How to tell if vacuum is working

Sometimes I vacuum and plenty of debris winds up in the skimmer sock when finished. Other times practically nothing! I do the same process every time (submerge vachead and hose, fill hose with water from eye, keep hose end in water as I attach to vacuum/skimmer adapter, begin vacuuming.) I thought that if I didn't see the debris cloud up as I brushed over it that it was being sucked up. But that's not always the case. I even try to just lift the vachead over the debris spots and just press down to avoid having the brush spread the debris. But there are still times I vacuum for for a half hour only to get nothing in the sock! My question is, how can I tell that the vacuum is actually cleaning while I work? Secondary question, If I hear the pump water flow interrupt while working (it makes an oscillating sound) did I lose suction and should I start over? Thanks for the help!

Did you backwash before vacuuming?

No. I don't backwash ever. I don't even know how to with my equipment (no backwash setting on my pump.). I simply hose down my cartridge when pressure gets 10 above the starting pressure. But I want to learn why some attempts at vacuuming work fine and others don't. Thanks!

I found that trying to fill my hose from an eye with the other end attached to the vac head and submerged depends on how deep the head is and the pressure at the eye. You have to overcome the water pressure at the bottom in order to fill the hose. Now I fill the hose while holding the other end nearby, when its full, I connect to the vac head and drop it in, then the other end to suction.

I also close off (mostly) the other suction points (main drain and second skimmer) so the vac head gets all the flow. I usually look for a small piece of something for the vac to pick up.

If you get nothing in your skimmer, is there still dirt in the pool? If so you're not vacuuming.

I'm thinking you're not filling the vacuum hose with water so there's air. Easiest way is to hold the hose over the return until it stops bubbling then keep the hose underwater and plug it into the skimmer.