Here is the problem that I am having. When I close off the main drain the suction at the pump decreases only slightly (but is still adequate). Once I install my Hayward automatic vacuum into the skimmer line, the pump starts sucking air and the water flow in the pump basket drops dramatically. I just replaced the valves and plumbing at the pump. I have also checked the vacuum and the vacuum hoses for cracks or obstructions and found neither. I have the regulator attached to the hose and installed it correctly into the skimmer line. I performed a dye test with the equipment off by putting a couple of drops of dye in front of the skimmer. The dye did not flow into or down the skimmer. The dye ultimately started sinking to the bottom of the pool. I have not had to add water to the pool, nor have I discovered dirt or sand in the filter. A pool service told me that I have a break in the skimmer line and wanted to charge $250 to locate it after they charged me $180 for new valves and pluming at the pump which did not fix the problem. Any suggestions on what might be causing this?

If it were mine I would try to bypass the skimmer line. Cut the skimmer line at the pump and hook up the vac there. If it works the problem is in the line. It does not fix the problem or locate the leak but you will be sure there is a leak in the skimmer line. When you are done reglue the PVC pipes back together with a couple of couplings as it was before.

The only for sure way to tell is to pressure test the skimmer line. This is a quick test and should not cost much to have a leak detection company do this for you. They can also pinpoint the leak down to a small area so you don't have to dig up the entire pipe.