Pool Balance Issues Pt II

[Rexyboy]

I wanted to start a new thread for the next stage of getting my pool into shape. In the first step I successfully shocked my pool which took a bit over a week to go from dark green to clear blue. The thread for interest is here help-pool-balance-issues-t54770.html

This morning I completed a full set of tests with the following results:

FC 7.5
CC 0.5
TC 8
pH 7.5
TA 120
CH 180
CYA 25
Salt 5430ppm

The things I see need attending to are:

1. High TA needs dropping (acid and aeration)
2. Low CYA (salt water pool)
3. Black spot (currently brushing regularly with SS brush, longer term issue)

What is your advice on where to get started?

Thanks.

 

[marty]

Try rubbing a puck on the black spot.

 

[Rexyboy]

Sorry i'm new to this.... A "puck" is a chlorine tablet that looks like a hockey puck? How does this work, does it give a high dose of chlorine to the black algae killing it? How often do I apply, do I scrub in between times?

Appreciate the help.

 

[PiratesLoveBacon]

Liquid chlorine/bleach + spray bottle = no more black spots at or above the water line.

 

[UnderWaterVanya]

Sorry i'm new to this.... A "puck" is a chlorine tablet that looks like a hockey puck? How does this work, does it give a high dose of chlorine to the black algae killing it? How often do I apply, do I scrub in between times?

Appreciate the help.

Yes. Trichlor our calhypo are available in 3" pucks/tablets. 1" trichlor are also available, not sure if calhypo comes that way.

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[Richard320]

Sorry i'm new to this.... A "puck" is a chlorine tablet that looks like a hockey puck? How does this work, does it give a high dose of chlorine to the black algae killing it? How often do I apply, do I scrub in between times?

Appreciate the help.

Yes, that is a puck. You might be able to find one single-wrapped in a bin on the counter at the pool store. Or ask any neighbors who have non-SWG pools. They probably have a bucket of them. They are slow-dissolving Chlorine, and by setting it on the stain, it will bleach it out by keeping the FC in that area extremely high.

TA will come down all by itself if you just keep pH adjusted consistently. The aeration process only speeds it up.

Your CYA is too low for a SWG pool. You can wait a little bit until the black spots are gone and you're sure the algae is all gone to raise it.

 

[JasonLion]

Have you checked to see if the black spot is a metal stain or if it is algae? Metal stains are generally smooth and won't scrape off, while algae will feel slimy and a small sample scraped off with a finger nail will stain paper green. The treatments are very different for metal stains and for algae spots.

 

[duraleigh]

Double what JasonLion just posted. Identify the stain positively before attempting the cure. Got any pics?

 

[Rexyboy]

The spots are very dark green and slimey which look black from the surface. Each spot is about 1/2" in diameter (or smaller) and they appear in clusters. They appear mostly in the shaded corners of the pool transitions and steps. You can scratch them with your finger nail and it leave a green slimey muck on your nail. I am pretty sure they are algae. I have continued to scrub with a SS brush which lightens the colour. I have not yet had the chance to rub the puck on them but I understand the idea.

 

[y_not]

That sounds exactly like algae to me. Didn't you just get done shocking your pool in your other thread?
Either way you need to start the shock process to get rid of it. If you have already shocked, you should have kept going until those spots disappeared.
That is unless they are above the water line, but it doesn't sound like it.

 

[duraleigh]

Using the shock process to eliminate black algae (your description makes me convinced you have identified it correctly) may use up an awful lot of chlorine......although it will certainly work.

What I would suggest alternatively is that you maintain your FC at about twice the normal level (so around 5-7 ppm with a pool of CYA 25) and then let that be your new "normal" until you can eliminate the black spot.

There is no quick, easy fix. Your best path is going to be to brush each spot daily (or twice daily, if you have time) with a stainless steel brush.

This will scrape off the top surface of the black algae and expose it to the elevated chlorine.

This procedure will take you WEEKS probably to kill it all but you can use your pool the entire time. You just have to be persistent until it is ALL gone.

If you have already boosted your CYA, consult the FC/CYA chart in Pool School to determine what your new FC level should be.

 

[UnderWaterVanya]

Academic question: what happens if you get black spot in a vinyl pool? Brushing with a steel brush is not an option.

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[Bama Rambler]

Vinyl pools almost never get black algae. Black spots on a vinyl pool are almost always staining of some sort so brushing wouldn't help anyway.

 

[UnderWaterVanya]

Vinyl pools almost never get black algae. Black spots on a vinyl pool are almost always staining of some sort so brushing wouldn't help anyway.

Thanks

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[y_not]

Using the shock process to eliminate black algae (your description makes me convinced you have identified it correctly) may use up an awful lot of chlorine......although it will certainly work.

I thought that black algae was fuzzy and scaly, like lichen on a tree or a sidewalk. Hence the roots.
At least that's what I have seen it as.

The spots are very dark green and slimy which look black from the surface. ..... You can scratch them with your finger nail and it'll leave a green slimy muck on your nail.

Is he not describing just an particularly CL resistant algae scum buildup of some sort?
Or is this a type of "black algae" that I haven't seen before, or described here at TFP in any case?

Thanks duraleigh.
Always ready to learn more.

 

[y_not]

Vinyl pools almost never get black algae. Black spots on a vinyl pool are almost always staining of some sort so brushing wouldn't help anyway.

Why don't vinyl pools get black algae? I have always wondered why I have never seen the stuff in a vinyl pool.
Is it because it's far, far less porous, so it can't build up in the pores and take root?

 

[Bama Rambler]

It's not only less porous but the chems in the liner help resist it somewhat.

If you scrape off the head of a black algae node the insides are green.