Pressure guage under pressure!

This will be my 4th year with my pool and starting last year I noticed that my pressure guage would reach 15 psi within a day or so after backwashing. When I first got the pool, the pressure would stay at or below 10 psi for about a week or even two before it got to 15. Now, it seems that the pressure shoots to 10 right after backwashing and goes to 15 withing a few days. I've changed the pressure guage and it does the same. Any possible reasons for this? By the way, what is a "danger zone" level for the pressure guage? I was told by my installer to make sure it doesn't get to 20 psi.

Thanks.

Is this a sand filter??? My sand filter has begun to do the same thing, and I'm wondering if I need to clean filter as I did not do so for winter maintenance.

CaryB

OK, I have NO idea why he says 20lbs is bad. Sand filter?
Your pressure gauge isn't the problem. Either your filter is clogged or you have a restriction somewhere, or it's really too small for your pump. Have you changed pumps recently?
A sand filter may have gummed-up sand, or broken laterals. DE filters may have hard crusting on the screens. Cartridges may be clogged beyond what hosing-off will clean.

Sorry for leaving out the fact that yes, it is a sand filter. I have not had any change in pumps and, as stated in my original post, everything worked just fine the first two years. Are there tests that I can have done to the system to see if there is a blockage somewhere? By the way, when I backwash, I normally fill the pool to the point where I can backwash for a good 15 minutes before the water level returns to normal.

Thanks for any tips/suggestions.