When to Replace vs. Clean DE Filter?

This started out under the thread "The Long Road in Trying to Lower TA," but more underlying problems might exist with the equipment, so I decided to move to this section to stay topical.

Problems
• DE won't cling to the panels. As I pour DE into skimmer, I see it shooting out immediately out the returns. It then just falls to the pool floor, and the whole floor has a white coating, although it doesn't cloud the water. It ultimately ends up in my vacuum bag. I assumed that my CC would start climbing, but in fact it actually disappeared when the new partial panel was installed.
• DE pressure never rises beyond the 10 psi that it started off at when we installed the new panel, even though the DE is not coating the panels.
• Do all the panels need to be replaced? (Very last resort) The manifold has a small crack on the top of it, but it doesn't seem to affect it in my opinion. Maybe they simply need a chemical cleaning. I saw that Ted gave a nice explanation of this.
• We had been running the equipment around the clock since we opened it in early May, but since it has been clear and nicely balanced water in July, we attached the little timer pieces so that it runs about 12 hours every night. Every morning I find that the pump has lost its prime. What are the ways it can lose its prime? It never lost it when we ran it around the clock.

So, it looks like I have 2 problems here:
1) DE not coating panels
2) Pump losing its prime when on timer

Thank you,
Shannon

Bumping this up to see if someone can reply for you.

Losing prime is due to an air leak somewhere. Be aware that a leak that seems insignificant for water, such as a drop every couple minutes, can be significant for air. Over the 12 hours the pump is off even the slightest leak will probably cause the water to drain out of the pump basket and lose prime. As for the DE problems, I'm pulling a Sargeant Shultz...I Know Nothing.
Al

Al, you were right, and here is how I found out where the leak was.

The first thing I did was swap clear dome lids between the main pump and the twin that runs the deck jets. The pump continued to lose its prime within hours of being turned off, so I knew that there must be an air leak somewhere else. Next, I let the hose gently run over the equipment in various places, but I never saw any noticeable bubbling to lead me anywhere. Upon leaning in closely, like some kind of ease-dropping detective, a faint high-pitch sound was heard at the Jandy valve that controls water flow from the skimmers and main drain. We took the valve top off, inspected the o-ring, and discovered that it was cracked! Since the set-up is twin to the deck jets line, we moved the o-ring from that one over to the main pump, and it hasn't primed this nicely since the first year we opened the pool! I so appreciate the care and help on this forum. Thank you for teaching me along the years.

Shannon

Sounds like you found your problem.
However, just in case, I've also found another thing that causes air leaks.

This has happend to me and took a while for me to figure it out.

Not sure what kind of valve's they are (I think Jandy), but the valves that allow me to control my skimmers and main drain have been the culprit in the past. These valves are the type you have to loosen a little before you can open/close them. Well sometimes, if they ae too loose they allow air into the system. Funny thing is they do NOT leak. So when my filter looses suction after being off for a while and won't prime on it's own, that is usally the first thing I check, and 9 times out of 10 it is exactly that. The other 1 time was that the O-ring on my pump was worn.

I'm thinking this should be a "sticky" as one of the first things to check when a filter won't prime. What do you think? :)