Have 2 gauges

[Sugarfoot]

I see that most pool set ups have one gauge at the filter. Mine came with a gauge at the control valve and one at the filter. Both gauges read the same until one month ago when the gauge at the control valve read 40 after backwashing. I believe my 1.5 hp pump may be too big but it didn't show any signs of being too big the first year. I'm wondering is I have something clogging or causing too much pressure before the water gets to the filter, thus the high reading at the valve and not the filter?

Gauge at control valve quit working. Gauge at filter is working well.

 

[Bama Rambler]

Does the gauge go to zero when the pump is off?
Does it constantly run at 40 or did it just spike up there that one time?

 

[Richard320]

I think you got a bad gauge. Everywhere from the pump impeller to the dirty side of the filter is going to be at the same pressure when the pump is on.