Having problems with high CYA

Chlorinating, maintaining the right chlorine levels,
chlorine problems. Dichlor, trichlor, cal hypo, bleach,
granules, chlorine pucks and chlorine sticks.
Shuggie
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Location: Menorca

Having problems with high CYA

Postby Shuggie » Sun 08 May, 2022 03:44

New to the forum and I’m here out of desperation after problems with high CYA problems.

I’ve had a good search of the internet and this forum and have read a good bit about CYA and the problems it can cause to chlorine levels. So I have a basic understanding.

So a little bit about the pool…

10m x 5m in ground

72500 litres / 19200 gallons

72m3

Sand filter

Historically Triclor pucks have been used to sanitise.

I’m in Menorca, Spain

The source of water for the pool is from a neighbours well.

That comes in to my property at PH - 7.7, Alkalinity 171

I’ve been maintain the pool myself for the last 2 years and have always struggled keeping a decent free chlorine level and have had algae problems during the peak of summer. Until this year I was only testing for free chlorine and PH as that was the advice I was given, wrong I know. I’ve now bought a Pool Lab 1.0 water tester and that’s when I discovered the high CYA. First test was Over Range for the machine so CYA was in excess of 160ppm. I understand the only way to get rid of the CYA is to drain and refill. I’ve been doing this for the last 2 weeks by vacuuming to waste and backwashing on a daily basis and then refilling by hose. I’ve managed to get the CYA down 110ppm but realise I’ve got a long way to go to get it in the 30 to 50 range.

My local pool store said I should continue to use trichlor pucks to maintain sanitation. That didn’t make much sense to me as I’m just adding more CYA, but they are the experts so I continued doing that. They also advise to use a product called Actibon Shock by Piscimar which apparently helps to mitigate some of the effects of high CYA, it hasn’t.

So 4 days ago, with the CYA level not falling as quickly as I wanted, I stopped using trichlor pucks. Just didn’t make sense adding CYA when I’m draining so much water to get the level down.

I’ve done some research on using liquid chlorine/hipoclorito sodico. I’ve bought 25litres drum which has active ingredients of 10.35% or 120 g per litre. Cost about €30. I’m not sure how much to use though to get my chlorine up again.

From my research I’ve come to the conclusion that using trichlor pucks is just going to progressively increase the CYA level over time. This is exactly what has happened to my pool.

So my plan is to keep draining and refilling the pool until CYA drops to 30-50ppm. This seems to be a slow process in dropping the CYA and I’m debating draining on a large scale and getting a water tanker in to refill. It won’t be easy dispersing that amount to water in a one go though. What do you think?

I’ll use liquid chlorine to sanitise in the meantime. Is this a good option for full time sanitation?

My pool readings this morning are:

PH - 7.71 (probably due to constant refilling with well water that’s 7.7)

TA - 200+

FCL - 0.08 (Trichlor tablets removed 4 days ago)

TC - 0.28

CYA - 110

Thanks in advanced for any advice.


Teapot1
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Re: Having problems with high CYA

Postby Teapot1 » Sun 08 May, 2022 09:14

What is the pool, vinyl liner, tiled?
Now back to your local pool shop, they are talking cobblers! Nothing new there most do, they have very little understanding of how pool chemistry works.
Yes keep using liquid, my advice would me a bit more than normal as you can slowly oxidise the CYA to reduce it over a season. Did this in France as to empty was impossible as it ran down the high street! I ran very high chlorine when no guests were in and just moderately high and we got the CYA down to a manageable level. As it comes down youll gain more control no need for another silly product the pool shop recommend. Just keep your free chlorine around 7.5-10% of the CYA level.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
Teapot1
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Re: Having problems with high CYA

Postby Teapot1 » Sun 08 May, 2022 09:16

Add roughly 750ml of chlorine should give you 1ppm so worth a test to see how fresh it is.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
Shuggie
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Posts: 11
Joined: Sat 07 May, 2022 03:22
My Pool: In ground pool, 10m x 5m, 72500 litres, pump: Astral Victoria Plus 38771. Sand filter. Mosaic tiles. Water is from private well.
Location: Menorca

Re: Having problems with high CYA

Postby Shuggie » Sun 08 May, 2022 10:01

Thanks for the reply Teapot1.

