Just got the bill for the specialist who came out, took the pool pump entirely apart, couldn't find anything wrong other than something totally unrelated to the original problem, put it back together and left. Fortunately it's not as costly as I was afraid of. However, the last line of the itemized bill says I am being charged $19.28 for "Air Release Valve Ass."
Given the intestinal woes I've had recently, that seems a fair price to pay. XD