Who is liable in this case?

On August 1st of this year, I turned on my shower and it leaked into the condo below mine.At first the shower wouldn't turn off. I never use it, so I didn't know why it was doing that. At the time I thought I was liable because of the shower, but it turns out that the pipe was cracked and that's why it was leaking. So the problem is in the space between my floor and their ceiling. I don't know how much a condo lawyer costs, but the damage was about $3,400 for plumbing and about $4,300 for damages. The HOA says I'm liable. Not sure what to do. A lawyer is contacting me saying she will turn it over for judgment if I don't pay. I have a very good credit rating (786) that I don't want to ruin it.