The pool is 16 years old. The previous owner of the house was there only one year and did not know the history of the pool. The pump suction has one return from the spa and one from the pool. Only one return from the pool, as opposed to one return from the pool drain and one from the two pool skimmers. The inside of the skimmers have some lettering that leads me to believe there was some mechanism to partially close off the skimmer and draw more water from the drain. If I set the pump suction to draw from the pool and not the spa, and then I plug off the skimmers, the pump loses pressure (0 psi). To me that means the drain is clogged. It may be a deliberate modification. Maybe the skimmer flow restricters became obsolete. When I sweep the pool, the drain does not seem to suck the cloud of debris pushed to the bottom.
Are there service providers that could check out the drain and line without having to drain the pool?