sand/dead algea in bottom of pool?

Jul 30, 2009
24
Hello to all in the known how.
First time poster, long time reader. Bought a house a few years back and maintaned a trouble free above ground, vinyl liner, 21" pool for those few years. This year upon opening the pool after our winter, everything was reconnected as usual and water was balanced as per pool store recommendations and water was crystal clear and balanced with in 48 hrs. Since opening the pool, over time little dark cloudy dust forms in patches around the pool, it appears to form in the direction of the water flow from the return line. :( I've since vacuumed it on drain and clean once again. Although this dust reappears over time. At first it's in very little patches of dusty dark spots, sometimes greyish white, once brushed, the seem to dissipate but I'm not sure if they go away or just fall right back on the ground. At first I thought ok, sand in filter change. That was done and manifold was carefully inspected and appears to be in good shape. No water leaks anywhere and pressure gage works adequately. Still, this sandy stuff still reappears. Since opening the pool, vacuuming to waste has become a weekly event now (kind of a drag!) and if I dont vacuum, the entire floor will fill with this slimy dusty stuff, in patches in circular direction. Back washing every week now after every vacuum even though pressure gage isn't above 15, the clear bubble indicator shows alot of stuff getting backwashed. I backwas for 5 minuts and rinse for about 2 minuts. This was also done when the sand was changed (the right amount was used).

Any help or advice would be greatly appreciated. I've even considered replacing the filter to a cartridge system, because I don't know how old the filter is, but I'm sure it's still in good condition.
 
If you could suck some up into a turkey baster, or something similar, then put it into a glass jar, you could better determine if it's sand from the filter, or algae. Then you could get mechanical help, or chemical help.

Also post details about your pool, and test results.

Dan
 
from what i can gather just by brushing it... looks alot like dead algea but it's hard to tell

chlore: 1.5ppm
ph: 7.2
alcalinity: 10ppm
hardness: 250ppm
these tests were performed at a local pool store this afternoon
 
there's not really an option to not knowing your cya level if you're going to use this method. I mean you could shoot in the dark, but if you're wrong you're wasting any money spent. this is one of the reasons the site recommends getting a good personal test kit, so you can know your numbers and take control of your pool.
pool-school/pool_test_kit_comparison
I highly recommend the tf100, it's a much better value.
 
Bob_Funk said:
helpmeplease said:
a stabilizer was used early in the pool season

How much CYA did you add?
if i remember correctly it was 1.5 kg of stab for 40000L.

today i vacuumed the pool again and was all clean till the pool pump/filter went on for it's daily run... well seems that the bottom of the pool only gets dirty when the pool pump/filter run.. i guess that is a clear indication that the filter is not running properly is it not?
i see no dirt or dead algea forming or accumulating when the pump/filter are off...
 

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by adding 600g of hth shock powder all around the pool
noon here now.. chlore maintaining at 2.5ppm
just as the pump started , the entire bottom filled with a light dirty film.. after brushing it, it seems to have dispersed.... i am leaning towards a faulty filtration system after the sand was changed at the beginning of the season
 
Does it come back only on the bottom of the pool and only in the dips and divets in the liner? IF yes...it is dirt/dust or pollen from the air. Put a skimmer sock over your skimmer basket, and you will see that go away. You will see it all collect on your sock...But get that chlorine up to shock level...POOL SCHOOL! and get a good test kit :goodjob:
 
what about the bottom drain? is covering the skimmer basket really enough? does that mean the dust/pollen goes through the skimmer and is thrown into the water in the return line? why wouldn't this get picked up in the filter?

these were the results from my latest water test at the pool store
chlore: 3ppm
ph: 7.2
alcalinity: 100ppm
hardness: 250ppm
 
You can rig a nylon stocking to fit over the return flow and see what is coming back thru the return, if it is a filtration issue.

Sand filters, especially new sand, don't always filter the small stuff which is why we recommend skimmer socks and other "tricks" to improve filtration - like adding DE to the sand (instructions in pool school).

I'd recommend you invest in your own test kit.

Please take a moment to add your pool's specs to your signature. Go to User Control panel, then Profile, then Edit Signature. :wink:
 
frustratedpoolmom said:
Sand filters, especially new sand, don't always filter the small stuff which is why we recommend skimmer socks and other "tricks" to improve filtration

sock has been installed... can't tell yet if there is a improvement with the sock on
how long before new sand in a fiter starts "to filter the small stuff"
 
helpmeplease said:
frustratedpoolmom said:
Sand filters, especially new sand, don't always filter the small stuff which is why we recommend skimmer socks and other "tricks" to improve filtration

sock has been installed... can't tell yet if there is a improvement with the sock on
how long before new sand in a fiter starts "to filter the small stuff"

You should see a difference overnight. What kind of area do you live in? Are there lots of trees? Do you have farm fields nearby? In the spring and early summer I have a great deal of dust and pollen. Before I turn the pump on I can see it all floating on the surface of the pool. What happens is that if the pump is not running, it all eventually sinks. It is the same thing if you see a dark car in the summer it usually has a nice coat of dust on it. The pool acts in the same way. The waters surface traps any dust in the air...when it is really bad, I run my pump 24/7 with a sock in place. That really helps...It is like pealing lint off the trap in your drier.
 
Earlier in the season, our pool was a bit cloudy, so I added half a gal of bleach/day and ran the filter 24/7 for a few days. Which should have been bringing the FC up to about 4 ppm. No Help. I thought the bleach might be old, so I went and bought fresh bleach, and added 3 gal. Which would have brought FC up to ~15. The pool was crystal clear the next morning.

You said it was slimy, so we'll assume it's algae for the moment, not filter sand...
If your CYA was at 0 and you added 1.5 kg of CYA - that would be about right. (40 or so). 5 ppm FC would be good goal for you. (You really need to get a good CYA #, though.) Each time you've posted your Chlorine number it was less than 3 ppm. If your pool is 40000 litres, (we'll assume CYA of 40) try adding adding 10 litres of 6% bleach (normal, unscented). Run filter 24 hours.

Also, after re-reading your previous comments, you could have a broken filter, AND algae. Tell us if the sock picks anything up. Also, don't put your test results in your signature.

Dan
 
Just backwashed and pressure guage was reading 20... after several minutes and alot of green stuff beeing backwashed through the looking glass valve, then rinsed the guage is now reading 18... backwashed some more and re-rinsed but the guage maintains a reading of around 18psi. When pump is off it reads 8psi and when the filter turns on it jumps right back to 18. Could this be of any help for diagnosing a possible filter failure?
BTW, the surface water is clean and clear and I do live in a heavily wooded area.
 

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