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Swimming pools 2018
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teapot



Joined: 23 Oct 2013
Posts: 804
Location: Loire valley

PostPosted: Fri Mar 09, 2018 12:28 pm    Post subject: Swimming pools 2018 Reply with quote

It is time to update some of the information on swimming pools, over the years I have tried with other pool technicians around the world to get to the bottom of some pressing pool questions. Some of those questions get researched and new data published. I am to pass this on to owners so they can better understand and look after their pools.


1. Chlorine is the best anti algae, it works faster and better than most other things.

2. Packaged tablets of chlorine (choc, multi action and Lent) are nearly always stabilised chlorine so the more you add the higher the stabiliser level goes.

3. Stabiliser AKA Cyanuric acid is more in control of your pool water than the pH is, people check the pH levels but donít check the stabiliser level. Most green and problematic pools are down to too higher level of stabiliser and you cant accurately check stabiliser with dip strips.

4. Stabiliser level once it gets too high needs to be brought down by emptying some water and replacing with fresh.

5. Hydrogen peroxide is a waste of money as it is a stronger oxidiser than chlorine (but a worse sanitiser) it burns out the chlorine in your pool so you cant get a chlorine reading until itís gone. It cost twice as much as chlorine so why not buy twice as much chlorine and look after your pool properly?

6. You can look after your pool very easily and cheaply just using Eau de javel (for a source of liquid chlorine) and acid (pH-) from a Brico store. If you need to increase the alkalinity (for a tiled or plaster finished pool) bicarbonate of soda from the super market, Most vinyl liner pools the alkalinity doesnít matter unless you have a specific problem like pH drifting so ask for specific information.

7. chocíng a pool is NOT about buying a product called choc, itís about raising the free chlorine to a level and holding that level until everything is oxidised out of the water (algae, chloramines etc) and you may need to hold this high level of chlorine for a few days. A one off dose of chlor choc pastilles is not going to achieve very much except raise the stabiliser level some more.

8. Anti algae unless itís copper based doesnít actually work if you have a green pool already, itís an industry con! More of your valuable chlorine is used up burning the anti algae out of the pool so making the situation worse!

That is a refresher from what I posted a few years back.
**Going back to point 3**, I said that; "Cyanuric acid is more in control of your pool water than the pH is, people check the pH levels but donít check the stabiliser level". (October 2016) This has now been proven to be correct.
Eye irritation is felt more when the pH is at 7 or below than when it goes higher up to pH9. Cyanuric acid (stabiliser) is used in outdoor pools, its reduces the rate at which the sunshine burns off the chlorine. The chemical binds to the chlorine and acts like a sun screen. What we now have is a compound that is far less dependent on the pH so there is very little difference in the sanitising ability of the chlorine from pH7 to pH9.

What we do know is the reduction in the sanitiser strength due to the bonding of cyanuric acid to the chlorine needs to be countered by an increase in the free chlorine amount. The old idea of free chlorine at 1-1.5ppm is not enough in most cases when you have 30-50ppm of stabiliser in the pool water. Certainly if you are having trouble with your pool increasing the chlorine level is necessary. You can help yourself by lowering available nutrient levels in the pool, (no food for algae, no algae) so using a phosphate remover can really help but increasing your chlorine level to 7.5% of the cyanuric acid level.
(CYA @ 30ppm x 7.5% = 2.25ppm chlorine)
(CYA 50ppm x 7.5% = 3.75ppm chlorine)
Whilst these levels are higher, the actual disinfection level is less than an indoor pool at 1ppm of chlorine and no cyanuric acid stabiliser. The fact that within pH 7 to pH9 there is barely any difference in chlorine's ability to sanitise means testing and tightly controlling the pH is far less important than testing for cyanuric acid stabiliser. Some areas have naturally hard water and high alkalinity, spending more time and money getting the level down to the previous recommended pool levels (pH 7.2-7.6), can now stop. If the higher pH is easier to maintain and doesn't cause undue eye irritation then all is good but you **must** maintain the chlorine level relative to the cyanuric acid stabiliser level.

**Going back to point 6;** For vinyl or fibreglass pools alkalinity is not as important as it is in tiled/plaster pools. The previous recommended alkalinity levels vary from 80ppm to 200ppm, however the higher the alkalinity figure the easier the pH will climb due to the loss of C02 from the water. The figure for alkalinity (bicarbonate of soda dissolved in water is a pH around 8.1-8.3) this is too high for pool use (pH 7.2-7.6) stay with me bearing in mind the previous CYA topic above and pH, I know. A customer in the Dordogne has really soft water with low hardness (vinyl pool) with alkalinity at 29ppm I said we must add bicarbonate of soda! (alkalinity +) but slept on it over night, decided nothing bad had happened in the last two seasons, so we left it and monitored. I carried out experiments on my pool (alkalinity 240ppm) and his (29ppm) using and aerating rig. The pH in my water sample climbed to 8.3 withing an hour of aeration. 48 hours of the low alkalinity sample (29ppm) showed and increase in the pH to 7.6 from 7.2. I prepared another sample with alkalinity set at 40ppm and repeated the same test with aeration and over 48 hours the pH reached 7.8. I double checked the original test with the samples at alkalinity at 29ppm and 240ppm and again the results were almost identical to the first. I spoke to a friend about this and they confirmed an alkalinity level of 20ppm means the water will balance out with a pH at 7.75 meaning no pH- would be required.

