Above ground pool, white/grey sediment on bottom

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I

Irate pool owner

Member
Jun 19, 2022
5
London
Hello!
I have an above ground pool, holds 10.5k litres.
I’m in a hard water area in London .
I filled the pool up 3 days ago, chlorine levels and ph is fine. I shocked pool on evening 1 to get some chlorine into it.
There are already some wispy lines of grey/white sediment on the bottom that disappear into the water when I try to remove them with the net.
I had this last year as well and could not solve it. Eventually the pool goes super cloudy and I can’t recover it.
Any ideas? I’m guessing it must be calcium? If so how do I fix it?
 
I had a water test done at a pool shop on Saturday, have copied it here:

Phosphate 278 ppb
Iron 0 ppm
Copper 0 ppm
Cyanuric Acid 0 ppm
Alkalinity 87 ppm
Hardness 170 ppm
pH 6.5
Combined Chlorine 1.61 ppm
Total Chlorine 7.94 ppm
Free Chlorine 6.33 ppm

On the advice of the guy in the shop I put in some ph increaser.

Would there be dead algae already only after a few days of the water being in there, do they grow that quickly? Have looked again today and the grey wispy streaks on the bottom have definitely grown, so its something happening!
 
Yes, water can begin to grow algae very quickly in unchlorinated water. Test strips are often unreliable and do not give the ability ot test at specific numbers. Local store testing is often incorrect, or the advice provided also incorrect. However if your pH was indeed below 7.0, it was good to increase it. Are you able to order a Taylor K-2006C test kit where you live? That would be ideal.

Remember that new water has no stabilizer (CYA) so you definitely want a minimum CYA of 30.

Adding CYA:
To increase CYA via granular stabilizer, place the required amount as calculated by the Poolmath calculator into a white sock and place in the poolside skimmer basket. For those concerned about suction flow to the pump, suspending the sock near a return jet or from a floating device will also suffice. Best never to allow undissolved granules to rest directly against the pool surface. Squeeze the sock periodically to help it dissipate. Once dissolved, consider your CYA adjusted to that programmed (target) level. CYA test readings should show a rise in 24-48 hours, however some pools may experience a longer delay to fully register. Best to confirm final CYA in about 5-7 days before adding any more stabilizer/conditioner.
Click to expand...
 
Thank you for the advice !
I can get a Taylor kit here.
You recommend it?
Am happy to get one if I can just start to understand how to fix the issue as otherwise it’ll be filling and refilling all summer which is way more expensive than buying a test kit and some chemicals.
 
Which Taylor kit are you able to get? The K-2005 doesn't have the FAS-DPD testing but would be able to give tests for everything but FC. FC just happens to be the most important one, so if you can get the FAS-DPD separately (or in with the kit as a K-2006c) it would be best.

It sounds a lot like either algae or dust getting into the pool. Testing the FC accurately with the FAS-DPD test would let you do an Overnight Chlorine Loss Test which would tell you if it is algae and if you need to clear that out.
 
Yep, that has everything! The FAS-DPD reagents it comes with are going to be small, so you might want to see if you can source replacement reagents for that test, but that's the right kit.

Meanwhile brush/scrub all the pool surfaces you can, and add around 5ppm of chlorine daily. Can you get liquid chlorine from somewhere in the UK? (Also called liquid pool shock - it's basically concentrated bleach.)
 
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