Some places with weird water profiles will set up RO systems and add minerals to build a water profile on top of that, but it's far from the norm. People decide based on how their municipal water supply works with the kind of beers they want to make. I've seen a few brewhouses in the process of being built and talked to some commercial brewers about water, and depending on the location some places just use municipal water. New York water has a great profile for beer.

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timr 11 hours ago | parent [-]

You don't need reverse osmosis to filter out PFAS -- activated carbon will do it.

	▲	d4v3 11 hours ago \| parent \| next [-]
		Activated carbon will remove the larger chain PFAs, but is not as effective as removing the smaller ones. From the paper: > Conventional water treatment employed at municipal drinking water treatment plants have been shown to be nearly ineffective at removing PFAS. This can leave the burden and cost of implementing more sophisticated water treatments to brewers unless public water suppliers implement tertiary treatment to remove PFAS from finished water prior to distribution. Anion exchange and activated carbon treatments have been shown to more effectively remove longer-chain PFAS and PFSAs but were less effective in removing PFCAS and the alternative shorter-chain PFAS and PFECAs. Reverse osmosis treatment showed significant removal of PFAS of different chain lengths in drinking water, but can be prohibitive due to high operational costs and energy usage. In areas with known contamination, beers from macro- breweries were less likely to have detectable PFAS than craft beers brewed at a smaller scale, potentially due to more effective and expensive filtration of tap water at larger breweries.
	▲	ch4s3 10 hours ago \| parent \| prev [-]
		This isn't correct in the general case. In the specific case of brewing, if you're filtering at all it makes sense to use an RO system so that you can then do mineral adjustments from the RO base water.I'm not aware of any brewers outside of homebrewing using charcoal filtration.