# Forum Home Renovation Pools, Spa & Water Features  Chlorinator pretends to produce chlorine!

## hemp

I have a 1 year old Zodiac LM3 -40 chlorinator which seems to have stopped producing chlorine.  
Apart from negligible chlorine, pool chemistry is otherwise OK according to the computerised tests. 
The pump is producing plenty of water pressure at the outlets, salt levels are fine, the chlorinator inspection glass shows lots of the whitish turbulent activity I associate with chlorine production, electrodes are clean, salt cell is clean. 
I run the chlorinator currently for 8 hours/night on 3 bars, though I also tried 4 bars. No measurable chlorine the next morning. The timer seems fine, as I've heard the pump running during the night and is off at 7am.  
I tried running the chlorinator on the superchlorinate setting for 5 hours yesterday, but still no measurable chlorine using a test kit. 
I'm currently dosing the pool with liquid chlorine to keep nasties at bay, and the test kit (along with a pool shop test) now shows an appropriate chlorine level. However, when the issue first arose, I hadn't checked the pool for several days, and there was plenty of algae stain on the pool floor. This has now been resolved, and the pool water looks clear and the floor also clean. 
The pool is 8 x 4 M, and is covered with a solar bubble cover when not in use. I've tried to contact the Zodiac seller, Cozy Pools, but not yet heard back from them. 
Any ideas?

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## METRIX

Have you checked the cell to see if there is any damage or build up of calcium on it ? 
You can manually clean it if required, should be in the manual how to do this.
These modules have a 12 month warranty and a 4 year pro-rata warranty after that, might be a good idea to contact the place you bought it from, might be a faulty cell.

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## hemp

Electrodes are clean, salt cell is clean.

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## Bros

If you pass a current through salt water you cant help but produce chlorine which is indicated by the bubbles. I'm not an expert but my daughters cell was cleaned a few times and it was OK but when it was last cleaned a part broke off detecting water flow so I had to order one and have it sent to me.  
Over the time it took to get the new cell the residual chlorine dropped to nothing and when we got the new cell it would not come up so i tipped a heap of liquid chlorine in and with that it finally came good but not with the chlorinator alone. 
Reading up on the solar blanket it doesn't stop the sun penetrating the pool and destroying the residual chlorine. 
Have you added Cynauric acid as this helps with the chlorine. 
The worst thing may be the chlorinator is undersized and it has only become obvious with the more sunlight in summer. 
You say you run the chlorinator on three or 4 bars why not flat out as that is how my daughters runs and it reduces the motor run time and cost.

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## Whitey66

Collect some water right where it goes back into the pool from the salt cell and test that.
Have you checked for both chlorine and combined chlorines ?
If you are using tablets (DPD1) and a chemical test kit add a DPD3 tablet to the test to check if it changes colour. DPD3 tablets test for combined chlorine, which is bad.
Have you shocked the pool? You really need to do this if you have had any sign of Algae. If you haven't, any chlorine you are producing could be getting used up fighting Algae even though you can't see it.
As Bros said, have you checked for Cyanuric acid also known as Stabiliser?
If your Cyanuric acid level is too high, it reduces the effectiveness of your chlorine so make sure it's spot on.
When you said the water balance test is OK, have you got 2 or more tests done and compared them?
I have found that some testing can be way out, causing big problems for the pool owner.

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## hemp

Yes, I took a bucketful from the pool outlet to test during the superchlorinate test. I used a liquid OTO not DPD1. Both total chlorine (0.89) and combined chlorine (0.45) are acceptable according to the Monday store test. Yes, after I noticed algae just after Christmas, I used an algaeside, and I shocked with liquid chlorine.  
I've never needed to use a stabilizer over the past 8 years, believing that the pool being covered all days except for a few hours/week was sufficient. And about 30 years ago with an old uncovered above-ground pool, the cyanuric acid level rose too high and I had to ditch half the pool water. Being on tankwater only, I didn't want a repeat of that. However, yesterday I added 2kg stabilizer to help prolong the liquid chlorine's effectiveness. 
I've had two store tests in the past week and daily home tests - all with similar results. 
The chlorinator model produces chlorine on the high side for my 40,000L pool (up to 60,000L in a temperate climate according to the manual). Last summer it worked fine on 2-3 bars production, and on 2 bars all the rest of 2018. 
As to water flow, the chlorinator's flow detector isn't indicating an issue. 
The only other issue I've noticed is that my pH has been difficult to lower this season. It's never super high (often around 7.8), but though I follow the recommendation sheet from the 4 store tests I've had this summer (usually add around 600ml pool acid) it remains a little high on the next test. Similarly, my home tests suggest pH is high. I must have added about 4-5 litres of acid since November.

