Pentair 60 SQ FT FNS PLUS top swelling

[hjlumber]

For the first time since 03 when the pool was put in, I noticed that the top swelled when I turned on the pump. it swelled up about to about 1/4 " taller. I had backwashed the pool and started it back up. the De was going back in to the pool also . So I backwashed the filter again and it did the swelling a little less. Also the DE did not go into the pool the 2nd time. I think maybe the DE was not mixed enough and it clogged things up momentarily . I have not had any problems with high pressure. The pressure stays in the low 20's all week .Is this swelling normal or is it just time to replace the case after 13 years ? sure don't want it to blow up and explode.
thanks !

 

[pool&spatech]

what is the pressure when you backwash, high 20's - 30 then it gets back down to low 20's ?
low 20's to me sounds high for normal psi, and if your back washing when its in the low 20's and after your done bw, it is still in the low 20's then you need to take filter apart and clean or whatever it needs, being that i don't have any idea how valves are set or this, and that, on your pool.

Has the filter ever been torn down for service before?