Brown dust

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simonoaks

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May 28, 2015
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Juno Beach , Florida
Hi,

Been maintaining my own pool for 3 years now, using all the methods on this site. Even over winter I test FC 3 and PH 3 times per week , and TA monthly. Just tested CYA last week for first time in 3 months and it was down to around 30...which explains why my FC dropped from 6 to 1ppm.

Anyway, added CYA and some bleach to get FC back up , last week, and now just playing around with SWG to get the % right based on CYA of 80 now.

So, my pool has always been crystal clear and bright, but I just noticed, the last 3 times I have brushed the sides and floor in last 5 days (I must admit , I went a month without brushing ) , I get a brownish/ greenish dust that comes off the walls and floor. I can even see areas where I missed some brushing (hence doing it 3 times in 5 days ) . My question is, could there be something wrong with my filtration system if I am getting these small brown dirt particles ? Should they not all be washed through and filtered out? Just seems odd , as I presumed that brushing it all up would make it goes through the filter system.

thx
 
Greenish dust sounds like algae in its early stages. When your CYA dropped, followed by your FC which was well below the TFP minimum, it probably let the algae bug in. Ideally, you could've performed an overnight FC loss test before increasing your CYA to confirm in case you had to SLAM. But now ..... :brickwall:

More than likely you'll need to SLAM. But to be sure, you could perform an overnight chlorine loss test: Pool School - Perform the Overnight FC Loss Test (OCLT) If you fail the OCLT, then you know for sure you need to SLAM.
 
Ah ok, so not dirt....

Just in case it was algae, I did chuck in 2 gallons of bleach , raising it to 20ppm .... before I added CYA.

Did not think of doing the OFCL .....Dah ! I have done the test at least 20 times before....should have thought of that.

However, as I have done it so many times I am pretty good at knowing usual or unusual FC loss.

I raised it to then let it drop naturally with SWG off, and it took a 6ppm hit day 1, but then levelled out to normal, so hopefully I managed to kill it off.

Is it possible to kill it off and then the stuff I am brushing is just dead/ or will die as I maintain FC at 9 for the next few days ?

thx
 
Likely to be mustard algae. OCLT should help confirm.

Mustard can be persistent and can go through a sand filter.

If a SLAM is indicated, be extra vigilant on the chlorine to eradicate it completely.

If it has color, it's probably alive. Full SLAM levels are needed.
 
Just took end-of-day reading now pump is off, FC is up from 9 to 11 since yesterday. Very odd, as I never see FC go up with Algae , just down. In fact my first warning sign is always that SWG is not maintaining FC - it is always either a drop in CYA or algae. Been algae free for 2 years.... so maybe I am due. I just brushed again and got the dust again, only in certain places and just a small amount. Would the FC not drop, if it is fighting algae?
 
So, Just got back from a work trip, brushed the floor and a plume of great dust came up....so guess I must have algae. I can actually see a green tinge to my water (it is normally crystal blue, to the point where people actually mention it ). Bummer that my CYA is ay 90 right now. Is it worth flooding my pool with the hose to bring the CYA down before slam?

Really odd though that my FC has held a 9 the whole time, the algae is not consuming any of it....odd.
 
So, Just got back from a work trip, brushed the floor and a plume of great dust came up....so guess I must have algae. I can actually see a green tinge to my water (it is normally crystal blue, to the point where people actually mention it ). Bummer that my CYA is ay 90 right now. Is it worth flooding my pool with the hose to bring the CYA down before slam?

Really odd though that my FC has held a 9 the whole time, the algae is not consuming any of it....odd.

- - - Updated - - -

Pic: pool algae.jpg
 

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Do you know the FC level needed at 90 CYA ? Is it worth me diluting the water to drop CYA? I can always buy more.

I do not know how to drain my pool, but I can just flood it with a hose , it should keep draining somewhere as it self levels if I over fill it sometimes.
 
Simon,

If water costs are not too high where you live, I would drain 50% of the water. This can be done using a sump pump or you can do it with a siphon hose. Put one end of the hose in your pool and the other end lower than the pool. Suck on the low end to get the water going...

Jim R.
 
Ok, I found a valve on my pool pipes by the pump that you can screw a garden hose onto. When I open it, water pours out, so I presume I can attached a hose and bleed from there? Question: should I keep the pump running to push the water through the hose? thx
 
Ok, dropped the water a couple of times and refilled, CYA was 80 when I started. Put in 4 gallons of bleach yesterday to raise FC to 31 , swept twice and got a LOT of green dust, could even see sweep makes left behind by brush. Today, I swept again and got tiny amount, but not much, FC only dropped 5 ppm, so added one more gallon. Cleaned filter, it basically ran with green water until fully clean and running clear. Swept 3 more times today, with almost no green dust now. Will leave pump running but swg off while I go on a trip from Monday, it should all be fine now. Will do an overnight test on Friday when I am back (absolutely no point ever trying to do the overnight test with FC over 25 as the margin for error when testing is WAY greater than the accuracy needed to determine less than .5 loss)
 
simonoaks said:
Ok, dropped the water a couple of times and refilled, CYA was 80 when I started. Put in 4 gallons of bleach yesterday to raise FC to 31 , swept twice and got a LOT of green dust, could even see sweep makes left behind by brush. Today, I swept again and got tiny amount, but not much, FC only dropped 5 ppm, so added one more gallon. Cleaned filter, it basically ran with green water until fully clean and running clear. Swept 3 more times today, with almost no green dust now. Will leave pump running but swg off while I go on a trip from Monday, it should all be fine now. Will do an overnight test on Friday when I am back (absolutely no point ever trying to do the overnight test with FC over 25 as the margin for error when testing is WAY greater than the accuracy needed to determine less than .5 loss)
Click to expand...
Your SLAM is not complete until:
1) The water is clear of all algae (sounds like you still have visible algae)
2) CC is 0.5ppm or less
3) Your overnight FC loss is less than 1.0ppm (pass an OCLT).

What is your current CYA & CC reading?

There is no harm in running the SWG while you are away to help maintain SLAM FC level.
 
tested pool again at 10.30 this morning (since 4pm yesterday ) it is at 30ppm. CYA is 75 /80 .

Brushed twice today, and also cleaned filter again (from the overnight running) it had SOME green but very little and washed away easily.

I know I need to pass the overnight, but I have SLAMed enough times to have a really good sense of the FC drops and when it flattens out. I want to leave the SWG off while I am away so the FC can drop naturally, to a low enough level for the kids to be able to swim at the weekend. Will take another reading in an hour to see the drop today. Just a big waste of test supplies to keep testing at 28+. I presume even while the FC is dropping a bit, it will still kill the algae at FC 22+ , right ?
 

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