Tank vents

My brother-in-law's Adams 40 has water tanks (FRP.....) located under that saloon setees. They don't have any breathers, so as water is (attempted) pumped out, it pulls a vacuum! He can install simple vents that would run up inside the cabin, finishing just below the cabin / deck 'joint'. Is this going to be high enough? Running them any further up would mean that the vent tubes would be in sight, inside the cabin..... see rather simple attached

Also, his only fuel is a bladder. He intends to install a permanent tank and use the bladder as emergency fuel. Where should the new tank's vent go?

 

From where are you filling the tank, inside or outside, in case of the later you run the risk of flooding the boat while filling the tank!
Also check the hight of the breather when the boat is heeled. If that checks out it's not a real problem.

For the fuel tank, the vent has to go outside!! Can it be run up inside the mast? Or loop it, underdeck to the centerline, and then back to just above the waterline.

 

Thanks Dutch
Yes, the heeled condition was our concern - though the boat would almost need to be in a roll-over state before any water could come out...

And yes- of course the fuel vent needs to be outside. I was thinking of putting the vent on the transom - I'll give the loop some further consideration, but no, I don't think it could go up the mast...