Extreme pump pressure

[poolgal]

We have a 10k gal 12x24 IG pool with a DE filter.

Our pump failed for about a week, and in that time we got some algae in the pool, and the water went green. We got the pump going again and took the DE filter apart and cleaned it (something we've done several times). Usually the pool clears itself up again within a few days. But a week later, we noticed that the pressure was off the scale and the water was so dark green you couldn't see more than a couple of inches through it.

This weekend we took the filter apart again and cleaned it all, but the pressure will max out within about 15 minutes. We've tried backwashing every hour all day long today, but when we put it back in filter mode, the pressure climbs up over the max again > 30PSI in under 15 minutes.

During backwashing the pressure is pretty low ~ 5PSI and you can see the water rushing through the skimmer. When back in filter mode the water gradually slows down until the pressure maxes out and then nothing is flowing through the skimmer.

Any ideas how to fix this problem? We're close to just draining the pool completely and staring over from square one.

[JohnT]

One of the downsides of DE filters is they clean so well they have problems with getting dirty trying to clean up an algae bloom. If the pool is still green, you haven't killed the algae yet.

Two ideas:

Have you cleaned the grid by soaking in whatever the manufacturer recommends? The grid can get dirty enough that routine brushing won't clear it up.

Are you sure you are adding enough DE after you backwash? Not adding enough DE will cause the filter to clog, and backwashing won't clear it.

As long as the algae is alive, there is no end to what the filter has to remove. Getting the algae killed is the first step, and if you have to run the filter on recirculate until that happens, that's okay.

[poolgal]

We hose off the grids to clean them. They come out as clean as they usually do, so that doesn't seem to be a problem. Also we put in 9 cups of DE which is also the same amount as normal.

Unfortunately, we don't have a recirculate option. Our system only has backwash or filter, so recirculation isn't an option for us.

We dumped in a bunch of algae killer, but I guess it didn't fully work. Looks like bleach is good for killing algae. How much should we use in a 10kgal pool? Our test kit can't test very high levels of chlorine.