I think I understand you, does it work out like this.

7.5% to 10% of my CYA (110 at the moment) works out at FC level of 8.25ppm to 11ppm.

With the app I have downloaded, as recommended on this site, that would mean I need to add 5.6l to 7.5l of liquid chlorine based on chlorine strength of 10.35% to achieve 8.25 to 11ppm.

Is that correct?

What would you recommend adding on a daily basis to maintain these levels? And will the pool be safe to use?

I have now dropped my PH to 7.26 and TA to 156. Pool is starting to get a green tinge to it so looking to get liquid chlorine in it tonight.
Denniswiseman
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Re: Having problems with high CYA

Postby Denniswiseman » Sun 08 May, 2022 16:12

Excessive CYA renders your chlorine ineffective and you have to use more to get the same sanitation
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm
To reduce your CYA you have to do a partial drain and refill
Continuous use of Trichlor/Dichlor will raise your CYA which means you have to raise your chlorine level as well

If you are about 110 then drain 50% to get to 55

Use these common products to balance your pool
Liquid chlorine (sodium hypochlorite or plain bleach) Liquid chlorine only adds salt
Muriatic acid (hydrochloric acid) to lower pH and TA
Bicarbonate of soda to raise TA
Aeration will raise pH only
Soda ash will raise pH and TA

Pool Maths will help you work out what to adjust to get to your correct levels
Shuggie
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Posts: 11
Joined: Sat 07 May, 2022 03:22
My Pool: In ground pool, 10m x 5m, 72500 litres, pump: Astral Victoria Plus 38771. Sand filter. Mosaic tiles. Water is from private well.
Location: Menorca

Re: Having problems with high CYA

Postby Shuggie » Mon 09 May, 2022 02:58

Thanks Denniswiseman for your reply, I’ve read your theory in a few other posts on this forum.

7pm yesterday evening I add 8 litres of liquid chlorine (10.35%), with an aim of trying to get my FC to at least 8ppm.

This morning my readings are:

FC - 0.44

TC - 2.04

PH - 7.49

Alk - 162

CYA - 100

Am I correct in thinking that my FC level is low as most is now CC ?

Do I need to do a Slam/shock to get rid of the CC?

Is that worth doing at the moment with the CYA still high at 100ppm? What is an acceptable level of CYA to do a Slam/shock?

The first time I measured CYA was on 24/4 (16 days ago) and it was 158 now it’s 100. So I’m managing to lower it by 3.6ppm a day. I’m going to go for it today and drain more water than I’ve done on previous days and really try to get this CYA level down.

Please keep the advise coming, much appreciated and needed.
Teapot1
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Re: Having problems with high CYA

Postby Teapot1 » Mon 09 May, 2022 11:39

Yes you should shock the pool and keep the level up until your TC is 0.5 or less. 40% of your CYA fig is a shock level to go for.
What is the pool, tiled etc or vinyl lined/grp?

If you are going for a drain/refill add your chlorine afterwards save wasting, you probably already do but just in case.

Your test meter measures turbidity for CYA as your water gets clearer the CYA figure usually improves because of the higher clarity.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
Shuggie
Pool Enthusiast
Pool Enthusiast
Posts: 11
Joined: Sat 07 May, 2022 03:22
My Pool: In ground pool, 10m x 5m, 72500 litres, pump: Astral Victoria Plus 38771. Sand filter. Mosaic tiles. Water is from private well.
Location: Menorca

Re: Having problems with high CYA

Postby Shuggie » Mon 09 May, 2022 11:44

My pool is mosaic tiled.

