Why Does My DE Filter Lose Pressure

[AnnaE]

We opened our pool this year and everything was going fine. We cleaned the DE filter, put in the DE and the pressure was fine. However, after 1.5 hours, the pressure was gone. We primed the filter and then the pressure is good again. But then, it loses pressure again. Can anyone tell me what is going on? We've had our pool and filter going on 8 years. This has never happened before. We did backwash because we had a lot of algae. We put in more DE and at first, its fine, then no pressure. How often does these filters need to be replaced? Is it time for a new one? We got a new pump two years ago.

Many thanks.

[PoolDoc]

I'm guessing the problem is with losing prime, not with the filter. The filter is just where the gauge happens to be.

Check at a return, and compare flow when the pressure is high, with what it is when it "loses pressure". Low flow with low pressure USUALLY means low pump output.

A very common cause of prime-loss is a suction leak, often at the pump strainer lid gasket. If you want to send pictures of your pump, filter & piping, we might be able to spot some other places to look.

[gkrupkin]

I have same problem. DE filter pressure jumps from 20 to over 30 in like 1 hour after backwash and pump loses its prime . Pool is still dirty so that could be an issue. But when i put on recirculate I dont have any problems. I was thinking maybe my DE filter needs to be opened up and cleaned out...

[AnnaE]

Sorry I never replied back in 2012 (LOL)!. We did eventually figure out what the problem was. As I stated, we had a lot of algae. We had to backwash a few more times and add more DE before the pressure stabilized. Since that time, we haven't had another problem. We just know that when we open the pool, we have to backwash at least three to four times due to the algae built up.

[gkrupkin]

So after pulling apart my filter and cleaning it yesterday, it worked great for about 3 hours and then psi jumped to 30 from initial 20 again. What concerns me is that when it goes up like that I start noticing little air pockets in pump basket. They were not there before nor do they appear when I have it on just recirculate. I've been reading the stickies on if leaks. Am I going crazy or do I have a leak problem somewhere ? But why forest it take a few hours to show up?

[SunnyOptimism]

I have a Pentair QuadDE-100 filter and it works beautifully. I tear down and clean out my filter at the end of every swim season and my pool runs all year round.

Can you describe what you did to clean it and how you did your re-charge of the DE?

If you had a leak on the pressure side of your system, your pressure would not go up, it would go down. For your pressure to jump 10PSI like that means the filter is either picking up "stuff" (which it's supposed to do) or there's some issue with the internals of the filter.

My QuadDE uses cartridges to hold the DE unlike your FNS Plus which uses the older style DE grids. Both are susceptible to tears which can cause funny pressure problems. The top and bottom manifolds that hold the grids need to be carefully inspected for cracks and broken gaskets as they can cause a by-pass of water which would be seen as a low pressure and then, when they plug up, the pressure will rise. Also, there is an air-bleed on the top assembly that allows for air-relief (as well as the high-flow bypass air-relief valve on the top of the unit which you can do a quarter turn to open). That inner air relief can sometimes cause problems.

I'm just spit-balling lots of things that can go wrong inside a DE filter (now you know why so many people prefer the simplicity of a sand filter ).