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Does your father have any medical history. Any prostrate problem. Since when is he having this excess urination. Any fever
and abdominal pain
as well. It could be prostrate enlargement which is causing urinary infection which is making him pass more urine, considering his age. It would be best to consult Urologist
and do urine test as well and get his problem assessed and treated. Let him drink 6-8 glasses of water if he has no cardiac or renal problem.