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## METRIX

If the cell is ok and clean, have you done an overnight chlorine loss test to see if there is any remaining algae in the pool ?. 
Test the levels just after the sun goes down and record the levels then test first thing in the morning before the sun comes up if free chlorine has dropped more then 1ppm overnight, and combined chlorine is above 0.5ppm  you still have an algae problem even though you can't see it. 
You will need to get the level back up to shock level to kill any remaining algae, sounds like this may be the problem and the SWC cannot produce enough chlorine to counteract what's left in there, obviously goes without saying ensure ph etc are all good as well.

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## hemp

Thanks, Metrix, 
I've just added about 8 litres of liquid chlorine for the 40,000 L pool on recirculate for an hour. 
An overnight chlorine loss test? OK I'll try that if I can get some DPD3 locally. I assume the chlorinator should be turned off overnight for this test?

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## Whitey66

> Yes, I took a bucketful from the pool outlet to test during the superchlorinate test.

  The best way to get a sample is to put a piece of garden hose into the return outlet so you only get water from the outlet, not the surrounding pool water.
What is your TA reading ? (total alkalinity) .
Could you post your pool test recordings on here so we can check them out?
Things like, what is the phosphate level? phosphates are food for algae.

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## hemp

Yes, a hose is a better approach. I'll try that method. 
Alk is 129ppm which is about midway between limits of 100-150ppm 
My local doesn't do phosphates; but a December Clark's test noted phosphate, so I used Phosphate Eliminator. 
Below is Dec 11 prior to my problems arising. And then the local test on Jan 28

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## Whitey66

Phosphates are only really a problem if you don't keep your chlorine in check.
Have you had any of the crazy thunder storms like we've had bringing heaps of dust down with the rain?

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## Whitey66

Phosphates are only really a problem if you don't keep your chlorine in check.
Have you had any of the thunder storms like we've had bringing heaps of dust down with the rain?
The storms we had, caused algal blooms in pools within a matter of hours.

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## METRIX

> Thanks, Metrix, 
> I've just added about 8 litres of liquid chlorine for the 40,000 L pool on recirculate for an hour. 
> An overnight chlorine loss test? OK I'll try that if I can get some DPD3 locally. I assume the chlorinator should be turned off overnight for this test?

  Yes everything must be switched off, what you are checking for is if the chlorine level is dropping overnight more then 1ppm then something is eating the chlorine during the night and because there is no sun. 
Reason you do it overnight is the sun is one of the main culprits for using up chlorine (besides humans and any organic matter), overnight it's expected a small amount of chlorine loss will occur but if it's more then 1ppm then something else is depleting it as you won;t lose that much in one night if the pool is healthy. 
No point having the SWC on generating chlorine because it will be adding chlorine and you wont know if the level has dropped so would give you wrong results.

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## hemp

OK, Metrix 
Would it work if I collect a sample after dusk, keep it free from light. Disconnect pump & chlorinator overnight. Then collect another sample at dawn tomorrow, keep it free from light, and have both samples tested by the store in the morning?  
I just realized that that method won't work, as the overnight sample will still have its chlorine attacking any algae that's present.  
Re phosphates, no crazy weather, but the pool is partly surrounded by paddocks, and we've had the occasional phosphate flare-up over the years. As you see from my data, there was some phosphate in Dec.

