IG with 25K water, pump is OA Smith, very low flow and not pulling water from bottom of pool or skimmer. Sand filter registers 0. Used drainking blew water from pump to skimmer and from skimmer to pump and got flow both ways. Then when I turned pump on doesn't pull water from skimmer, even after priming it several times. Replaced sand in filter, cleaned pump filter, pulled pump apart, relubed seals, lubed o ring on pump, took apart 4-way valve on filter and cleaned, cannot find obstructions anywhere. Not finding airleaks above ground. Checked valves to make sure they're airtight, correct ones are on, when pumping I isolated skimmer so more suction would come from skimmer - didn't work. Isolated drain at bottom of pool - that didn't work. Replaced drain plug - that didn't work.