Should I backwash??

I have an 8500 gal inground vinyl lined pool. I have a Pentair FNS 60 DE Filter. The pool was opened for the season in May. The pressure gauge on the top of the filter has been at the same pressure reading since the pool was opened. The filter instructions say to clean the filter when pressure reads between 10 to 12 psi higher than the original starting pressure. Since the pressure has not increased, I have not backwashed the filter at all this season. The water still looks clean. Should I backwash anyway just based on the volume of water that has passed through the filter since May?

Thanks

I would. It could be that your gauge isn't working properly. Does the pressure drop off when you turn the pump off? See if the pressure changes after you backwash. It it doesn't, I think I'd buy a new one. They are pretty cheap.