ge tfx20jr leaks water when filling icemaker?

Hello and Thank you all in advance, I placed an inline filter on my friends side by side, and then turned on the water flow, he hasnt used the Icemaker or Water thru the door or turned the valve on since he had no filter system for it, that was since 1996...so in my good deed of course, everything was tight and dry, as it should be, untill when I dropped the lever on the icemaker unit, water flowed, and the flow thru the door to the dispencer is fine... a while later I noticed water on the floor, cold water, and as I was mopping frantically, opened the freezer door, some water flowed out, drain clogged from disuse, when I opened the refrigerator door, that is when approx a gallon or so of cold water dumped on the floor. Copper supply line, when you dispence water you can hear it flow, I am asking for any and all info, so I dont rip and tear and my punishment for doing a good deed really begins...!