet floor flange (new screw locations, bracing for toilet base etc)

Do the repairs correct the first time.

Water going into tank faster than vent line could expel the air caused the pressurization of tank. That was a lot of sudden force when tank POPPED as evidenced by displacement of toilet and vent line

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Waste tank expansion (movement) on top side

16 Replies

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