We are on spring water, don't know where it originates, but old pipe to a brick storage tank which feeds the house by gravity. We don't have to have it tested and never have. Though a friend on spring water was telling me a visitor was ill after drinking her (my friends) spring water, my friend had built up a resistance to the bugs so was OK with it.
last year we put a UV filteration system in, but we've been OK for years.
Is it possible to just use the well water for garden, animals, washing and flushing loo etc? Have another header tank for that and just use mains for drinking water and if well water gets low and muddy?