Just taken over - Some advice - CYA, Blackspots, FC to TC ratio, Bromine?

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fijjitt

Member
Feb 8, 2025
18
Mallorca
Hello, Thanks to all for such a helpful Forum ;)
I've done a few searches on here and come to some conclusions.
Just taken over the pool.
It's spring here, there is sun every day. The pool has been running over winter but without swimmers.
There has been a weekly visit from a Pool Guy. I think just additions of all in one tabs for the winter.
There will be no immediate swimmers, but I'd like to use as soon as possible.

First I raised the alkalinity to to 80 and the ph is at 7.2 (both were very low)

my test strip shows
TH over 500
FC somewhere between 5 and 10
Bromine? quite high 6 or more (is this a false reading to to high chlorine levels?)
TC 10
CYA 100

There are black spots appearing on the tile grouting.

So I think I need to...
1 Reduce the CYA level to at most 60.
2 Shock the pool (and scrub) to kill the Blackspots.

Any advice appreciated..
- Will a chlorine shock reduce the CYA by any significant amount? or do i definitely need to replace some water?
- In the mean time; Should i just use liquid chlorine and keep the FC at least 8?

signal-2025-02-09-145702_003.jpegsignal-2025-02-09-145702_004.jpeg
 
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fijjitt said:
Hello, Thanks to all for such a helpful Forum ;)
I've done a few searches on here and come to some conclusions.
Just taken over the pool.
It's spring here, there is sun every day. The pool has been running over winter but without swimmers.
There has been a weekly visit from a Pool Guy. I think just additions of all in one tabs for the winter.
There will be no immediate swimmers, but I'd like to use as soon as possible.

First I raised the alkalinity to to 80 and the ph is at 7.2 (both were very low)

my test strip shows
TH over 500
FC somewhere between 5 and 10
Bromine? quite high 6 or more (is this a false reading to to high chlorine levels?)
TC 10
CYA 100

There are black spots appearing on the tile grouting.

So I think I need to...
1 Reduce the CYA level to at most 60.
2 Shock the pool (and scrub) to kill the Blackspots.

Any advice appreciated..
- Will a chlorine shock reduce the CYA by any significant amount? or do i definitely need to replace some water?
- In the mean time; Should i just use liquid chlorine and keep the FC at least 8?

View attachment 627530View attachment 627531
Click to expand...

I've got my eye on a Taylor kit.. Might have to wait a week or so :rolleyes:
Should I just ignore the high Bromine result? and wait to see how I get on with sorting the CYA and Chlorine balance first?
 
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F,

While having one of our recommended test kits keeps us all on the same page.. In your location that might, or might not, be something that is easy to do... :(

Some things you can do now...

1. You will have to drain about half your water to get your CYA down to 50 ppm.
2. You have a chlorine pool so disregard any Bromine reading..
3. Chlorine Tablets are the cause of most of your current problems.. They add CYA to the water.. the higher the CYA the higher you need to keep your FC.
4. Using tablets is ok, if you routinely test, so that you can keep your CYA in check.
5. Which Taylor test kit do you have your eyes on???
6. If you are going to "shock" what we call a SLAM, do it with Liquid chlorine.. Is this easy to get in your location??

Thanks,

Jim R.
 
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Hey, Such Quick replies, Amazing. :)
I've ordered the taylor k2006
But it's going to take a week to get here.
@Jimrahbe thanks - '2. You have a chlorine pool so disregard any Bromine reading'.. alleviates a whole world of problems :cool:
Do I need to address the black spots immediately? or should i address that when I'm replacing the water?
The water is about 12c
 
What kind of pool surface do you have?

Can you scrape out one of the black spots and smear it on a paper? We need to determine if it is black algae or some other type of stain.
 
fijjitt said:
It's a 'tiled' surface, the spots are appearing on the grout.
Click to expand...
Grout has the type of cracks that black algae likes to take root in.

Scrape some off and see if it smears green to confirm black algae.

www.troublefreepool.com

Black Algae

This guide provides a step by step procedure for eliminating black algae in your concrete or gunite pool. Read full post here.
www.troublefreepool.com www.troublefreepool.com
 
Hey, again, thanks for your replies ;)
I went to try and find a Taylor kit in a couple of local pool supply stores.
I was surprised they both only had a few basic liquid tests, for salt and chlorine and ph. but then only test strips for the other chemicals.
I wanted to buy a CYA test specifically, but nothing available.
@Katodude mentioned - wait until I get a recommended test kit. But I get ever so fijjitty if I think I could be doing something positive.😊
Due to the black spots appearing, can assume the test strips are somewhere close? showing 100 CYA.
It's going to be a week or so until I get the kit so I can do the SLAM.
I can't bear to just sit and look knowing it needs attention 🤨

Any harm in getting on with the water replacement? balance everything best i can, then wait a week (for the test kit) and then do the SLAM?
Until I can do the SLAM I figured just keep the FC at the higher recommended level with my new lower CYA, to prevent the spots spreading?

Thanks 😇
 

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Here is the problem with doing the water replacement. If you spots are black algae you will need to physically scrape them. Then you will need to dump the highest strength liquid chlorine on them. It might be easier to do when the water is low.

Number 1 rule here is know what you are dealing with before you treat it.
 
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F,

If this were my pool I'd drain the whole thing and then use liquid chlorine and a brush to attack all of the grout lines...

I'd mix the chlorine with water at about 10 to 1 ratio. I'd put it in a pump-up sprayer like you use for weed killer..

I'd try just one small section to see how well it works first.. Then I'd do a another section at a time, and rinse it off after an hour or so..

Then, after filling the pool back up, I'd start using the TFP pool care process. :goodjob:

Thanks,

Jim R.
 
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Will do, started draining.

So what gives?
I went to the 2 main pool shops in my area, cash in hand, all i wanted is some chlorine and CYA.
Neither of them had CYA in any form.
was advised to be very careful using it as it can ruin your pool (I know 😂)
"Just use the tabs." seems to be the advice.

OK, Amazon, you win, Bugger.
25quid and at my door, 😋
 
fijjitt said:
was advised to be very careful using
Click to expand...
My 5 year pool store kid assured me I could wait the couple of weeks until they got more because, you see, when some burns off, there is still some left to protect the chlorine.

'You just built my pool and we filled it today'

*blank stare*

'Fill water has no CYA. I don't have 'any left', I have none'

*blank stare*

*light bulb*

'Well. Um. You can't know that until we test the water'
 
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fijjitt said:
, i was told to fill and test the water before worrying about cya.
Click to expand...
The current level needs to be tested reliably to see how much you should drain/exchange. You should overshoot a little because subsequent drains if you fall short also remove 'good water' Then it should be confirmed afterwards with another reliable test.

I had only fill water and knew my CYA was 0. :)
 
Why did I offer to look after the pool? lol
But if a job's worth doing..
I've recommended we don't refill the pool.
The grouting is pretty much missing.

This all started because I thought i'd offer to keep an eye on the ph and Chlorine.
Then I learn about alkalinity, oops adjust.
Then I learn about CYA, wow, ok, oops, let's adjust.
Then I learn about Black mouldy bits, Ah.
Then when I sat in the bottom of the empty pool, I learned all about grouting.

I thought I'd add some ph+, bit O' chlorine and jump right on in. :cool:

😢


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