J/30 Class Association Forums J/30 Forum One Design Class Rules Bladder Type Holding Tank

I think your dimension estimates are on the large side, but don't have better data to support that without actual measurements. I do know there is no way the holding tank is larger than the potable water tank, which on Rhapsody is 18 Gallons.

Other Data to support the Tank Capacity:
Hull #371 - 14 Gallon Holding Tank
Hull #512 - 10 Gallon Holding Tank
Hull #80 - 12 Gallon Holding Tank
Hull #444 - 10 Gallon Holding Tank

I'll throw in an extra gallon on the largest shown just for you and call it an even 15....