A friend had a small flood from getting side tracked during a water change. It reminded me of my solution to this. These work with a standard garden hose, and will clamp onto the side of a tank. When the water reaches about an inch or two from the top it will shut the water off. If you have a hood, or a wall around the top, you may need to be creative. These work, and we use them for cattle, goat, chicken and turkey water troughs. You can do a water change, start refilling and walk away. A couple hours later when you come back, your water will have stopped flowing and your tank will be topped off. After a few floods in my unfinished basement, I started using these. A 30% water change on a 240 takes a while, so instead of watching a tank fill I would mow the lawn or something. Occasionally I would forget and come into a flooded basement. Once even forgot, and slept on it. Next morning, very flooded basement, and fish looking terrible from chlorine. Dumped a bunch of dechlor in and a bunch of vitamin C and think I might have lost one fish.
Anyway, with a float valve, you can start a refill and walk away with confidence that you will not cause a flood. For 10 bucks it is a no brainer. May not be worth it for anyone with small tanks, but for those of you with bigger tanks that have seemingly unending water changes, they are worth their weight in gold.
This is a very basic model that works fine for us in water troughs for a couple years of constant use. For changing water, it may last a lifetime.
http://www.tractorsu...tic-float-valve
Don't leave it unsupervised your first time. Make sure the level is adjusted correctly. After that, have confidence. Make sure you use a good hose, as when the valve shuts off water flow, your hose will have about 40 psi in it. So don't blame me if your cheap worn out hose blows.
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