2012 Landmark Rushmore ,105 gal tank?

I've been having trouble with my fresh water capacity. It doesn't seem like it is taking on 105 gallons of water so I drained it and filled it with an in line water meter. The over flo tubes spill at 75 +- gallons.
So has anyone else ever had this happen?
Do you think it's possible for the tank to become misshapen/ collapsed?
No sign of leaking.
Thank you

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Carl,

If your 2012 has the gravity fill, as does my 2011, the vent tube can spit out water way before the tank is full. And yes, tanks can change shape. Usually, they sag. But I have seen at least one that was grossly deformed and partially collapsed. No idea how it happened.

The inexpensive inline water meters, per past discussions, may not be as accurate as you might hope, so was it really 75? Maybe.

Dane,
The tank fill is through the new brass Anderson valve. And your correct about the accuracy of the water meter.
I'm in Nashville Tennessee and plan on peeking at the tank when I return to Florida.
I can fill a 5 gallon pail to verify the accuracy of the meter.+-

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