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## Whitey66

I don't think you have to worry with the test Metrix suggests, if you shock it there will be no algae left anyway.
If your pool has anywhere for algae to hide eg. behind pool lights. You need to pull them out and clean behind them because algae can live there even after a shock because it doesn't become exposed to the high chlorine mix due to the lack of water flow through that area. If the algae is still in behind the light after the shock, it can slowly spread algae back into your pool water once it starts to multiply rapidly. All pool water has algae in it, it's just that you can't see it till it blooms when the conditions are right.
Algae really is amazing stuff, it can even live in diesel fuel tanks :Eek:

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## Whitey66

> OK, Metrix 
> Would it work if I collect a sample after dusk, keep it free from light. Disconnect pump & chlorinator overnight. Then collect another sample at dawn tomorrow, keep it free from light, and have both samples tested by the store in the morning?  
> I just realized that that method won't work, as the overnight sample will still have its chlorine attacking any algae that's present.

   Can't you just test the chlorine level yourself?
If you don't have the required test kit you can buy a 4 in 1 kit for around $30.

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## METRIX

> OK, Metrix 
> Would it work if I collect a sample after dusk, keep it free from light. Disconnect pump & chlorinator overnight. Then collect another sample at dawn tomorrow, keep it free from light, and have both samples tested by the store in the morning?  
> I just realized that that method won't work, as the overnight sample will still have its chlorine attacking any algae that's present.  
> Re phosphates, no crazy weather, but the pool is partly surrounded by paddocks, and we've had the occasional phosphate flare-up over the years. As you see from my data, there was some phosphate in Dec.

  No it won't work, you need to test the water there and then or shortly after, don't you have some test strips you can just do a quick analysis with so you know if you are making any progression, I know you were looking for some DPD3 locally, but strips are cheap and give quick results and get you back on track easily. 
The test results you posted have you corrected any of the levels since this test ?, you really need to get the PH in check first because this is going to make you go in circles. 
You have very high phosphate levels, normally this is not an issue if the water is balanced, but as your levels are all over the place this is going to cause you recurring issues, high PH will cause algae to keep producing, algae will  feed on the phosphates, chlorine kills algae, high PH causes more algae to grow and so it keep going in circles, you can keep adding as much liquid chlorine as you want, but you must fix the PH first. 
Few things to note:
Algae feeds on Phosphates
Chlorine kills Algae 
Your phosphate levels are way off the chart so any algae left in there will be feeding on the phosphates allowing them to keep thriving, once you fix everything then you can work on getting the hardness level down.

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## Whitey66

> Your phosphate levels are way off the chart so any algae left in there will be feeding on the phosphates allowing them to keep thriving, once you fix everything then you can work on getting the hardness level down.

   The high phosphate levels were back in Dec 11 he said, and he used phosphate eliminator. The more recent test done on Jan 28 doesn't include phosphate levels so where it's at now is anyone's guess till he gets it checked again.
The hardness level in his last test was fine so no action is necessary regarding calcium.

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## METRIX

Yep, The levels need to be checked again to see what's changed, what's started to repair or become worse, without know what the balance is now is like finding a needle in a haystack.
This is why I like the strips for quick analysis on the spot, obviously not as accurate as a poolshop analysis but good enough to make the right change based on the results. 
Taking a sample to the poolshop and having it analysed, is great if you are completely lost and don;t know where to start, it's also good to confirm what you are doing is correcting the issue after you have had some major water issue.

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## hemp

OK, today's test at Clark shows phosphate has risen again. It will be treated today. 
Chlorine high as expected given the superchlorinate. The pH is finally at the low end of ideal. 
The pool looks very clear and clean.  
I'll take the cover off to let the free chlorine diminish. Once it's down, I expect I can assess whether the chlorinator is working - at present I can't be sure if the reading taken from the hose-on-outlet-to-bucket test represents the chlorinator output or the high current free chlorine level of the whole pool.

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## r3nov8or

As the latest report says, add salt - can't make chlorine without (enough of) it. And I'd be adding stabiliser when it reaches that low level, despite the report saying it's 'ok' - it won't be ok for long

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## Whitey66

> As the latest report says, add salt - can't make chlorine without (enough of) it. And I'd be adding stabiliser when it reaches that low level, despite the report saying it's 'ok' - it won't be ok for long

  This is why you need to learn to test your own pool water and not listen to pool shops.  The recommended level of salt for the Zodiac LM3-40 is 4000ppm, and it's already 785ppm over that.
The more stabiliser you have, the higher ppm of chlorine you require. Free chlorine ppm should equal about 7.5% of the stabiliser ppm. So running it at the lower end of the "OK" scale is a good thing.

