Question
Mark-

I just had surface drains installed in my property (catch basins with drain pipes that run to the bottom of my property).  The catch basins collect some water (a few inches) on the bottom that don't drain - the drain pipes are connected to the basin about 3" above the bottom of the basin.  The collected water attracts mosquitos and smells.  Did I poorly design the drain system?  Should I have an escape for the water at the bottom of the basins?

Answer
Hello,

A catch basin insert (I do not know if they are made for residential basins) may work but it also may fail because it may clog with sediment and debri. These filters are made of non-woven plastic geotextile filter fabric.

You could also try mosquito "dunks". These are solid chemical or organic discs. Bleach can also be used to kill mosquitos but you would have to apply bleach more frequently than discs,perhaps every few days. The discs will last about 30 days in a rain barrel and so should last longer in a catch basin.

I do not think a drain in the bottom of the catch basin would be practical. The space at the bottom of the basin is called the sump. This space is intended to settle out particles before they reach the outlet pipe.   

Flush out the basins with a hose every couple of weeks for the odor. There are also various chemical products for such odor problems or perhaps a drop or two of bleach would do the trick.

Judging by what you have told me,your catch basins appear to be designed correctly. It is normal for water to sit in the bottom of the basins and mosquitos in catch basins are a common problem. An outlet pipe connected to the bottom of the basin will not work because the pipe would then become clogged with sediment and a filter will not work because that would trap sediment and debri in the basin. Filter fabric is very problematic in catch basins. This is the reason for the sump at the bottom of the basins and hence the standing water. The sump is the only way to stop the sediment from entering the outlet pipe but the trade off is the problem of standing water and mosquitos.  Good luck. Let me know if I can be of further help.

Mark  Harshman
http://www.mahdrafting.com
Email: [email protected]

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