Yellow Green Dust

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Wizard43

0
Jan 23, 2015
8
Spring Hill, FL
In July 2014 I bought a house in Spring Hill Florida (same latitude as Orlando but 9 miles from Gulf) with a pool (my first).

Since then I have had a recurring problem with yellow-green "dust" on the pool floor and sides. I call it dust since it swirls up like dust when gently brushed. It does not disappear. I shocked the pool once (before finding TFP) and have slammed it several times with varying degrees of success but the problem has always recurred. Sometimes the pool gets very green and sometimes the color only changes a little. The pool has a 90 sq. ft. cartridge filter, with a spare cartridge, which sometimes clogs enough to reduce suction to almost nothing while sweeping the pool. When washing a cartridge I get yellow-green water and can see green on the dirty filter. Is this an algae problem and is it likely to be "mustard" algae?

The next to last slam I used the pool math mustard slam levels for chlorine. The last time I used the Chlorine/CYA Chart by Chemgeek mustard levels and kept level above Yellow/mustard min. (except last day when problem had already returned). Both times I swept each day and changed the cartridge at least once, twice if it reduced suction during sweep. Both cartridges were soaked in TSP around October. The pool has an underwater light which I removed last time and there was a small pile of yellow "powder" under the light. I removed the light a couple of days ago and there was nothing noticeable. It is still out and will remain out until the slam is finished.

I have put all the tools and toys used in the pool in the pool during the slam for several hours and all pool clothing has been laundered several times. Make up water is from the public water supply.

I am in the process of slamming it again.

The pool is heated and is kept between 81 & 83 F. I have a 12 mil solar cover which is on the pool except during pool use or slamming. The cover came with a statement that it should only be used with a cholorine level of 4ppm (not sure of exact number but low) or less. What does higher chlorine do to a cover? I have put the cover on today as it seems to me that it needs to be slammed also.

The pool is screened and there is significant yellow-green on some of the screens. I assumed that this was pollen, probably pine, which I was used to from NH and which I have been told is a significant issue here in Spring Hll. Does that have any bearing on this problem?

The slamming instructions say to test the pool hourly. Is an hour really long enough for a chlorine addition to thoroughly propagate through the pool? When I started this slam I was trying to raise FC by 15ppm. after 2 hours it had gone up 8.5 ppm. In another hour with no additional chlorine it had gone up another 3 ppm at which time I added more chlorine thinking that some had probably been used up by then.


Test Results last few days using TF100 test kit.

1/18 10 AM FC 7, CC not checked, TA 110, CYA 30, pH 7.f, ch 275. Added 3lbs 8oz Calcium Chloride.
1/19 6 PM FC 6.5, CH 300 others unchanged
1/23 1:30 PM FC 4.5, CC .5, CH 300, TA 110, CYA 30 Added 2.25 gallons 10% liquid chlorine
1/23 3:30 PM FC 12.5
1/23 6:00 PM FC 14.5 Added 3qts 10% liquid chlorine
1/24 7:45 AM FC 17 Added 1.5 qt 10% liquid chlorine

Suggestions?
 
Welcome to TFP!

Both regular and mustard algae would completely disappear while you are at shock level. Or to be a little more precise, once you vacuumed up any current algae, no further algae will appear while you are at shock level. I'm not sure I follow your description exactly, but you appear to be saying that the "algae" re-appeared while still at shock level. If I am correct about that, it is not algae, but is instead dust or pollen of some kind that is blowing into the pool.

An hour with the pump running is more than enough time for chlorine you have added to the pool to mix throughly and show up of the test. You want the pump running during and after adding chemicals. If the pump is not running, added chemicals will mix only very slowly, possibly as long as days, and you risk damaging the pool surface.
 
I live in Argentina... and I've had the exact same problem as you. It's some sort of dust/dirt/pollen mixture as I only get in with huge wind storms.
My solution: Use a flocculant product, let it act and vacuum to waste. Sometimes I have to repeat the vacuuming because when you vacuum if you do it fast the dust swirls up... Good luck!!!!!!
 
