Low start-up pressure

[Pool in Carolina Blue]

My DE filter has a typical start up pressure of 18. Recently the start up pressure dropped to 15 or so which has never happened in the two years I have operated my pool. The flow in the returns is good and I see no air bubbles in the return lines and pump basket.

Any idea as to why the drop? A few months ago I switched to cellulose fiber filtering media instead of DE as it is a little safer and does a better filtering job. The start up pressure remained at 18 until recently though so I don't believe it is the filtering media?

Thanks for any thoughts,

Mike

[Poconos]

All I know about DE filters is what I have learned here on the forum and I have a sand filter. My first guess would be a torn or damaged grid or whatever they use. Easiest way to check is to throw some DE powder into the skimmer as usual then watch the return jets. If you see DE coming out then something is damaged. Otherwise, it's probably filtering OK. 3 psi isn't really a big change but it could be an indication that something is wrong if you have a long history of readings.
Al

[Pool in Carolina Blue]

All I know about DE filters is what I have learned here on the forum and I have a sand filter. My first guess would be a torn or damaged grid or whatever they use. Easiest way to check is to throw some DE powder into the skimmer as usual then watch the return jets. If you see DE coming out then something is damaged. Otherwise, it's probably filtering OK. 3 psi isn't really a big change but it could be an indication that something is wrong if you have a long history of readings.
Al

Thanks Al. Nothing came out the return jets and the grids appear to be okay. I have two years of readings so this drop, while not that significant, is somewhat baffling to me.

[Poconos]

Any chance the pumps impeller could be crudded up with stuff that made it past the pump basket? Did you run at any time without the skimmer basket in place so something could have lodged in the skimmer pipe? Otherwise I'd just keep an eye on the pressure and see if anything more changes. I wouldn't lose sleep over it.
Al