Was the swg off? It needs to be for the test results to be valid. What were your actual numbers, i.e. night FC, CC and next morning FC,CC?

Oh, and remember to answer duraleighs question (above)!

some grass and sand in cartridge. FC was a 1 and cc .5 yesterday eve and this morning. swc was off.

I saw that it was a month old pool. Any chance that there has been usage from people over applying suntan lotion or baby oils? Cartridge filter elements can quickly accumulate oils in the element, which will clog and cause high pressures quickly. Normal cleanings will not remove the oils. What's worse is that if you try to clean it by using a mild acid solution, it will lock in into the element pleats and make it worse. Tri-Sodium Phosphates (TSP) is typically what is used to soak the elements to degrease it, before using any acid solution to clean it.

Older elements can also clog up quickly, as the pours clog and do not get as clean as time goes on. I know this is not your situation, but it is another reason for elements to increase in pressure and get dirty quickly.

I soaked them overnight in cascade dishwasher detergent. It did help, but after a week of cleaning it, it is back up 8psi. My poolbuilder has ordered me another set of cartridges because he thinks that the sundek people may have messed them up. They put the sundek down and it rained, so they had to pressure wash it and a lot of it got into the pool including a good film of paint on top of the water that got sucked into the skimmers. I hope that is the problem because having to clean those filters once a week is not my definition of maintenance free like my pool builder was preaching before he built the pool. He told me I would have to clean those filters once every three months.