I am putting in them on flat surfaces of the tank. One location is
very close to curved surfaces though. I was going to put one on the
very bottom of the tank, but these tanks will be sitting in the ground
and I was worried about getting to the seal if it were to leak. I
took pictures along the way of cutting my holes in the tanks (scary!)
and hope to post them on a website sometime. I bought some aquarium
silicon last night and am thinking about using it.
Oingofan

On Tue, 15 Apr 2003 02:25:48 GMT, GD wrote:

One thing to consider: 4" bulkhead fittings are pretty large, and may
not conform well with any curves built into the stock tanks---a "flat"
rubber seal will not take to a curved surface, no matter how correctly
they are installed. Silicone may help, but usually wears out after a
time when exposed to the elements. I suggest you rethink the bulkhead
fitting size, unless you have a flat surface available on the tank in
excess of the seal diameter.