e90 power drain

[REVS1123]

Hi Guys
I had not used car for a approx a month and battery was totally flat. I recharged but still same issue so i bought a new one. Two days later totally dead.Left the car with my friend who is a mechanic. Previously about a year ago he replaced the water pump on this vehicle and i noticed that the water pump was running continuously when the engine was running. I asked him at the time and he said it was normal for it to do so. Now he tells me that i must replace the water pump because it is draining the battery even after switching off. Any advice regarding the above. Was the pump faulty

 

[Jakes4R]

Definitely sounds like something is drawing power in the background. Did the mechanic do a parasitic draw test? If not, first take the car to an auto electrician to perform draw tests once the car is in sleep mode. It might be a wiring or relay problem.