HELP: Pressure Going up after 4 hours of filter on

[empresschewy]

Our pool has had this issue all summer. After the filter is on for 3-4 hours the pressure jumps from 12 to 20 and very little comes out of the spa jets. We replaced the DE filter cartridges and all was fine for about 3 weeks. Then the pressure started jumping to 20 (Note: we did add algae killer right before this happened, but it I am not sure that caused this, probably just coincidence) , we did a backwash and all was fine for a day, then when the filters came on the next morning in 3 hours the pressure jumped again and very little was coming out of the spa jets. When I turn to vacuum only the pressure drops but at that point the vacuum starts going out of the water and sucking air. I can get the pressure to drop with even a quick backwash (about 5 seconds), but that will only last for a few hours before it does it again. The water level is fine. No visible cracks in anything, O ring on the filter is brand new. I am out of ideas ... any help is greatly appreciated!!

[BigDave]

Sounds like you have stuff in the water and the filter is doing its job. You added algae killer because you had algae? Algae especially live algae will clog a DE filter quick.

Do you have a Taylor K-2006 test kit? If you have algae, you'll need a good test kit to manage the cleanup. Accept no substitutes, not available in stores. If you buy it through this link: http://pool9.net/tk/ (http://pool9.net/tk/) the pool forum gets some coin to keep the lights on. As a trial user you'll need to copy the links then log out and paste it into the browser address bar.

What was in the algae killer? Chemical ingredients please. Also list the chemical ingredients of everything else you've put in the pool in the last couple months. Tell us how the water looks and how you chlorinate.

[empresschewy]

The algae killer was Pooltime Algicide Plus from Home Depot. It only says Copper 3.3% Other ingredients 96.7%. We normally have 2 floating chlorine tabs at a time and during the summer use 1lb of shock once per week. We do not have a good test kit but just took a sample to the local pool store. All levels were clear except high phosphates. That is an issue this pool continues to have. PhosFree helps but not to where it should be. The water is generally very blue and clear. A little merky right now from the algicide. We get an odd mix of yellow and green algae quite often.

[Watermom]

Uh-oh. Copper is not something you want in your pool water. Most people think it is chlorine that stains things and turns light-colored hair green but in fact, it is copper that is the culprit.