I'm just wondering if anyone has had good results using filtered rain water instead of distilled water for things like mixing with film developer (e.g. Adox Adotech) and final film washing? What size micron filter would be needed to remove visible/effective impurities - 5um, 0.5um?

Our water supply is rainwater so I was thinking it'd be a cheap, on-tap (literally) supply. We don't filter it for our consumption but I was thinking I could make a buy a filter for chemical mixing.