Waste tank expansion (movement) on top side

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.