When do you flush a DE filter?

[famousdavis]

My Jandy DE filter works great - sparkly clear water since we got our pool last May. After we got our pool, the DE filter had to be flushed almost immediately after the pump began running for the first time. Then, a week later, it had to be flushed again. Then again (I stupidly added phosphorous remover, which clouded up my pool and gunked up the DE filter - that about when I began spending a lot of time on this forum).

The last time I flushed the DE filter was last August. At that time, the "Clean" setting on the pressure gauge I set to 11 lbs (running the pump at 4/5th speed and valves opened to normal settings).

For weeks and week, the pressure gauge didn't budge. Always 11lbs.

Then I tamped down the pool pump to half-speed, so the gauge would read lower than 11lbs. Occasionally, I'd change the pump speed back to 4/5th so I could get an apples-to-apples comparison. It usually would still read 11lbs.

This weekend, I checked the pressure again by setting the valves to their normal settings and running the pump at 4/5th speed. This time, the pressure gauge read 13lbs -- a 2lbs increase since last August.

So here's my questions:

- How quickly does a DE filter need to be flushed under fairly normal conditions? Is it unusual to wait months between flushings?

- How many lbs over the "Clean" setting do you allow the filter to operate before flushing? My gauge says "Dirty" is 10lbs over "Clean", so it seems there is still a long way to go.

- Is there a reason why I'd want to flush the DE filter before it reaches its "Dirty" setting (however "Dirty" is defined) just because so much time has passed since the last flushing? I'm wondering if sediment inside the filter can calcify or otherwise impair the operation of the filter.

Thanks!

[waste]

Sounds like your filter is working and behaving properly

If you have a small amount of debris getting into the pool, you an go for months without having to backwash. A few years a go I wrote up the Use and Care directions found in this sticky.

The benefit to backwashing before the gauge rises ~8 psi, is that you can get a more complete/ thorough cleaning. If you go this route, you'll need to add closer to 90% of the recommended DE when you recharge the grids.

I will always recommend taking a DE filter apart and manually cleaning it at least once a year - it lets you check what's going on in there

[waterbear]

I will always recommend taking a DE filter apart and manually cleaning it at least once a year - it lets you check what's going on in there

At Least! Personally, I feel a DE filter should always be broken down for cleaning and only backwashed in situation where you are filtering a lot of gunk (dead algae, phosphate remover, etc.) that causes a fast filter pressure rise repeatedly and then, once the problem is solved, it should be broken down.
The reason is that you never quite know how much DE you are flushing out when you backwash so you never REALLY know how much you need to recharge which can lead to an undercharged filter (and fouled grids) or an overcharged filter (and DE bridged between the grids. In base cases it needs to be chipped out with a screwdriver or something similar!)

[famousdavis]

Okay, so it sounds like I don't need to sweat the long period of time between flushing.

As to the filter breakdown, how hard is that for someone who isn't mechanically dexterous? ;-) The pool maintenance guy that the pool builder sent to balance my water once the pool was built said the breakdown should be done once a year. I'm okay with paying someone to do that rather than risking damaging the filter because of my own ineptitude.