by Steve on Tue Jan 29, 2008 4:59 am
Hi Sara,
There are a few threads about bottom drains under the Projects topic in the forum. You will find some on this forum have bottom drains and others don't. I find the bottom drain to be important and wouldn't consider running a pond without one. But they can also present problems.
The main function of the bottom drain is to take the heavier 'dead' water and debris from the bottom of the pond to a seperate chamber, where it is either passed through the filtration system or discharged into the main drainage system (e.g. standpipe system). Though I don't have a conventional type of bottom drain, it functions in the same way. Our bottom drain connects back to the input to a solids seperator. The solids seperator then connects to a bead filter and the output of the bead filter is piped back into the pond.
The addition of the bottom drain helps reduce the amount of vacuuming of the pond.
To be really effective, it is essential to scallop the bottom of the pond and position the drain(s) in the center of these dished area(s). This way all the debris will flow toward the drain. Areas of the pond bottom that are flat are places where debris can accumulate 'dead spots'.
If you install more than one drain it is recommended each drain have a common pipe back to the drainage system or filter. If you connect two drains to a common outlet, remember that the pull suction will be halved. Also, if a clog should occur in the common part of the pipe, then both drains would fail.
There are many types of bottom drains available on the market. Some good, some not so good. What may be good for someone may not be so good for someone else. There are manufactures that make retrofit bottom drains for existing ponds. Haven't heard if these are any good or not. In our original pond we had a Tetra bottom drain. The drain contained a plastic dome that helped prevent the Koi from getting sucked in. For us this seemed to work, but we had problems of frogs squeezing under the dome and getting sucked in. Most of them I found at the other end. But every now and then one would get clogged and what a pain it was to get it out. Another issue I had was that the check valve failed (used to keep the pump primed) and it was located under the pond, thus making it impossible to service.
Last year we completed a pond expansion and decided to create a custom bottom drain. I wanted something that was easy to service. All the piping actaully resides in the pond itself, not underneath it. Further details of it can be found in the Projects topic section. I've been very happy with how it works. It collects much of the debris and never seems to clog. I can easily remove the whole systme should I need to. The check valve is easily accessible should it require service. Also no cutting of the liner. In the winter I disconnect the unit (I don't run my pumps in the winter), blow out the lines and capped the open ended pipes.
Again, check out the information on bottom drains that were posted in the Projects section. Some good discussions were posted.
Hope this helps.
Steve
