DE filter pressure drops after running for a few hours?

[John Knight]

I’ve got a DE filter and noticed something odd this week. When I start the pump pressure reads normal. After a few hours, it actually drops a few PSI instead of rising. Water still looks clear and flow seems okay but I always thought pressure was supposed to climb as the filter gets dirty. Is this something to worry about?

 

[Joe Smith]

I’ve got a DE filter and noticed something odd this week. When I start the pump pressure reads normal. After a few hours, it actually drops a few PSI instead of rising. Water still looks clear and flow seems okay but I always thought pressure was supposed to climb as the filter gets dirty. Is this something to worry about?

Pressure dropping instead of rising can sometimes mean there’s air getting into the system. Check the pump lid and any suction side fittings for tiny air leaks.

 

[Warren Dale]

I’ve got a DE filter and noticed something odd this week. When I start the pump pressure reads normal. After a few hours, it actually drops a few PSI instead of rising. Water still looks clear and flow seems okay but I always thought pressure was supposed to climb as the filter gets dirty. Is this something to worry about?

It could also be DE shifting inside the filter if there’s an issue with the grids. I had a small tear in one of mine and pressure behavior got weird before I figured it out.

 

[Danny Meerman]

I’ve got a DE filter and noticed something odd this week. When I start the pump pressure reads normal. After a few hours, it actually drops a few PSI instead of rising. Water still looks clear and flow seems okay but I always thought pressure was supposed to climb as the filter gets dirty. Is this something to worry about?

Another possibility is that your gauge isn’t super accurate. Mine was sticking and giving inconsistent readings. Swapped it out and realized the pressure hadn’t actually changed much at all.

 

[John Knight]

Interesting, I hadn’t considered the gauge itself being off. I’ll inspect for air leaks and maybe replace the gauge first since that’s easy. Appreciate the ideas.

 

[Oscar Ricci]

In a situation like this, I’d actually look at possible return-side flow restriction, not just air or the gauge. I once had a slow pressure drop because of a slight internal bypass in my multiport valve, so not all the flow was going through the DE media. The water stayed clear, but pressure would fall 2–3 PSI after a few hours. If flow feels steady and there’s no air in the system, it’s usually not urgent, but definitely worth checking before it turns into something bigger.