I have a Hayward sand filter for my above ground pool. I`ve just replaced the sand. The system works on filter but the pressure quickly (4 hours) dropped from around 13 psi to 10 psi.
The main problem is that the filter will not backwash. When I place the valve in the backwash position, there is no pressure and no water coming out of the backwash line.
Thanks for the question
Has the top valve been taken apart? If it has, the postion of the inside diverter may not have been replaced correctly. Be sure that the solid portion of the diverter is lined up with the 'Closed" port on the valve. Once this is done everything else should be lined back up in the correct position.
Dropping pressure could indicate no water entering the pump. Empty the skimmer basket and the pump basket. Does the Multiport valve "click" into position? If it doesn't, the valve might be worn out. Also, check the spider gasket in the Multiport valve and replace if needed. The compression plate and compression spring might be going as well.