I have an IG true-L shape pool with vinyl liner. It has a return line for the steps with 2 jets. They both shoot out at 'normal pressure. Never problems.
The other return line has 3 jets, 2 in the shallow end, 1 in the deep end. The 2 in the shallow end shoot out at 'normal pressure' but the deep end one does not.
When the pump first starts, all 3 jets have normal pressure. When the deep end loses most of its pressure (maybe 1/2 hr later????) I can cover it with my palm and feel pressure building, air bubbles will eventually come out the low end jet closest to it in the shallow end. Then I remove my palm from the deep end jet and all 3 jets have normal pressure again.... then the problem reappears in about 30 minutes.
Pressure at the filter is 18psi which it has been for years before the problem appeared(problem appeared this year only)
Any ideas about troubleshooting?
If it helps, the problem jet is closest to the pump/filter. If I move the valve on my plumbing to turn off the return line for the jets at the steps I have real high pressure on the return line with the 3 jets and no problems.