FC holding, still have algae

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Sluggo33x

0
Jan 8, 2018
47
Sydney
I did a SLAM last week as I had some light algae (see calcium levels thread), and it all cleared up nicely and my FC level is holding overnight but I've noticed what appears to be algae again on the grout lines. Won't brush off with the pool brush, but comes off with a sponge.

Is it possible to have algae with FC levels holding? Last FC test showed 17.5

I'm assuming it's algae, I have no trees or other litter falling into the pool.
 
Algae can create biofolms that protect it from the chlorine. You need to brush to disturb the algae.

Odd that the brush does not take it off but a sponge does.
 
Your other thread got a bit sidetracked, so I'm glad you started a new one :)

Algae sometimes take a few hours to die when it's established on grout. Is it below the water line? If so, then a little more time at shock level might be helpful.

I see some above the waterline sometimes where the chlorine isn't there to stop it, especially in this vicious humidity. I go around with a washcloth every few days when I'm in the pool.
 
Might need some more regular brushing on the tiles to help get rid of it, but it also sounds like your sponge method is working well. So what is your CYA level again? Is it convenient to keep it at shock level until the green is annihilated?
 
Here's a pic of what I'm talking about. Pool brush won't remove it, but a good scrub with a kitchen scourer gets most of it.
9e454f0d5f28e4070daacd865bbd773a.jpg
 
Pool brush won't remove it, but a good scrub with a kitchen scourer gets most of it.
Click to expand...
That is odd. :confused: Aside from the brushes being steel or nylon, I wonder if the pool brush, if it's the wider type most people use, simply passes over the grout as opposed to doing it by hand with a smaller brush that allows more pinpoint accuracy and pressure. Hummm.

Also wondering if that area in the pic is in the shade? If so, is it restricted to just that area, or is the staining across the entire pool?
 
It's a regular wide pool brush. Might see if the local shop has a different brush, although the bristles should be making contact with the grout.

Would a stainless steel algae brush like this be ok on my mosaic tiles?

Hy-Clor Pool Algae Brush | Bunnings Warehouse

The whole pool get sun after lunch. Same staining is visible across the pool, not everywhere though.

Does it look like algae, or something else? Strange that my FC held with the overnight test.
 
After you scrub it with the scourer, does it disappear a few hours later, but then come back? Or do the clean spots that have died out remain dead?

To answer your earlier question, one type of algae - black algae which is actually a bacteria - can remain alive for quite a while after a SLAM with zero overnight chlorine loss. The trouble with black algae is that it re-forms it's protective layer very quickly. If it is, it's great that you're on top of it now!
Pool School - Black Algae
 

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The SS brush will eventually leave scratches on glazed tile, but used sparingly might be OK. You could get one and try it in an inconspicuous small spot for a couple weeks first and then decide. A narrower nylon brush would create more pressure and get into the grout lines better.

There are combo brushes that I haven't been able to find here (let me know if you do!). A mixed nylon/SS brush might be a good compromise, but I'd still try it on an inconspicuous spot first.
 
The cleaned areas seem to come back again after a while. I've been staring at the tiles for so long, I think my eyes are starting to play tricks on me.

Whatever it is, it's definitely got a green tinge to it.

Just did a full test on the middle of a sunny day.

FC 19
CC 0
CYA 50
TA 100
CH 325
SALT 5,000
pH Didn't test as FC>10
 
A SLAMin' you will go!

Yeh, I don't blame you for the eyes going wonky.

I would get the smallest container of trichlor pucks/tablets (75 mm (3") diameter, 5 x 200g tablets). Brush a couple of spots, and put a tablet on each one, but remove it after 10 minutes and brush it again. Leave the tablet off for 10 minutes, swish water across it a bit. Try the tablet again for another 10 minutes. See if that wipes out the spots, or lightens them, and let us know.

Also get some plain vitamin C tablets (not chewable or anything, preferably plain, white tablets). Crush up 20 or 30 tablets and put the powder in an old sock. Hold that against a spot for a couple minutes and see if there's any difference compared to the treatment above.

(Hoping Pat comes back as well, I'd like his take on that thought)
 
needsajet said:
A SLAMin' you will go!

Yeh, I don't blame you for the eyes going wonky.

