Ideas for a Large top up Reservoir

[Todd]

I am going to be gone for a week next week, and may be gone for alot longer then that in August / September. My tank does well by itself as the lighting is timed, and I don't dose daily as well everyone eats flake so having a auto feeder does the trick for a short while.

The problem is that with 2 x 400w of lighting and the warmer temperatures I go though alot of top up water. I am currently using a gravity fed top up with a 5g reservoir on a float valve in my sump. But as I am going though 2-4 g a day I am going to need something alot bigger then that. Does anyone have any ideas?

I was thinking of taking a Rubbermaid and installing a waterline connector on the bottom - has anyone tried this? It would be nice to have something that fit under my stand and over the sump as the 5g does, but I haven't been able to find anything quite right. I looked at some water tanks at Industrial Plastics that would work well, but they are much too expensive (Start at around $100). My tank is too far for me to run a line from my RO / DI unit as well.