Polaris Scientific Ultraviolet Water UV System Ballast, 24W - 39W 110V/220V

Not too bad of a price. Almost always available. Low failure rate.

Don't ask me how I broke my last ballast...ok I'll tell you. See what had happened was, I was moving some tools around my well house. The well house is where I keep my pump, water filtration and large tools. Well, being the hoarder that I am, I had way too much stuff in there. My wife keeps telling to get rid of stuff, but what if I need it someday? Anywho, I was moving my rototiller out so I can til up the soil by the barn, but the cord for my UV light got caught and when I yanked the tiller out, stupid ballast came crashing down and it shattered. That's why I am buying a new one.

This is very reliable. I haven't had an issue with it. It's always on and you'd think that it would burn out. Nope, it keeps on working.