battery gets drained on chevy why?

Have the battery and alternator tested. Even thought they are new (or rebuilt) they have been known to be bad. Then check to make sure there is not a light that stays on when everything is supposed to be off (ie glove compartment light, dome light, trunk light, engine compartment light).

I know that my second gen Camaro would lose charge over a week - between the newer stereo and the clock assembly, I seemed to have quite a bit of draw. If you have an aftermarket stereo with an amp, check the connections from it to the fuse panel and be sure the amp isn't connected to that fuse - the clock/lighter fuse is obviously not ignition switched, which would mean your amp is continuously on. Another thing you might have is that you could have a short or burned bulb/switch on your courtesy circuit - for example, if your courtesy light doesn't work, it could very well be because the line routed to it has grounded, causing a significant and slow drain (not to mention a fire hazard!). Unfortunately this means chasing a possible gremlin in that circuit, which is a major pain - but that's where I'd probably start looking - at any possible spots where the interior lighting circuit may be causing problems (light sockets, door switches, lighter socket circuit). I don't want to sound like I'm busting your chops, but did you make sure the doors were closed when you checked that circuit? Obviously if the dome light was on, you would see a current load, and suddenly a current drop, on the multimeter when you pulled the fuse for that circuit. I only ask because I'd be likely to do that, in my frustration in chasing down a problem!

There is a flaw in the connection between the alternator and the battery. The battery is not charging. Because it is new, it recovers on its own but soon, it won't and a new battery will be a dead battery.

It may be simple or mechanical. You need to take it for a diagnostic evaluation by someone who knows cars.

Something could also be busted causing a light to stay on (for examble in the glove compartment) thus draining the battery overnight. This actually happened to be so you may want to inspect the vehicle at night once you get a good charge on the battery.

after jump start did you go have it check to see why it was dead first time

most any shop or parts store wil check charging system most do it for free and it only takes a minute or two dont have to guess at what it might be jump start it again go hav eit check to really know for sure

most likey just a battery but could be one of four or five things as well have it check best choice

You have a short somewhere you might consider putting a switch in that cuts power to the battery

It can be the connections on the terminals are loose, or the negative terminal isn't grounded well to the chasis. Usually the negative ground terminal is bolted on to the chasis(body), try to clean the connection and make sure the bolt is on tight. If that wasn't the cause, at least it's ruled out.

either bad new battery or bad new alternator. Battery either won't hold the charge or the alternator isn't charging the battery.

First question - Is the battery getting charged.

2nd - Is the starter faulty.