Fresh water tank filling problem

[osbeck]

I cannot seem to get more than 30 gallons in my 100 gallon tank. I have tried filling it slowly and quickly same result. Pump works fine no leaks in tank or lines. I know I am not filling the tank fully because I am out of water long before the black and gray tanks are full. Level reads about 1 third full. I know they are not very accurate but based upon water use I think it is about right.

I do notice that nothing comes out of the small overflow hole next to the fill hole and the water backs up and sprays back which makes us think the tank is full but again we only get about 30 gallons of usage.

Any Ideas or solutions would be welcome.
We have a Damon 1997 352 Class A 34 feet.

[JMonroe]

I'd be checking the vent line. Maybe it somehow got clogged (critters?) or kinked?

[osbeck]

We found the problem. I was a blocked vent tube. Muddaubbers had made a nest in the vent tube. Put a wirehanger down it and let the water flow. Yeah!!