Just changed cartridge filters and PSI went up , not down???

[rugadog]

Hey all,
I just replaced my old 4 cartridge filters (Pentair -model# 17-8580) with new Unicel # C-7470. I nozzle spray cleaned the old ones about a month ago then re-installed them a began turning turning my pool from green back to sparkling clear. So the old, spray cleaned filters ran for a month after the pool was clean. I just replaced the old ones with the new Unicel filters. Just before I opened the filter housing the running PSI was 18". The PSI is 20" after I installed the new filters. Is this normal?

Thanks in advance! :?

 

[coloeb]

Are both filters rated for the same GPM? Is there a micron rating on each to compare? Both of these could account for an increase in pressure. Also are you sure nothing fell in the housing that could have blocked the flow a bit?

 

[rugadog]

Actually, I gave you the wrong info. for the filter I bought, it's actually Pleatco # PCC80. All three filters(Pleatco # PCC80, Pentair 17-8580, Unicel # C-7470) are supposed to be directly interchangeable, though. According to every distributor website I visit. I checked and there's nothing I dropped inside blocking flow. Thanks for the suggestions.

Does anyone have have any idea why my pressure would go up? Is this common with brand new filters?

 

[coloeb]

Do you have a guage on the supply side and discharge side of the filter? Sometimes units are set up like this to measure the pressure drop across the filter itself. It could be that the new filter has a bit more resistance to flow than the old.Was the old filter damaged in such a way that water could pass easier, like a hole?

 

[rugadog]

No, I just have the one gauge on top of the filter housing.

The old filters didn't have any obvious holes, but I didn't get a chance to thoroughly look at them. Because they were so old I put them in the trash yesterday morning and the garbageman came shortly thereafter. My filter housing nameplate shows it can handle 50", so the 20"-28" isn't going to do anything except work the pump motor harder (I guess?)