I just built a used Doughboy AGP in my back yard. Yesterday I managed to get the skimmer and return cut into the liner and I hooked up the pump and sand filter. The sand filter is older, I would say it's from the mid to late 90's. It's a Hayward, but I forgot to check the exact model (it holds 130 lbs. of sand and the valve in on the top). The main body of the filter is two halves, top and bottom, that are joined at a flange with roughly 20 nuts and bolts. This seam is leaking like crazy! I tried making the bolts tighter, it doesn't seem to help. Do I need to replace the O-ring inside of the flange? Is there some sealant I should have put on the o-ring?