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## r3nov8or

> This is why you need to learn to test your own pool water and not listen to pool shops.  The recommended level of salt for the Zodiac LM3-40 is 4000ppm, and it's already 785ppm over that.
> The more stabiliser you have, the higher ppm of chlorine you require. Free chlorine ppm should equal about 7.5% of the stabiliser ppm. So running it at the lower end of the "OK" scale is a good thing.

  The same manual states 40-100 ppm for stabiliser, so it's very low at 30.

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## Whitey66

> "Rubbish" right back at you. The same manual states 40-100 ppm for stabiliser, so it's very low at 30.

  That's funny, I have a copy of an LM3 manual and it clearly states 30 - 50ppm, the same as the Australian Standard.
Check where your manual came from, my guess is that you googled it and got the US version and not the Australian one. Those yanks are often different to us.
The more stabiliser you have in your pool, the harder the chlorine has to work to fight the baddies. In this case, more is not better.

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## Bros

Be good you pair the "rubbish" has been take out

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## r3nov8or

> That's funny, I have a copy of an LM3 manual and it clearly states 30 - 50ppm, the same as the Australian Standard.
> Check where your manual came from, my guess is that you googled it and got the US version and not the Australian one. Those yanks are often different to us.
> The more stabiliser you have in your pool, the harder the chlorine has to work to fight the baddies. In this case, more is not better.

  Well, that's funny, I googled the Au manual, and it says the AS is 30-50 and that the *Ideal Reading is 50*. https://www.blpumps.com.au/wp-conten...zodiac-lm3.pdf (tell me it's not the latest or something  :Smilie:  ) 
So I will stand by my related statement that stabiliser run at the lower limit (30 here, and well below Ideal Reading per the equipment manufacturer) will soon be below the lower limit, as it was in the first of the OP's test results, and will be a contributor to the lack of chlorine. 
From the Zodiac Au website
"You should also check the cyanuric acid level of the water.  If this has dropped too low it will mean that your chlorine is burning off in the sun.  ..." 
Now, we all know that, but just in case we need a reputable source  :Rolleyes:

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## hemp

> That's funny, I have a copy of an LM3 manual and it clearly states 30 - 50ppm, the same as the Australian Standard.
> Check where your manual came from, my guess is that you googled it and got the US version and not the Australian one. Those yanks are often different to us.
> The more stabiliser you have in your pool, the harder the chlorine has to work to fight the baddies. In this case, more is not better.

  Yes, my Australian manual states 30-50ppm. The Clark recommended salt level is inconsistent with the manual's which ranges between 4000-7000ppm

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## r3nov8or

> Yes, my Australian manual states 30-50ppm. ...

  That's the AS. Are you listening to the manufacturer's Ideal Reading?

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## Whitey66

The only thing you need to know from the chlorinator manufacturer is how many ppm of salt their chlorinator is designed to work at. The only reason they put the ideal reading down as 50ppm is that most people only add stabiliser at the start of the swimming season. In most cases 50ppm at the start will carry them through the swimming season. Cyanuric acid is only lost through splashing, backwashing filters etc. where water is lost from the pool excluding evaporation.  
This is from NSW health website -   If cyanurate concentration exceeds the maximum concentration of 50 mg/L the disinfection rate is too slow and diseases could be more readily transmitted. The optimal concentration of cyanuric acid is 30 mg/L.   FYI - 1 mg/L = 1 ppm

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## Bros

Looks like you need a degree in water chemistry to manage pools, beyond me.

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## r3nov8or

> The only reason they put the ideal reading down as 50ppm is that most people only add stabiliser at the start of the swimming season. In most cases 50ppm at the start will carry them through the swimming season.

  Conducted a survey,  have you?

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## phild01

> Looks like you need a degree in water chemistry to manage pools, beyond me.

  I never progressed beyond fishponds :Erm Smile:

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## Whitey66

> Conducted a survey,  have you?

   Now  Can you explain why they tell you to put in 50ppm when the optimal is 30ppm then?

