We have lived in our house nearly six years now and I have had a suction side leak since the day we moved in. It has driven me to the brink of insanity. It was minor when we moved in and has gotten worse and worse over the years to the point that this year the pump would even lose prime. I have changed pump seals, changed EVERY exposed joint and pipe around the pump & filter. I have done everything short of digging up the entire yard, which it turns out is what I should have done. I had nearly resigned myself to the fact that the leak must be in the skimmer or under the 8 inches of concrete and stone pool decking which would be a major ordeal to dig up and fix.
My kids had a few friends over to swim. They were playing that game where they all jump in unison and try to make the biggest waves possible. My wife happened to be in a lesser used area of the yard and heard faint surging/gurgling as they jumped! She followed the sound to a large rock, flipped it over..it got louder! She started digging and this is what she found. A total kludge by the previous owner.
There was no doubt this was the leak. It looks like he had a break and instead of re-plumbing with PVC used TWO of those rubber "fernco" pipe connectors. Unbelievable! A temporary coupler made for unpressurized waste lines, placed on a suction line and buried in the ground. Talk about the wrong part for the wrong job! Websters defines a "Kludge" as "'An ill-assorted collection of poorly-matching parts, forming a distressing whole". Yup...the word fits.
I dug everything out, re-piped with hard PVC, waited a good hour to burp the lines, flipped the switch and...no air. HOLY **** it's fixed! No more huge bubbles, no more noise, no more surging pump, no nothing! We have been SO used to the noise and bubbles. You could hear the pool pump running from inside the house! Once fixed my wife looked in the pool and had to ask "is it even working?". I had to reach into the stream to show her it's pumping better than ever! Its amazing what you get accustomed to. The silence is deafening!
So. Don't rule out the previous owners stupidity! You may have leak where you least expect it. The irony is that those two crappy connectors cost twice as much as the correct PVC fittings and some glue.