With low alkalinity the pH will reduce much quicker (less pH-) so if you have that kind of water be aware otherwise you can get into a situation the pool industry incorrectly labels pH bounce. Nothing bounces, for a give amount of pH- the pH reduces, if the pool is high on alkalinity then the pH will climb back up quickly, these are separate cases. My pool and others I have setup the same way with low alkalinity use far less pH- in a season than ever before (my pool less than 1 litre of acid) and the pH does not climb anywhere near as quickly, again making pools easier to look after. Water at 40ppm alkalinity still has around 7 times more C02 than the air above the pool so the C02 loss is slower than a pool with higher alkalinity that may have 20 times more C02 than the air. In short most pools are over carbonated (alkalinity) old tables on the web are more commonly for plaster/tiled pools which could use a higher alkalinity.

*aeration is the process that normally takes place in a pool causing the pH to rise. The test rig was built to examine this and accelerate the process but the findings are still correct.

Some flocculents will not work well with alkalinity below about 80ppm.

Anyone wishing to read further into the CYA/pH paper, the link is below.
http://www.poolhelp.com/wp-content/uploads/2017/11/Relative-Effects-of-pH-and-Cyanurate-on-Disinfection.pdf

Thanks also to Richard Falk and Kim Skinner for their help.
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e-richard



Joined: 17 Oct 2004
Posts: 4944
Location: Algarve, Portugal

PostPosted: Fri Mar 09, 2018 1:13 pm    Post subject: Reply with quote

Wow, teapot, that's a truly awesome and comprehensive description and I wish I understood 10% of it.



Fortunately, I have a poolman that I pay to do all that Wink
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teapot



Joined: 23 Oct 2013
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Location: Loire valley

PostPosted: Fri Mar 09, 2018 1:15 pm    Post subject: Reply with quote

Yes I am a man of few words Wink
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KathyG



Joined: 28 Jan 2006
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Location: Le Faou, Brittany

PostPosted: Fri Mar 09, 2018 1:27 pm    Post subject: Reply with quote

Wow, fantastic amount of info there John! Mirrors the advice we got some years ago, and we try to avoid adding anything to the pool other than chlorine. We replaced the liner last year, refilled, and believed that we needed CYA but local pool shop told us not to bother and I believe last season was probably the best year we've had with no pool problems at all! Moral of the story: stop chucking lots of chemicals into your pool. Smile
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casasantoestevo



Joined: 06 Nov 2006
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Location: O SaviŮao, Galicia

PostPosted: Fri Mar 09, 2018 3:08 pm    Post subject: Reply with quote

Teapot a pool of information. Smile
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Dusty



Joined: 19 Dec 2012
Posts: 294
Location: St Cernin de Labarde, Dordogne

PostPosted: Fri Mar 09, 2018 3:29 pm    Post subject: Reply with quote

Thats fantastic Teapot, thank you for putting in the time and effort into that, its really useful.

Do you have a recommendation for a reasonably priced cyanuric acid monitoring kit? I have survived on strips for the past 5 years but continually worry about the cyanuric acid levels (mainly after reading your posts) but have been put off buying the kit as it seems expensive and as I haven't experienced any problem (to date) haven't been able to justify it.
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KathyG



Joined: 28 Jan 2006
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Location: Le Faou, Brittany

PostPosted: Fri Mar 09, 2018 4:14 pm    Post subject: Reply with quote

We've just collected a season's worth of chlorine, to be told that chlorine regulations are/have changed so there are a lot less producers now and subsequently the price of chlorine has risen by 20%.....luckily we managed to get it at last year's prices but this doesn't bode well for the future! We also received for the first time ever, a long list of health & safety regulations to go with it.
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teapot



Joined: 23 Oct 2013
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Location: Loire valley

PostPosted: Fri Mar 09, 2018 8:03 pm    Post subject: Reply with quote

Lots of questions there so I will answer each one in turn.
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teapot



Joined: 23 Oct 2013
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Location: Loire valley

PostPosted: Fri Mar 09, 2018 8:11 pm    Post subject: Reply with quote

KathyG wrote:
Wow, fantastic amount of info there John! Mirrors the advice we got some years ago, and we try to avoid adding anything to the pool other than chlorine. We replaced the liner last year, refilled, and believed that we needed CYA but local pool shop told us not to bother and I believe last season was probably the best year we've had with no pool problems at all! Moral of the story: stop chucking lots of chemicals into your pool. Smile

Chlorine in an outdoor pool without CYA has a half life of around 35 minutes, so in around 2 hours any chlorine would have been burned off by the sun. I have been running without CYA in my pool for a couple of years whilst I tried out an alternative product that provides a sun screen and doesn't diminish the chlorine's sanitising power, in fact it improves the sanitation. In a season I got through 4-5 20 litre eau de javel containers whilst maintaining a level of 0.2ppm of chlorine. This past year I added the same alternative but also 30ppm of cyanuric acid. My chlorine use last year was just a bit less than 1 x 20 litre container of eau de javel but I maintained the free chlorine at 1.5ppm.

