Yes, I use zeobest and I like it. Its more expensive than sand, of course, but well worth it. Easily rechargeable.http://www.zeobest.com/CD.html
Sounds like your master control valve O-ring is leaking. Or worse, there was water in your valve over the winter, and it froze and cracked your valve. Dissassemble it to find out. If you just need to replace the O-ring, don't forget to get some of the O-Ring silicon gel to put on it. Your local pool-supply store should have it in stock, or you can find many online stores that sell it.