CYA coming back through returns?

[HooStat]

The water comes from the skimmer and/or main drain and into the pump. From the pump it goes to the filter and then to the heater. From there it goes to either the infloor system or main returns (depending on valve settings).

For the spa, the setup is the same except that the water comes from the spa drains and goes back via the spa returns.

This seems like it should be pretty standard. Am I missing something?

Just added: backwashing is done by moving a lever on the filter. when I move the lever, the backwash goes into the drain instead of the pool.