More information. This is very important. The two most recently set up slow sand filters in operation here have some important lessons to be considered. In extreme cases, a diverter by itself, will not be enough of a pre-filter:
Turbid water from a roof (or anywhere) will clog a slow sand filter within hours. Excessively turbid water comes from roofs when there are lots of trees directly above or within 20 or 30 feet of the roof surface; or when wildlife has access to the roof surface, or both. This turbidity will cause severe problems with the filter. Cleaning will be necessary to the point of preventing the filter from producing purified water. A pre-filtering system is absolutely necessary. Either a dual sand filter system (filters in series) with very coarse sand (.85 mm effective size) in the pre-filter; or an effective screen system to keep fine debris and mud-like substance our of the filter input, or both will be required or the filter will not function and will produce un-usable water. The cleaning will be required so often just to enable throughput that the output water will not be purified. This problem has occurred here with 2 of the filters that are handling roof water with only a diverter as a pre-filter.
The oldest filter here works well with 2 settling barrels acting as pre-fiters following the diverter. This filter has been working flawlessly for 6 years now. Two other filters here processing water from a surface well have been working for 3 years. In both these situations the input water has very low turbidity.