It could be one of two drains (that I can think of). Either your water heater pressure relief valve or air conditioner drain line. Usually the A/C line is close to the condenser. (if your not in A/C cool mode yet it’s prob your pressure relief valve). Is the water comming out hot? If so, you need to have a plumber come change the valve. It’s wasting water and energy. If it’s cold it prob your A/C, this in normal.