I plumbed a bathtub drain into mine and ran the drain line to a lower part of the yard. I was going to plumb in a valve but it would have been too close to the surface and freezing in the winter would have been an issue so I opted for a rubber stopper. I've learned a few things on this one and will do the next one differently. Next time I will rig up a 2 inch or larger drain so that all the feathers make it out. With the bathtub drain I get an occasional blockage that I have to deal with. The other thing is that these plastic ponds will float up when you drain all the water out of them so, I put about 300 lbs of large rocks in the bottom of mine. All the rocks just hold more dirt and debris. Next time I will go with 2 inch or larger drain, I will bring it up about 4 inches off the bottom of the pond, then I am going to pour concrete 4 inches deep inside of the pond, sloped towards the drain. I figure the smooth concrete surface will be much easier to clean and still provide the weight so I don't have to worry about the pond floating up if there is a lot of ground water.
