The goal of alum feeders is to minimize chlorine generation. They are placed on top of the filter bed and filter the surface instead of the filter depth, which results in shorter runs. The filter bed is made to filter out bugs and particulates, not as a sanitizing process. To use alum, flow rates must be reduced. On high rate sand filters, when using alum, CH developed a policy of dropping down to 13 GPM/ft2 across the filter bed. This was in hope that more particulate would be captured in the 8 to 10 micron range, rather than up around the 40 to 45 micron range where particulate is normally caught.
Alum is used to control organic loading in pools that use bromine. It is recommended by bromine manufacturers. Vantage combines bromine and ozone with alum.
When alum is used with chlorine, it doesn’t minimize chloramine generation, it actually accelerates it.
Alum should not be used with Zeolite.
Alum feeders are not required by any code and were a CH design standard in the past.
CH does not recommend the use of alum feeders and they have been removed from the master spec.
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