What might cause the pressure on a 1 year old Hayward sand filter that has just been cleaned with a Sun filter cleaner and backwashed to remain high?

i'm not familiar with brand but no matter. what effects the influent preasure of a sand filter are preasure coming in pruduced by pump.if a valve was normally choked (not fully openned ) before to control the the flow this could be your problem. check the rating that your sand filter can handle and volume spec required by your pool/ spa. more likely especialy if a hot tub, is that due to heavy use or infrequent cleaning, your filter is still clogged. oils and greases will 'ball' and clogg filters. cleaners will not always break these down and you sand may need to be replaced. check your sand first to see if it is dirty or greasy. influent and effluent gage would help monitor your cleaning requirements. influent preasures go up and effluent preasures go down as filters get dirty. Check the gauge. We thought something was wrong with our filter and/or pump and it was just the gauge. Check to see that the pressure goes to zero when the pump is off. It sounds elementary, but can easily be overlooked.