FC holding, still have algae

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It's usually 12.5%, but should have a label saying 125 "g/L" or "grams per litre" sodium hypochlorite.

I recently got some 13% (Pool and Spa Warehouse), but the 125 is the most common by far.

Select 'bleach' in the sanitiser type. Plain bleach and pool chlorinating liquid are the same thing, except that we don't seem to have the powerful bleach they can buy overseas.
 
needsajet said:
No worries mate happy to help. Hopefully those spots will go quickly then it's smooth sailing. I envy that tiled pool and bet it looks great!
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Here you go, gratuitous self shot... Nothing fancy, more of a plunge pool.

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Based on my lunchtime reading of FC at 19 and target shock level of 29 (mustard algae), pool math (using the mobile app) told me to add 4.9L of chlorine, so I added approx 4.5L

My reading is now 36ppm.

I was mucking around with the trichlor pucks for about 45 minutes testing small patches of tile. Could they have added enough chlorine in that time to push it up?

Or, I just redid pool math and changed the bleach percentage from 6% to 12% (didn't realise it was 6% earlier), and it tells me I needed 2.5L

Did I get the percentage wrong the first time?

No damage done with the extra chlorine?
 
Sorry I was glued to the tennis! Yeh, it's not that harmful. It really just wastes a couple litres of chlorine and will come down quickly tomorrow in the sun.

The trichlor wouldn't have added very much in that short time. The pucks should still look nearly as big as they were before the testing. Probably the percentage setting.

I plugged it in to Chem Geek's pool equations spreadsheet, and you have the same active chlorine (HOCl and OCl-) as a non-CYA pool at 2.5 ppm FC, so nothing to worry about.
 
Just an update, the SLAM continues and I haven't needed to add any more chlorine as I added a bit too much at the start. FC sitting at 23ppm this morning and I'll do the overnight test tonight.

Water is crystal clear and most of the green spots have cleared up. The sock on the skimmer basket has also been relatively clean. There are some spots where it appears that algae is still present but it could be my eyes posting tricks on me.

I also adjusted the return jets to point as far down as possible to try and get the deeper water circulating. Both jets were previously pointing up and creating ripples on the surface.
 
Good to hear about the progress. Thanks for the update :) I have a couple of small scrub brushes in my pool tending kit that I use in the corners under the coping. When I noticed them today I thought of your grout!
 

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Mods, feel free to move to the algae sub category as my saga continues. I'm quite confused and frustrated with what's wrong.

I've now done two successful slams starting on 22 January and then again on 27 January, but it appears the algae is back.

The last SLAM passed all three tests, and my FC held overnight only two nights ago. Furthermore, FC has consistently been above 10 and closer to SLAM levels since mid January, so not sure how the algae is back.

Water is crystal clear.

I will do another overnight test tonight, but suspect it will pass.

I'm assuming it's algae as it looks like a dirty grey/green stain on the white grout throughout about 50% of the pool floor. Walls have slight staining. It should be noted that the staining is fairly light.

I did the vitamin C test today (could only find the orange chewable type), and it didn't make a difference. Back to the chlorine puck test and it removes most of the stain.

Note again as before, a regular brush won't remove the stain.

Could it be something other than algae and the SLAM simply bleached the stain white to only return as FC starts to drift down?

Here's today's test results.

FC 11.5
CC 0
CYA 60(ish)
pH 7.8 (probably not reliable as FC>10)
TA 100
CH 300
SALT 4,800

Should I throw in some acid tonight to bring pH and TA down (my target is 7.5 & 75ppm) before doing anything else? Pool math suggests 1.2L to get down to 7.2 ready for a potential SLAM.
 
Looking back at everything from the past week or two, something that caught my eye today is that your CYA is closer to 60, when before I believe the SLAM was based on 50. Doesn't seem like much, but it does require a slightly higher SLAM level. So in the previous attempts, if the FC should've been higher, it could explain why you were seeing some progress, only to have the tile revert back to color changes right afterwards. I know the FC was elevated for 24 hrs to rule-out Mustard Algae, but that is only for 24hrs after a successful SLAM. I understand the OCLT passed more than once, but in some unusual cases, if algae has become root-based into the pores of gunite/grout, it can be very difficult to penetrate. The tabs changing those stains seems to confirm.

With a CYA of "60-ish", if there is any chance it is in the higher end of the 60s, I would round up to 70 for future SLAM attempts. Also, we haven't talked about it much, but assuming you've inspected every inch of the pool for potential algae hiding places (ladder, behind light in niche, under skimmer lid, etc), when was the last time you did a thorough sand deep cleaning? If it's been a while, you might consider looking at the TFP Deep Cleaning a Sand Filter. Perhaps something else is allowing that organic stuff to come back to life?? I'm looking at just about anything now.

Other than that, I have a feeling that organic stuff in the grout has its roots firmly in there and the ultimate remedy will be continued scrubbing and an elevated FC level, rounded-up to match the highest possible CYA in your water, and perhaps another MA level treatment based on that higher CYA.
 
OK, another successful overnight test with zero FC loss and zero CC detected. Something is not adding up.

To answer your last questions, I struggle doing the CYA test with any real confidence. I landed on 60ppm yesterday, but give myself a +/- 10ppm margin of error. Having said that the last SLAM I did I started off at FC at 36ppm which would cover a CYA of 70.

The pool is only 6 months old so haven't bothered with a sand filter deep clean, just a backwash before SLAM.

We have no ladders or any unusual hiding spots, it's a simple rectangular pool with three steps and a bench seat.

I added some acid this morning to get the pH down in readiness for a potential SLAM.

Standing a few metres back from the pool it looks spot on with no staining, it's only when you stand over it that the dirt/stains are visible.

I've contacted my pool builder regarding a few cracked tiles and hard white drip marks on the walls, so might ask them about the staining if they ever show up.
 
I've contacted my pool builder regarding a few cracked tiles and hard white drip marks on the walls, so might ask them about the staining if they ever show up.
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Good idea! While builders don't always have the same chemistry principles we do at TFP, they may have some local insight about that grout. Curious to see what they say.
 
If there's concerns about swimming in 28 ppm FC, which is safe as houses at 60/70 ppm CYA, keeping the FC level to yourself is the practical approach.

You can drop the FC level with thiosulphate, and then put it back up right away after. This is a tad complicated and has to be done right. Hence the practical approach.
 
Fresh tests this afternoon after adding acid this morning.

FC 9.5 (only a drop of 1ppm in 24 hours)
pH 7.3
TA 75

The staining doesn't appear to be getting any worse. If it were algae would it not get progressively worse and wouldn't I expect a bigger drop in FC?

I plan to put the roller cover back on and let the water warm up for a swim over the weekend. I'll also turn the SWG back on to maintain FC.

Apart from peeking under the cover each day until the weekend, I don't plan to add anything or SLAM at this stage.

Will monitor closely and chase the pool builder.

Thanks for all the help.
 

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