Does air in the suction side mess up a DE filter system?

Several years ago we replaced the pump on an in ground pool with a DE filter. The new pump does flow more water and things were fine for the first season and then pressures would go up, output would decrease and the pool would get green. The DE would get changed with a grid cleaning and things were OK for a mounth or so then green pool. The grids were changed as we noticed DE in the bottom of the pool. Now we are back to high pressures, low flow, air on the suction side (the leaf trap on the pump has an air pocket), geen pool. The pump is just barely below the water level in the pool. Did I get sold a pump that is to big? It is a Whisper Flow 3/4 hp with 1&1/2 inch piping. Tom
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On 8/28/2013 3:44 PM, Tom wrote:

You should have a air release valve on the top of the tank.
http://www.azpoolcare.biz/graphics/de-filter.jpg
If you do have air in your system it's most likely a gasket, cracked valve lid, or a leak in a union.
With all that said: I'm not sure you'd have high pressure if you have air in the system. Seems counter intuitive to me but, I don't have a DE filter. I have a sand filter.
As far as your pump, have you had this problem since you purchased the pump? Sounds to me more like a filter issue. Are you still getting DE in the pool?
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“,… air on the suction side (the leaf trap on the pump has an air pocket)”
I assume that you mean the skimmer is sucking air. Have you tried overfilli ng the pool or removing the weir? Is the main drain on the bottom of the po ol blocked somehow?
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On Wednesday, August 28, 2013 4:44:01 PM UTC-4, Tom wrote:

You have an algae problem and it's probably not caused by the filter, but it's clogging it up quickly. Are you maintaining the pool chemistry? Checking it 2x a week, daily if it's not right until you get it corrected? Shocking periodically? What is the CL level? I recommend getting a Taylor test kit that does all the necessary tests and doing it yourself. It's easy, you can do it any time, a $50 kit will last several years.
Any exceptional runoff going into the pool when it rains, eg from some shrub beds or similar? How many hours a day are you filtering? Rule of thumb is you want to filter enough to equal the volume of the pool each day. I've seen pools that could get away with less than that and still not have problems.
You need to deal with the algae. First rule is to make sure you keep the chlorine level in line. But once you have algae, normal levels won't eliminate it. You need to shock it and depending on how bad it is, I'd take the chlorine up to 10ppm to 25ppm level. The other approach is chemical. There are two chemical approaches. You can either add a phosphate remover to eliminate the food source for the algae, or you can add a algaecide that kills it. I prefer the copper based ones, they have worked for me. But then I rarely have an algae problem. A lot depends on your environment.
The DE would get changed with a grid cleaning and

Do you mean backwashing? Normally you backwash as needed when the pressure rises to about 10psi over the level it starts at when it's clean. And the filter gets taken apart for a manual cleaning once a season. Since you're having problems, I'd probably deal with the algae first, get the pool mostly cleaned up, then take apart the DE filter for a manual cleaning and inspection.
The grids were changed

Grids should last many years. Here the filter is now about 8 years old. It's about due for replacement. I think it's also possible for DE to get into the pool if the multi-port valve is bad. That valve controls where the water goes and I think if it's bad then when you're backwashing for example, some of the water could go to the pool instead of to the waste.
If you have the typical kind, they are easy to take apart and check. Should be a bunch of bolts holding the top on. You remove them, then the lift the whole thing out. Don't worry, there aren't a lot of little widgets that are all going to fall out ;) At the bottom of the housing there should be a spider gasket. Makes sure it's where it belongs, not torn, etc. Also make sure the shaft of the valve is lubed with some Teflon spray. It's spring loaded and if it's not free, the plate won't seat against that spider gasket and water can get anywhere in the valve.
Now we are back to high

Sounds like the algae problem is clogging the filter. As soon as the pressure rises 10psi, it should be backwashed. Are you doing that correctly? You backwash until water runs mostly clear, then go to rinse for maybe 15 secs, then back to backwash. Repeat that cycle until it runs clear. Only move the valve with the pump off.
Is the flow OK after backwashing? Or is there something else going on?
air on the suction side (the leaf trap on the pump

The most common source of air is the strainer top not being sealed. Take if off, remove the rubber o-ring, clean it all and try again. Make sure it's tight. If you still have a problem, try putting a thin coating of Teflon lube on the o-ring.
I wouldn't be worried about a quarter size bubble at the top. If there are no leaks at all, normally you would not have even that. But if there is a significant leak somewhere, then you will see more air and even bubbles coming in.
The pump is just barely below the water

I guess that depends on how big the pool is. Hard to imagine it's too big. IDK if they come any smaller, that's probably more common in an above ground. The ingrounds that I've seen typically use 1hp, some more than that.
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On 8/29/2013 9:17 AM, snipped-for-privacy@optonline.net wrote:

I agree with the environment comment. I seem to have more algae issues around this time of year but the trees here like to dump stuff almost year-round here. I never have used algaecide. I don't even think about it. I'll check the phosphates, balance the chemicals, then shock. If that doesn't do it, it's got to be a filter issue. Which I have had.
Once he does get the algae controlled he'll have to remove the itty-bitty dead algae carcasses. I've never used DE but I did just recently add 3 cups of Zeofiber to my sand filter. The stuff works well. Cleared my pool in a couple of days and it's a pretty cheap fix. It's supposed to work in DE filters too.
http://www.poolplaza.com/mm5/graphics/filter/ZEOFIBER3-F.jpg
I got mine at the pool store for about $13. There appears to be enough in a bag for a few years. But the OP needs to get his pool chemicals right first. It's not a miracle cure. :)
<Sniped the rest, but it all seems like good advice to me.>
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