I have a crack inside the skimmer wall. The previous owner repaired the crack, I can see white putty like material along the crack line. The skimmer is leaking now again. I searched the board and found out that I can repair the crack with 2-part epoxy. My question is that how do I figure out if the previous owner used 2-part epoxy. If so, do I need to get the old epoxy cleaned up before applying new epoxy? Can I just sand off a thin layer of the old epoxy. Does epoxy bond well with old epoxy? I will take pictures once I get home. Thanks.