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## r3nov8or

> Now  Can you explain why they tell you to put in 50ppm when the optimal is 30ppm then?

   Does every salt chlorination system manufacturer state 50 ppm for the reason you mention? (i.e. because people only check once a year) 
I test my water in a couple of ways (don't rely on one method, and the pool shop test is another method again), but test all year round, and mostly I use test strips (simple convenience) which include a test for cyanuric acid, so I see the result very frequently. You didn't survey me, and I think I'm typical of your average pool owner who likes a nicely balanced pool. (My brother, on the another hand...  :Smilie:  )

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## Whitey66

Here is a chart to show that there is very little difference  between 30ppm and 50ppm (maybe 2%).
There is a big difference in the amount of free chlorine needed for the different levels though.
30ppm - 2.25 chlorine
50ppm - 3.75 chlorine
This means a difference of 66.7% more chlorine needed for a 50ppm pool.
I don't know about you but the less chlorine I have to have in my pool to do it's job the better. 
The OPs stabiliser level was low for the first test because he said he hadn't used any for 8 years after a bad experience with a previous above ground pool, not because it magically disappeared. 
Having 50ppm stabiliser is like filling your fuel tank in your car every week even though you may only ever use half a tank that week. Ideally you should only fill it half way because that would give you better fuel economy, but we fill it up a) as insurance that we won't run out and b) our time is valuable. 
Some chlorine comes with added stabiliser, if you set your level to 50ppm then add this chlorine you could easily go over the 50ppm maximum. I suspect that's what happened to hemps above ground pool because stabiliser doesn't fall from the sky (unless it came in with the tap water?).
Pools with cartridge filters lose less stabiliser than pools with sand filters because there is no backwashing, if the OP had a cartridge filter and had minimal splashout and rain, the stabiliser could be ok for the rest of the swimming season. 
What type of filter does your pool have hemp?

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## r3nov8or

So why would Zodiac, a highly respected player in this market, state ideal range for free chlorine as 1-3 and ideal reading for cyanuric acid as 50? It's a little baffling

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## hemp

> Here is a chart to show that there is very little difference  between 30ppm and 50ppm (maybe 2%).
> There is a big difference in the amount of free chlorine needed for the different levels though.
> 30ppm - 2.25 chlorine
> 50ppm - 3.75 chlorine
> This means a difference of 66.7% more chlorine needed for a 50ppm pool.
> I don't know about you but the less chlorine I have to have in my pool to do it's job the better. 
> The OPs stabiliser level was low for the first test because he said he hadn't used any for 8 years after a bad experience with a previous above ground pool, not because it magically disappeared. 
> Having 50ppm stabiliser is like filling your fuel tank in your car every week even though you may only ever use half a tank that week. Ideally you should only fill it half way because that would give you better fuel economy, but we fill it up a) as insurance that we won't run out and b) our time is valuable. 
> Some chlorine comes with added stabiliser, if you set your level to 50ppm then add this chlorine you could easily go over the 50ppm maximum. I suspect that's what happened to hemps above ground pool because stabiliser doesn't fall from the sky (unless it came in with the tap water?).
> ...

   
Yes, for the old pool I did use stabilized chlorine, until we overdosed and had to dump half the precious pool water. The other reason I hadn't bothered with stabilizer since 2010's new pool is because it has a solar cover in summer for almost all time other than the few hours/week when it's in use. My understanding from reading online has been that the cover markedly reduces a pool's chlorine requirement by shielding it from UV, but also by deflecting a lot of organic material, like leaves, dust etc that promote algae. I note that one earlier comment in this thread suggested that I'm mistaken about the UV protection. What does the science say? 
I use a sand filter - Waterco s600 Micron High Rate Granular Filter

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## Whitey66

> So why would Zodiac, a highly respected player in this market, state ideal range for free chlorine as 1-3 and ideal reading for cyanuric acid as 50? It's a little baffling

  Who says they are respected? Have you done a survey? because you didn't survey me  :Smilie: 
The very same company recommended pool owners in the USA to have between 40ppm to 100ppm stabiliser in their pools, so you work it out.

