only those with first hand knowledge of patient can tell if enough water.
he may also be getting water when meds are administered via tube.
most common homecare order i see is 60-80 cc water tid + formula ranges from 4-6 cans/day depending on type forumula, patient wt, underlying illness + lab work so your in the ballpark. please discuss concerns with nurse.
we can not offer individual patient advice per terms of service