Senior officials from the semi-state company told the Department of the Environment two years ago that it was not necessary to install water meters before charging people for water.
During an interview with Midwest Radio, Mr Kenny said: "It's not true to say water meters are not required."
The Taoiseach said meters were needed to detect leaks and encourage water conservation.
He also insisted the new revised water charges are "very affordable" and questioned the motives behind those protesting against meter installations.
"What you saw on the streets in some cases has little to do with Irish Water, or little to do with water or little to do with contributions," he said.
"I think you can read between the lines yourself," he added. Michael McNicholas, chief executive of Ervia - Irish Water's parent company - said he believed the water metering programme would pay for itself.
Separately, Mr Kenny addressed suggestions Nama was considering paying developers bonuses for meeting financial targets.
"I don't support bonuses in any shape or form for this sort of thing, I've made that clear to Nama," he said. He added: "In these times when confidence is coming back, it is in my view much too early to consider bonuses like that."
Nama have denied they will pay developers bonuses but said it was considering "incentivisation arrangements" in a small number of cases.
Mr Kenny said the Government would address the issue with Nama through the Department of Finance.