I'm in japan, water shut off , building filter.

Sorry if this is preexisting..  I'm a bit pressed for time.   I am trying to get some activated carbon to make a water filter good enough  for showers  and washing clothes.   My biggest concern here is agricultural run off.  I have a very shallow well.   my thought is to get some PVC  maybe 75 mm  ...   X   400 mm     put a narrow in and out on it...   pack it with activated carbon and sand ...    I'm curious who may have tried this??   does anyone know what  granular size the carbon should be??   can I use regular charcoal temporarily???   my understanding is that the granular size isn't  so much  important if I have enough medium for it to go through since it still has to pass over the surface.   any  ideas would help,,  I need to get this done.   I have reg charcoal now ...  I can get the activated in a few days.  oh yea,  I have a pump to feed this so my filter should run under pressure from that.

thanks

B

Poking around what we do have here, I'd be comfortable using any water that had been filtered through carbon for cleaning. There are a few interesting discussions about the qualities of ones on the market or reference basic sand filters.
This thread https://permies.com/t/25198/permaculture-home-care-cleaning/purity/Water-Filter-Systems-water-testing actually shows a simple diagram for a filter style that I think you could easily adapt for an inline system.

You might find this one interesting, even if just for the novelty. It's also an inline system, but I doubt it could handle much volume. https://permies.com/t/33567/permaculture-home-care-cleaning/purity/Simple-Pine-Branches-Filter-Bacteria

edit: fixed link

Hi Brendan,

I'm low on experience in this area, but have stumbled across the biosand filter a number of times when exploring similar questions. Here are two links that may be of use:

https://www.sswm.info/sswm-university-course/module-6-disaster-situations-planning-and-preparedness/further-resources-0/biosand-filter
https://www.biosandfilters.info/
https://purewaterfortheworld.org/2017/04/12/how-does-a-biosand-filter-work/

My understanding is that the grain size is crucial for proper filtration. Also, they will deal with bacteria - not with agrichemicals, so it depends on what you are trying to filter out. Charcoal would probably be better for the chemical removal, which you're looking at doing anyway. Hope you get it sorted out effectively.