I believe that you by 'FDA' certificate means 'Food and Drug administration certificate' and most likely for US. (Please remember you are adressing a world-wide forum, with members spread out all over the globe)
Iam familiar with rules for drinking water in Europe, but not FDA. In Europe it might be necessary to prove that the valve materials (body/trim) lies within limits for not contaminating the water over time with poisonous/undesireable amounts of metal in the water, for instance lead or others. This in addition to requiring acknowledged (certified) type of wetted sealings.
In adddition to this special rules and restrictions might be required locally, or if the water is used for special purposes (loboratories, food and drug production etc.) For water purification plants where UV light or chemical components are added restrictions on materials is also likely.
The only way to be sure is to check with the local authorities and the end-user. (Generally high-quality CF8M should be OK for normal drinking water)