Won't Start

I have had several issues with starting my 1999 suburban v-8 I replaced battery which helped some- It seems the engine would not start after sitting overnight-It would crank over but not start I took it to a chevrolet dealer and they charged me $600 to change out the fuel pump located in the fuel tank--It started fine for a couple of months and then started the same problem over again-- I noticed that when I would go to start the car in the morning the voltage meter on the dash was only reading 10 volts, I hooked up a battery charger and after a couple of minutes of charging the engine would fire right up--once the engine was running the volt meter on dash would go to 14 volts which told me the altenator was charging--it is obvious that the battery is losing its surface charge --why?--I checked to see if there was a draw at battery but did'nt detect one-- I still hav'nt located real problem but feel the surface draw must be coming from the altenator when engine is off or from control module the battery I purchased was from battery plus it is now one year old and is the best battery they have for this car it cost over $200--I hate to just start buying replacement parts and guessing what the problem is but I do know I can't keep paying someone $600 and not have it fixed--anyone have ideas--if I do find the correct fix I will post--thanks