High DE Filter Pressure - Low Flow

[jark87]

I have a 25,500 gallon pool with a Hayward DE 6020 filter. I clean the filter regularly (about once every 3 months, or whenever pressure gets to 25 psi). After a cleaning about 2-3 weeks ago, pressure rose quickly, to about 27 psi within 2 days of cleaning and flow dropped, or at least I assume so because the spa fountain dropped noticeably. I cleaned again and the same thing happened, then again a 3rd and 4th time - all in about 2 weeks. Water is clear and balanced and filter was clean when I pulled it out after backwashing. I hose it down each time and usually use a spray degreaser, but did so only on the first of the cleanings mentioned above.

I took the filter into a local Leslie's store and the service tech said it looked fine. It's 7 years old and he said they normally last 7 - 8 years, but longer if well cared for, which mine has been. He couldn't figure out what the problem, as he couldn't see any tears and suggested a service call. He thought it could be a clog downstream from the filter. I just don't want to end up spending $ on a service call only to have the grids replaced, but don't know if there are other diagnostics I can try on my own.

Question - if there is clog, wouldn't the pressure be high at all times? Once I clean the filter and add DE, it starts out normally - around 18 psi - and rises to above 25 over the course of a couple of days. If the filter grids are bad, are they always visibly worn? I did notice when spraying them off the last time that a small section "puffed out" slightly when hit with water. Sign of a tear?

Any help would be greatly appreciated!

P.S - after the last cleaning, the water seemed slightly cloudy AFTER the cleaning. DE flowing into the pool? Also, I noticed small white "rocks" in the pump filter basket. They are hard, but can be crushed into powder. Is this DE? The DE is so fine, I wouldn't think it would form into small rock-like pieces.

 

[jblizzle]

We recommend backwashing or cleaning the filter when the pressure rises 20-25% over the clean pressure. If you start at 18psi, you should be cleaning by 23psi.

If the pressure is rising, then the filter is doing its job and catching stuff that is in the water. Could be that you have a low level algae bloom and the filter is clogging up due to that.

How have you been maintaining your chemistry?

 

[jark87]

Yes, I monitor chemistry weekly, at a minimum, depending on my travel schedule. I just tested this morning:

FC - 4
pH - 7.6 (was 8 yesterday, but added acid)
TA - 70
CH - 400 (Yes, I realize that is high, but have been told that it's not high enough to deal with partial draining and refilling)
CYA 70

The primary issue I have is pH rising fairly quickly, which I've been told is a result of water passing through the salt cell. Other than regularly adding muratic acid, there's not much more that I have to do to keep the water balanced. I tried the borate approach a few years ago, as the discussions on this site mentioned that it would help with pH bounce, but it didn't make any difference for me. pH continued to rise at the same rate.

Last weekend, I added Pool First Aid from Leslie's, which was recommended by them. It seems to have worked, as psi has remained at 18 and water is crystal clear. I'm still not sure what caused the problem to begin with, though. I've never had the filter clog up so quickly and there was nothing noticeably different about the water. I was almost certain that I had a filter problem because spray from the pressure relief valve on top of the filter left a noticeable dust once dried, which I assume is DE. However, all now seems stable after 5 cleanings in 3 weeks. The only thing I can think of is that trees (cedar elms) around my pool have produced a sticky sap this year - more than usual. I suspect that could have caused the problem and the Pool First Aid cleared it up. If so, I'll consider myself fortunate for avoiding the cost of replacing the filter grids!

Thanks for the reply. This site is great when it comes to researching issues like these.