Water Leak Fix ??

[imi-7]

I have a water leak around the water leak/ water pump area (behind alternator). I am topping up 1 litre approx every 3-4 days in the radiator. Engine runs fine, temp is normal, and coolant levels seem OK. I reckon it may be the pump or the housing. Question: how expensive/easy is it to fix something like this ?

 

Cheers

 

PS Car is a NA Auto.