Recently installed a new DE filter, valve, and associated plumbing. Sealed all fittings (pvc) which included removable unions with orings lubed and tight. Started the system, all functioned perfectly for a week and a half. My sister (she owns the system) decided the psi was too high in the filter due to dirt build up, shut the system down, rotated the valve to flush, ran for 30 seconds, shut down, rotated back to filter and restarted. This is where the issue starts. The system acts as it can't pull a prime. The stainer at the pool is clear, the strainer at the pump is clear, opened the air bleed at top of filter, plenty of air released to running water, closed the air lead, pump strainer runs about 3/4 full, pressure on filter at 5 psi drops to 2psi and alternates back and forth. Opened the bleed again to release mass of air again. Again alternates between 2 & 5 psi. Shut down, opened multi-valve checked the internal seal, ok, checked all plumbing joint and applied o-lube around each to find possible air leak.opend pump strainer, replaced oring, opened pump, checked for dirt or substances possibly impeding water flow, replaced all seals, found mass qty of silicone seal material, removed and replaced with proper oring. Finally restarted and system is still filling with air, has suction at the pool strainer, and output water flow, just at lower volume and pressure.i have been thru the system completely 3 times with the same outcome. Looking for any help or ideas on where all the air is coming from. Frustration is a issue currently as I believe I have addressed all possible causes, need some outside eyes. Also checked the pump rotor making sure it is turning and not slipping.