Can anyone tell me how and where the water comes into the boot?

Hi Wesley

it quite a common occurrence from what I have learnt, check the condition of the rubber seal around the boot, any splits holes etc could be the entry point, sometimes there are gaps around the lights were they sit against the bodywork 

Steve

Oh and welcome to the club

Welcome to the club, Wesley.

I had exactly the same problem and I never found our where or how.  I did put some tissues just underneath the battery to smack away any excess, and then I did what Steve has suggested.

My car had sat in a dealers storage garage for over 3  months and I guess the boot had never been opened and that the seals around the boot has been compressed.

Using a cloth sprayed with a mixture of vinegar and water I thoroughly cleaned the seals for a few times and eventually the leakage stopped.

Regards,

Peter.

I had the same ,boot rubber had cracks and holes in it, replaced the rubber and it has never leaked since

Another possible entry point, other than the seals and the lights is a small rubber grommet leading to the rear bumper,  down near your right knee as you lean into the boot.  Make sure this is in place and in good condition.