DE filter turned green after three weeks since my last cleaning!

Lonnybass

Silver Supporter
Jun 26, 2018
78
San Diego
Three weeks ago, I broke down my DE filter and did a full cleaning of the grids.

In the last 10 days or so, I noticed that my pump performance had deteriorated significantly. When I opened it up today, I was greeted with the horror show below. I'm kind of shocked - especially considering that my pool water has been sparkling, no signs of algae or cloudy water, combined chlorine consistently at either zero or .5, nothing showing up on the walls. Is it possible that there was an algae bloom limited to the filter or hiding somewhere in the plumbing? I'm kind of mystified about this, and would love to know what to do to maintain the lifespan of the new filter media I decided to install today instead of trying to salvage these disgusting ones. Would love thoughts as to what is going on here!
 

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CJadamec

TFP Expert
Apr 29, 2016
2,390
Quaker Hill, CT
More than likely you have an algae problem. What are you current test results, and have you been going thru more chlorine than normal lately.

Good news though is your filter is working perfectly.
 
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duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
32,830
Sebring, Florida
Yep. Green = algae.

Regardless of the other indicators, you will need to SLAM your pool. Can you post current test results?
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
22,069
San Dimas, CA (LA County)
Unless the trees in your neighborhood shed green pollen, you've got algae. Go check windowsills and little-used patio furniture and that boat that sits in the neighbor's drive and never moves. See if they're covered with greenish pollen. But I'll bet it's algae.
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
32,830
Sebring, Florida
320 brings up a good point. I had overlooked pollen (it's long gone here in Southern FL) so that is a possibility.
 

Lonnybass

Silver Supporter
Jun 26, 2018
78
San Diego
Test results from this morning:

Free chlorine 4.5
Combined Chlorine 0
pH 7.4
TA 170
CH 220
CYA 30
CSI -0.04
Water temp 79

The only real surprise from my latest test is that my CYA level appears to have dropped so low. The filter had been charged as normal with DE and I was testing the water frequently last month during a stain removal treatment for citric acid.

I just initiated a SLAM to take the chlorine level up to about 12 ppm to take care of any residual issues that might be going on before they can take root on my new grids.
 
Last edited:

Oly

Gold Supporter
Jun 28, 2017
1,165
Fresno, CA
Clean your grids, raise your FC to to 6ppm then test FC after sunset using the 25ml test volume. Test FC, 25 ml volume again the following morning before the sun hits the water to measure FC loss overnight. If your loss is above 1 ppm you will need to elevate your FC, sanitize your system and SLAM.
 

CJadamec

TFP Expert
Apr 29, 2016
2,390
Quaker Hill, CT
I had considered pollen but everything around the pool should have to be coated in green pollen fairly heavily for it to have clogged the filter in 12hrs.

Starting a quick SLAM should have clean things up without too much fuss.
 

Lonnybass

Silver Supporter
Jun 26, 2018
78
San Diego
I am now 24 hours into my SLAM and I have my comparison numbers:

Evening
Free Chlorine 12
Combined Chlorine 0
pH 7.2

Morning
Free Chlorine 11
Combined Chlorine 0
pH 7.8

It's looking like I am in the clear on the algae, but I'll need to continue to bring down my pH in order to reduce the TA numbers from yesterday's result of 170.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,440
Northern NJ
Don't bother testing pH during a SLAM. pH measurements are not reliable when FC is over 10.

Don't touch your pH or TA until your FC is under 10.