Recently, i have seen a lot of pond builds that do not use bottom drains. Also, i have seen ponds where people have installed bottom drains incorrectly. I want to make this clear to anyone who wants to build a pond. BOTTOM DRAINS ARE NEEDED. A bottom drain must be installed at the lowest point in a pond. Preferably in the center. You want to dig your pond so all the waste funnels down to the center, where the bottom drain is located. That way, waste will not accumulate at the bottom of your pond and you won't have to drain and clean out your pond. There is a reason why you don't see bottom drains in pipe sizes below 2". No matter if you have a very small pond or a very large one, the leaves are the same size. Anything smaller than 2" will trap leaves and debris. I also recommend getting a priming pot with a basket BEFORE your pump. I did not do this with my pond and debris got caught in the pump. I have one that i am going to add. Also, use AT LEAST sch 40 pvc. You can also use SCH 80 pvc. Just stay away from the SCH 20 pvc. There are retrofit bottom drains that you can add that sit at the bottom of the pond, but they are not as good as a real bottom drain. Stay away from submersible pumps. Spend the money and get a real pump like an Evolution Series pump from Advantage Manufacturing. They are good pumps at a good value. External pumps are the most efficient.