A bottom drain is basically a drain at the bottom of your pond that sucks in water.
That’s it. That’s all it does.
It’s a little bit like a toilet in how it works. It has a pipe that goes up to a valve called a “ball valve” that keeps water from flowing back out. It’s the same kind of valve that you have in the bottom of your toilet tank.
The water then flows out of that pipe and into your filter system, where it’s cleaned before it’s pumped back up to your waterfall or your fountain or whatever.
The only other thing you need to know is that there’s a flexible pipe that you’ll need to connect to your bottom drain so that you can connect it to your filter system. You’ll need to dig an underground trench for that pipe to lie in.
The pipe also has to be slightly sloped downwards towards your pond’s filter system. Otherwise, water will just sit in the pipe and not flow into your filter system. The slope of the pipe should be about 1 inch for every 10 feet.
Don’t worry about this too much, though. You can always adjust it later if you find that your pipe is too horizontal and not steep enough.
What Size Bottom Drain to Get
The size of your bottom drain depends on two things:
- how big your pond is
- how many fish you have
The general rule is to get a bottom drain that can handle 4,000 GPH (gallons per hour) for every 100 square feet of pond surface area if you have a few fish, or if you don’t have any fish at all.
If you have fish, then you’ll need a bottom drain that can handle 6,000 GPH for every 100 square feet of pond surface area.
Why?
Well, the first thing you need to know is that you should cycle the water in your pond at least once every 2 hours. Anything less than that is bad for your fish and bad for the health of your pond in general.
The second thing you need to know is that your bottom drain will be the main thing that cycles the water in your pond. That’s why you’ll need a bottom drain that can handle a certain GPH of water.
“4,000 GPH for every 100 square feet of pond surface area” is the minimum amount of water cycling you can get away with having. Anything less than that is just asking for green water and other kinds of pond related health issues.
If you want to be on the safe side, then you should get a bottom drain that can handle 6,000 GPH for every 100 square feet of pond surface area, even if you don’t have any fish.
Again, that’s because your bottom drain is the main thing that cycles the water in your pond. The more water it can cycle, the better.
