Existing human drinking water standards (pH 6.5-8.5) were established decades ago for aesthetic reasons (especially taste) and to protect plumbing from corrosion, rather than upon health-based criteria.392,408 Although a number of Cooperative Extension Service Web sites suggest water below this range will produce pathologic acidosis in cattle, none we examined offered hard evidence. Nor were we able to find any references to direct health effects of moderately acidic or basic water in animals. There are a number of references to the beneficial effects of acidifying laboratory animal and swine water with mineral acids to pH 3. The only adverse effects in these reports were relatively subtle and occurred at pH < 3.0. The only example of feeding a pure mineral acid to ruminants (equivalent to approximately pH 2-3) resulted in acidified urine, but there were no adverse health effects over a several week period. There is no equivalent data 33 for basic drinking water. From a purely pathophysiological standpoint, it seems unlikely that water with a pH between 3.0 and 7.0 would cause health problems in otherwise normally managed animals. An exception might be feedlot ruminants, which are often marginally acidotic as a metabolic consequence of the high soluble carbohydrate rations they receive. In this case, acid water might be sufficient to trigger a crisis.
The other potential adverse effects of basic or acidic water involve mobilization of potentially toxic substances (e.g. metals) from plumbing or soils. While it seems unlikely the amounts mobilized would be sufficient to actually cause poisoning under most conditions, it is quite probable they would be large enough to cause water refusal. Because the effect of any given pH on palatability depends upon what the water contacts, there is no way to make any wide-reaching recommendation in this regard.
We suspect the commonly touted acceptable ranges for drinking water pH (a low of 5.5-6.5 and a high of 7.5-9.0) are excessively conservative from a strictly animal health standpoint, at least on the acid side, but there are not sufficient experimental and/or clinical data to offer a specific alternative.