Welcome to TFP !
I'm leaning towards a pollen problem and not an algae problem. Like Jason stated you wouldn't have recurring algae at shock levels. The same stuff on your screened enclosure is probably the same stuff that's in your pool.
Try using a skimmer sock or a nylon knee high stretched over your skimmer basket. It'll catch a lot of junk before it sinks and before it hits your filter. Just make sure to check it pretty often on high pollen days as it will restrict flow to your pump when it's full of pollen and other stuff. I use them all the time and they work great.
On high pollen days run your pump a little more so you skim more of the pollen off the surface before it has a chance to sink.
I'm also thinking that your cart filter is a tad too small for your pool volume. Something in the 125-200 sq-ft range would be better. Less cleaning.
 
The not disappearing was in response to a post (somewhere here) about dead algae that I may have misunderstood. I interpreted it to mean disappearing as soon as disturbed. I don't know about previous slams but the pool was vacuumed yesterday afternoon and above shock level all night. There was no reappearance this morning. My understanding is that the cartridge volume has to match the filter volume and to increase it I would need to buy a new fixture. There was one cartridge left here with a higher sq. ft. rating and it significantly reduces the flow so I do not use it. Am I wrong about cartridge matching filter spec? Why does it keep coming back after it goes below shock?
 
The filter is a Hayward C9002 cartridge filter which the label says takes a 90 sq ft cartridge. The pump is a 1 HP Flotec which was replaced just before I purchased the house. The filter housing also appears quite new and the old one was left behind, but I do not know exactly how new. I have used the OCLT test during past slams. I had not bothered until last night since there was enough "dust" left to show that I was not done. The results last night were: at 7:00 PM Monday 1/26 FC: 19, at 6:30 AM Tuesday 1/27 FC: 16.5 so something is using up chlorine over nite. As I think about it, it seems that the problem cannot be mostly pollen because the pool is covered now except when in use or getting chemicals. In the previous instances I did not have the solar cover as I was not heating the pool. The cover does not fit tightly enough to prevent all outside material from getting in, but it seems very unlikely that I can get enough overnight to cover the sides and bottom of the pool completely. Each day I am getting less material to vacuum up and today I did not get any overnight last night. The real puzzle for me now is how to keep this from repeating. since the last slam I have been keeping the FC above 5 which is the minimum for yellow mustard according to the Chlorine/CYA Chart by Chemgeek fro a CYA of 30. It's possible that my last slam was not totally effective, but I had passed the OCLT test for 2 consecutive nights before I stopped slamming. I know there has some discussion in the forum as to the validity of the OCLT test, but what else do I use. I don't believe I should keep the FC above the slam level of 18.2. Thanks for all the responses. Suggestions welcome.
 
I am still fighting the battle. It seems quite clear now that I am fighting algae, probably mustard. I have been trying to keep FC above the 18.2 ppm mustard shock level with CYA of 30, but life has gotten in the way a couple of times and it has slipped as low as 16. I have been testing FC night and morning and have not seen FC go down by less than 1. Last night at 7:30 PM FC = 21.5 this morning at 7:30 AM FC = 19 so it seems that I have not won yet. I am not seeing any "dust" when I sweep now and I let sweeping go for a couple of days, but re-reading the sticky articles about defeating algae I realize I should sweep every day until FC stabilizes over night. I also shut off the pump a couple of nights to keep the heat pump from frosting up but now I realize I should just shut off the heat pump. I have proven that running the heat pump with air temp below 50 F produces a white heat pump.

I have noticed that it takes several hours for FC to peak after a chlorine addition. I have been pouring the liquid chlorine into the pool in front of one of the pump outlets. Should I put it into the skimmer instead? Many articles talk about testing after an hour and that does seem to not produce valid results for me.

Any other suggestions?
 
If you haven't already, make sure you read the Mustard Algae article in Pool School. There are several special procedures for fighting mustard algae. For example, there is no point in keeping FC above regular shock level until you don't have any overnight loss. Through daily brushing is also critical.

Taking several hours for FC to "peak" after addition makes no sense unless your circulation is unbelievably bad. Bleach/liquid chlorine adding by pouring slowly in front of a return jet with the pump running should be throughly mixed into the bulk pool water in half an hour or less. You may want to check your circulation pattern with food dye. A small bottle of food coloring adding in front of a return jet with the pump running should be visible throughout the pool in under five minutes. Food dye is harmless and will break down very quickly in a pool. If it is not mixing well you will want to adjust your return jet aiming to create a consistent water movement and mixing until the dye test shows rapid mixing. Usually aiming the return jets to create a consistent circular motion is best, though complex pool shapes often require more complex strategies.
 
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