I would get the smallest container of trichlor pucks/tablets (75 mm (3") diameter, 5 x 200g tablets). Brush a couple of spots, and put a tablet on each one, but remove it after 10 minutes and brush it again. Leave the tablet off for 10 minutes, swish water across it a bit. Try the tablet again for another 10 minutes. See if that wipes out the spots, or lightens them, and let us know.

Also get some plain vitamin C tablets (not chewable or anything, preferably plain, white tablets). Crush up 20 or 30 tablets and put the powder in an old sock. Hold that against a spot for a couple minutes and see if there's any difference compared to the treatment above.

(Hoping Pat comes back as well, I'd like his take on that thought)
Click to expand...
Will give the tablets a go today and report back.

Most important question, is it still ok for the kids to swim at current levels and with possibly some algae?
 
Yep, for sure.

Our safe swimming rules are:
1. Clear to the bottom so you can see everyone
2. pH from 7.2 to 7.8
3. FC at or above minimum and at or below shock level for your CYA, per [FC/CYA][/FC/CYA]

Algae is not a health hazard (there are rare circumstances and species of algae that are bad, but not relevant to maintained swimming pools)

And FC at shock level for CYA level has less active chlorine (hypochlorous acid and hypochlorite ion) than a commercial indoor pool at 1 ppm and no CYA.

In fact, one of the tenets of TFPC is to keep the pool open at all times to maximise the swim season.
 
Seeing as you have passed a SLAM previously, to include the OCLT, I'm inclined to think it's either a root-based algae or residual staining. If you were able to see a change with a tablet/puck, it would confirm that it's organic. Seeing as how your CYA is 50 and the SLAM for that is 20, you could run an OCLT one more time this evening. I suspect it will pass, but you never know. Once you confirm the passing of the OCLT, I would consider increasing your FC for the next 24 hours to your Mustard Algae level which is "29". Do that only for 24 hrs though. After that, I would allow the FC to fall about mid-way from your normal SLAM level, so about 10 or so and see if you can keep it elevated that way for a few days. At the same time, continue scrubbing those grout lines with a narrow brush as to not damage your tile. At my local store, I can get those small/narrow brushes in steel, brass, or nylon, so you should be able to find them locally as well. Scrub carefully there as well though so that you don't damage the actual grout. I suspect that you're left with an aggressive root-based organic material that requires manual agitation to break it down and penetrate it at the root level. If you were lucky enough that it's only a stain, it could still take a while as stains can be quite difficult to remove as well. But that would be my course of action if it were my pool. Perhaps you might receive more input to compare with, but either way I'm curious to see how things go for you.

PS ~ Everyone can swim up to SLAM level (20). If you run it above to the MA level of 29 for 24 hrs, everyone will have to wait. But once it drops back down to 20 or below you're fine. Give everyone a brush and make it a scrub party. :)
 
I do make the kids get out and count to 200 if I have to pour acid in. While they're counting, I brush the floor under the return where I poured the acid in, to be on the safe side, and because they count very loud and very fast!

- - - Updated - - -

A scrub party sounds like a great idea! :)
 
OK, did the puck test on a few spots and after 10 minutes the grout is white without the need for any scrubbing, so I guess I need to SLAM again.

Strange as FC held with the overnight test and has been fairly stable. There's a slight chance that my CYA test results are incorrect as I received an email from the shop where I purchased saying that they've detected some issues in recent batches and a replacement reagent is on its way.

Let's assume my CYA of 50 is correct, is that high enough for A SLAM?

Also, does it matter if I bump the FC above the shock level or does it need to be spot on?

Should be noted that the water is crystal clear, and I've had the cover off for a week.
 
Yes, anything over 30 ppm CYA is fine for a SLAM, and that's only because it's possible to measure it at 30 ppm and up, so you'll know the FC level to use.

There's quite a bit of latitude on the shock number if above the shock level in [FC/CYA][/FC/CYA]. For example, the mustard algae level is about 50% higher, but as Pat mentioned we won't suggest here on TFP that you swim in it at that level. (though undoubtedly some of us have).

I think Pat's right. The best treatment is probably to brush those areas really well, and if there's no swimming happening, go ahead and use the mustard algae shock level for 24 hours.

Glad to hear the water is still sparkling nicely :)
 
Up to mustard levels we go, thanks for all the help


Question re type of chlorine I'm using for the pool math calculator. I have the regular 15L blue drum that all the pool shops supply, and it says active constitute is sodium hypochlorite.

So what do I select from the sanitizer type in the calculator?
 

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