Adding DE to sand filter didn't increase pressure

[I.Robert]

Hello,

Thanks to TFP, I've had sparking water, at least up until this very hot summer.

I got some fine green sediment a couple times, which got kicked up while vacuuming, and now I just can't get the water clear.

I shocked and ran the pump for three days with little improvement. The water is clear in a glass but cloudy and pale green when looking through to the bottom steps.

The water is balanced and there is no increased chlorine demand.

I read here that perhaps my sand filter is not performing, so I went ahead and added some DE as per Pool School:
Pool School - Add DE to a Sand Filter

After adding three cups, the pressure only went up at most 0.5psi. So I stopped adding.

What should I do? Should I keep adding DE to get the 1psi increase?
I did not see any DE coming out the return.

The sand is definitely 5+ years old. I think it's at the correct level. I'd like to avoid pulling the valve if possible until closing time.

FC:6 CC:0 pH:7.7 CYA:35 TA:80 CH:150

Thanks!

-Rob

 

[woodyp]

Adding a bit more won't hurt anything to see if it will rise. It'll all backwash off the top anyhow. Mine, 250lb filter, takes more than that to effect the pressure increase.

 

[I.Robert]

Thanks, woodyp!

So I think I either did a real bad job at reading the gauge, or it took a while to register.

I added another cup and noticed it increase by about 0.5psi. I also noticed the return was lacking pressure and the pump wasn't pulling much water.

I did a short backwash & rinse and got my return pressure back while losing almost 2psi on the gauge.

Lo and behold, the magic number is probably 2 cups

-Rob

 

[I.Robert]

I'm amazed at how well the DE worked. In just one day, the sparkle is back!