I am building a 1 acre pond that will be lined with a liner. I want to be able to drain the top 2 feet off of the pond and use the water to help supplement irrigation on a 5 acre alf alfa field that is down 5' from my pond's water level. My plan is to have a 12" pipe perforate the liner about 2' feet below the water surface, travel about 10' feet and then have a valve of some sort, and then travel the remaining 100' feet to the alf alfa field. My question is what sort of valve should I get? I would like to get one that doesn't leek and that will last for many years with usage once every week or two. I am looking to get this in place this week so any help would be appreciated. Thanks!