I think I need to keep lowering the CYA before I attempt to shock, would you agree?
Teapot1
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Re: Having problems with high CYA

Postby Teapot1 » Mon 09 May, 2022 11:45

Yes completely, sorry my edit probably crossed with your post.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
Denniswiseman
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Re: Having problems with high CYA

Postby Denniswiseman » Mon 09 May, 2022 11:46

Shuggie
Pool Enthusiast
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Posts: 11
Joined: Sat 07 May, 2022 03:22
My Pool: In ground pool, 10m x 5m, 72500 litres, pump: Astral Victoria Plus 38771. Sand filter. Mosaic tiles. Water is from private well.
Location: Menorca

Re: Having problems with high CYA

Postby Shuggie » Wed 18 May, 2022 05:50

I started my Slam on Monday evening and I think I might be coming to an end, what do you think?

This morning just before sunrise my readings were:

CYA - 67

FC - 38.88

CC - 1.26

I’ve just tested again at midday

CYA - 67

FC - 38.82

CC - 0.96

I hope by this evening I’ll have my CC down to below 0.5. The pool is absolutely crystal clear and I’ve been brushing it like mad.

This is my plan, am I correct?

1. Keep the filter running (I’ve backwashed twice since the start) until tomorrow morning.

2. Do an overnight chlorine loss test.

If they pass the CC of 0.5ppm test and the overnight chlorine loss test, I’m done, I presume?

3. I’ll then maintain a chlorine level (with liquid chlorine) of between 5 and 10 based on my current CYA of 67. Hopefully this CYA will continue to reduce through the summer.

My PH is currently running high at 8.04 and my TA is over 200. Should I wait until the Slam is complete before I start to adjust these? When I started the Slam PH was at 7.3.

I do seem to be having a problem keeping my TA down as my well water is coming into the pool at 171ppm and PH at 7.7. Can anyone give any advice on how to manage this effectively on an ongoing basis? What would be an acceptable TA? I’ve managed to get my PH down to 7.2 before but my TA has always been more than 150. Is that OK ?

I’m so excited to finally be getting to top of the nightmare (algae pool, high CYA) situation I’ve had for the last 2 years.

Please provide any advice you can.
Denniswiseman
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Posts: 2313
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
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Re: Having problems with high CYA

Postby Denniswiseman » Wed 18 May, 2022 06:04

You are well on your way
Try to reduce your CYA some more and let your FC come down
Finish your slam and then adjust
Chlorine / CYA Chart and
Recommended Pool Levels
Pool Maths
Reduce high total alkalinity

Use these common products to balance your pool
Liquid chlorine (sodium hypochlorite or plain bleach) Liquid chlorine only adds salt
Muriatic acid (hydrochloric acid) to lower pH and TA
Bicarbonate of soda to raise TA
Aeration will raise pH only
Soda ash will raise pH and TA

Excessive CYA renders your chlorine ineffective and you have to use more to get the same sanitation
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm
To reduce your CYA you have to do a partial drain and refill
Continuous use of Trichlor/Dichlor will raise your CYA which means you have to raise your chlorine level as well
Teapot1
Swimming Pool Superstar
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Posts: 387
Joined: Thu 29 Apr, 2021 00:43
My Pool: 12000 gallons vinyl liner,

Re: Having problems with high CYA

Postby Teapot1 » Wed 18 May, 2022 08:39

The high clorine level will give you a high pH level but dont worry, as the chlorine level reduces so will the pH so just wait. It is quite likely you will show a slightly higher combined chlorine during shocking as the chlorine will try to oxidise anything it can, in this case could also be oxidising CYA. As the level reduces so will the combined chlorine so should be ok. Lowering TA can be done but if your pH stays relatively stable not too much to worry over. Often with a TA of 100+ the pH rises quickly with any activity.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
Denniswiseman
Pool Industry Leader
Pool Industry Leader
Posts: 2313
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Having problems with high CYA

Postby Denniswiseman » Wed 18 May, 2022 12:07

RonPace
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Re: Having problems with high CYA

Postby RonPace » Thu 19 May, 2022 15:15

I am following this thread out of interest as I am sure one day it will happen to me...

But, am I reading this correctly - adding loads of liquid chlorine (bleach) oxides the CYA? I always thought it was impossible to get rid of the stuff except by draining and diluting... this then, to me, implies that if CYA starts creeping up, tell everyone not to use the pool for a while and bung in 10 litres of bleach... yes? no?

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