On a fresh refill I wouldn't expect any issues for the first or possibly second but after that with bathers, sun cream etc.
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teapot



Joined: 23 Oct 2013
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Location: Loire valley

PostPosted: Fri Mar 09, 2018 8:16 pm    Post subject: Reply with quote

Dusty wrote:
Thats fantastic Teapot, thank you for putting in the time and effort into that, its really useful.

Do you have a recommendation for a reasonably priced cyanuric acid monitoring kit? I have survived on strips for the past 5 years but continually worry about the cyanuric acid levels (mainly after reading your posts) but have been put off buying the kit as it seems expensive and as I haven't experienced any problem (to date) haven't been able to justify it.


Yes the best value cyanuric acid test kit is from LaMotte at around £19 + postage but everything is going up so I will check that price and get back to you, it is about 50% less than other companies like Palintest. I can supply if required as I looked around for ages for good testers and by linking with LaMotte I can get the best price. Plus the service I get is excellent.
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teapot



Joined: 23 Oct 2013
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PostPosted: Fri Mar 09, 2018 8:26 pm    Post subject: Reply with quote

KathyG wrote:
We've just collected a season's worth of chlorine, to be told that chlorine regulations are/have changed so there are a lot less producers now and subsequently the price of chlorine has risen by 20%.....luckily we managed to get it at last year's prices but this doesn't bode well for the future! We also received for the first time ever, a long list of health & safety regulations to go with it.

Yes the regulations under the EU are all being revamped, The lecture I attended was held by a French girl, a civil servant who thinks she runs the bloody world. I joked that in france I can buy 20 litre containers of eau de javel that is sat right next to 20 litre containers of hydrochloric acid in any Brico shed. Dangerous, yes very very dangerous so I asked her if her department were looking into that accident waiting to happen? No. (room full of people falling about laughing), I don't expect a Noel card from her.

Problem with collecting a season's worth is after 180 days it is likely to be half the strength it was when you bought it. Chlorine in the higher strengths is unstable and begins to break down, more so if it's in sunlight, warm and transported. Always best to try and the freshest possible.
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KathyG



Joined: 28 Jan 2006
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PostPosted: Sat Mar 10, 2018 8:49 am    Post subject: Reply with quote

teapot wrote:

Problem with collecting a season's worth is after 180 days it is likely to be half the strength it was when you bought it. Chlorine in the higher strengths is unstable and begins to break down, more so if it's in sunlight, warm and transported. Always best to try and the freshest possible.


Yes, in hindsight we probably should have just bought 3-4 especially as we'll actually be back here in May and again in July. Normally this time of the year visit is the last till October, it's difficult to get the changeover staff to keep up with actually physically going to buy chlorine. We bought 10 x 20L yesterday and expect to get through all of that, we used 9 x 20L last year. Think we maybe need a bit of help in that department? Shocked

So should we be putting CYA in the pool after all? And your 'additive'? Our pool is 40,000L.
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leon



Joined: 11 Jan 2012
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Location: niort

PostPosted: Sat Mar 10, 2018 9:04 am    Post subject: Reply with quote

Teapot:[i]
"The lecture I attended was held by a French girl, a civil servant "

If the civil servant had been male, would you have called him a "boy"?

Off subject, but worth asking.
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teapot



Joined: 23 Oct 2013
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Location: Loire valley

PostPosted: Sat Mar 10, 2018 9:24 am    Post subject: Reply with quote

KathyG wrote:


So should we be putting CYA in the pool after all? And your 'additive'? Our pool is 40,000L.


Based on your usage, I would give an emphatic yes!
I am not really a fan of cyanuric stabiliser, perhaps because until very recently the chemistry wasn't fully understood, hence my long post. However as I proved to myself last year it works. I used it in conjunction with the previous additive (ACO) which is effective on it's own but the two together was even better. ACO uses the sun's UV to produce an additional sterilisation so aiding the chlorine and not diminishing it.

There are huge outdoor pools in Bristol just using ACO and they report their chlorine use halved. I would agree with that, adding a bit of CYA into my pool further reduced the chlorine use.

The sunnier it is the better the ACO works. CYA isn't sun dependent so plugs that time when the sun isn't so strong.

If you would like to try ACO for a season or just to go CYA let me know.
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KathyG



Joined: 28 Jan 2006
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PostPosted: Sat Mar 10, 2018 9:35 am    Post subject: Reply with quote

Not sure you saw my earlier post Teapot?

"Interesting, interesting! More concerned about the health of our pool and not having problems during the season than saving money on chlorine. But we're just amateurs..... Are you offering to supply ACO/CYA? Not heard of ACO though. We're in Brittany so slightly limited sun compared to you Wink but if Bristol can do it, we should be able to do it too. Smile"
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Last edited by KathyG on Sun Mar 11, 2018 8:46 pm; edited 1 time in total
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