Changing bulkheads with water in tank

[LazyD]

Hey all, this is probably a pretty stupid question and I feel stupid for even asking, my 85 bowfront has 2 bulkheads in the bottom of the tank, 1 at each end, currently, the one on the left is the overflow intake and the one on the right is the return I would like to change it so both of the bulkheads are returns and use an exterior weir/overflow box for the intake. Now, the intake currently has some flexible....I dont know what it is, hot tub tube I guess you could call it. Since I want to plumb both returns to my mag 9.5 I need to change the intake bulkhead so I can get PVC fittings on there, is there anyway, short of draining my tank to unscrew and replace a bulkhead, like I said, stupid, isnt it.

 

[nyvp]

if you can find a round tube wide enough to get your hand in and high enough that it touchs the bottom of the tank and sticks out of the water you can do it.

 

[beaniebeagle]

but use something like plumbers putty (or whatever may be nontoxic, i have no idea about the plumbers putty) between the bottom of the tube and tank bottom to make a seal

 

[Zaphod]

good luck have plenty of buckets ready for when it all goes down the tube literally and figuratively. I wouldn't risk it.

 

[LazyD]

Yea, I will most likely drain it, I was just wondering if anyone had any brilliant ideas, I really do like the ideas nyvp and beanie gave me, if I was feeling brave I would give it a go