pressure rise with new sand filter

[Jeffski]

My sand filter runs at 22psi. I backwash at 30. Sounds normal to me.

[induce]

it is one of the hayward pro series S310T2. it is rated @ 50 psi.
it takes 500 lb sand. it's working great. just running @ 20 psi with pump on high. that northstar pump is moving some water.....quietly too.
does anyone show pressure when backwashing? it shows 20 then too.
the back wash pipe is only about 8 ft long and has 3 90's in it and is 1.5' pipe.
about the guage, it may be new, but it looks like the old one, they are both hayward filters, so they may be the same. it has that re-setable second hand that shows backwash time.