Just installed a new sand filter after old cartridge filter died (it was 26 years old).

While I love the ease of backwashing the sand filter, I am finding that I have less flow through the system with this new filter even after it is backwashed.

Once backwashed its "zero" is at 20 on the pressure guage, and when it goes up even to 25 the flow just stops. In the 6 days I have had the filter, the flow has come absolutely to a stop on at least three occasions (and does so each time after running the Polaris for any extended period of time).

Is this an issue with the size of the filter?