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## Whitey66

> Yes, for the old pool I did use stabilized chlorine, until we overdosed and had to dump half the precious pool water. The other reason I didn't use stabilizer is because the pool has a solar cover in summer for almost all other than a few hours/week when it's in use. My understanding from reading online has been that the cover markedly reduces a pool's chlorine requirement by shielding it from UV. I note that one earlier comment suggested that I'm mistaken. What does the science say? 
> I use a sand filter - Waterco s600 Micron High Rate Granular Filter

  It depends on how long you take the cover off and at what time of day. They say you can lose up to 75% of your chlorine in just 2 hours of exposure to the sun without stabiliser.

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## r3nov8or

> Who says they are respected? Have you done a survey? because you didn't survey me 
> The very same company recommended pool owners in the USA to have between 40ppm to 100ppm stabiliser in their pools, so you work it out.

  Ooh, burn 
But thanks. Imitation is the greatest form of flattery

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## hemp

> It depends on how long you take the cover off and at what time of day. They say you can lose up to 75% of your chlorine in just 2 hours of exposure to the sun without stabiliser.

  Thanks for all the help. I've learned a number of things. 
 One is that phosphates may have been one cause of my pool issues. I've ordered a phosphate test kit and 2.5 kg starver pack - both from ebay. I'll routinely test for phosphate and keep it under control. I noticed a comment that if the pH/FC/CYA relationship is correct then phosphates will struggle to become problematic. Have I got that right? 
I'm now testing every two days for chlorine and pH. Chlorine is still very high, so I've temporarily stopped the chlorinator.  
pH has risen outside the recommended range again, so another 600ml of pool acid went in. Is elevated pH a byproduct of the algae breakdown? Might my addition of the 1kg of stabilizer also have raised the pH? 
Pool now looks crystal clear.

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## Whitey66

> Thanks for all the help. I've learned a number of things. 
>  One is that phosphates may have been one cause of my pool issues. I've ordered a phosphate test kit and 2.5 kg starver pack - both from ebay. I'll routinely test for phosphate and keep it under control. I noticed a comment that if the pH/FC/CYA relationship is correct then phosphates will struggle to become problematic. Have I got that right? 
> I'm now testing every two days for chlorine and pH. Chlorine is still very high, so I've temporarily stopped the chlorinator.  
> pH has risen outside the recommended range again, so another 600ml of pool acid went in. Is elevated pH a byproduct of the algae breakdown? Might my addition of the 1kg of stabilizer also have raised the pH? 
> Pool now looks crystal clear.

  You need to turn off the chlorinator and leave the pool blanket off till the chlorine levels are normal.
You shouldn't have the pool blanket on as the high chlorine level can damage the blanket.
You then need to check the chlorine output of your chlorinator.
Do a full water balance test paying close attention to total alkalinity and phosphates.
Phosphates won't cause algae on their own but just think of them as food for the algae if it gets out of control due to high PH and contaminants in the pool.
If the phosphates aren't there the algae won't thrive as well and will be easier to kill off.
Have you checked the PH of your water you are topping up the pool with?
This could be the reason for needing acid, when I top mine up with tap water I always have to add 300 - 400mls of acid even though my tap water measures at a PH of 7.6 .
Adding stabiliser will lower the PH because it's an acid, not an alkali.
The salt chorinator raises the PH of the water by the chlorine generation process.

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## hemp

Thanks Whitey66, 
I've attached my most recent shop test. The total alkalinity looks OK.  
My water supply is from a 90,000 L concrete tank. I measured the tap water pH at 6.6-6.8. I thought concrete would tend to have an alkaline impact on the water. However, it is 40 years old so maybe it no longer has a significant alkaline influence. I believe rainwater is slightly acidic from its reaction with CO2 in the atmosphere. So, it appears that acidic rainwater wins the pH battle at the tap. So, the main cause of the elevated pool pH is the effects of the chlorinator. 
My phosphate test kit should arrive this week.

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## hemp

So, I let the chlorine level fall to low, and tested the chlorinator output, and it was OK.  
So, I set chlorinator for max output (5 bars out of 5, but not on its superchlorinate setting) for 8 Hrs/night and left the pool alone for a few days.  
When I next looked, the pool floor was algae-ridden (mostly dead) though the water looked clear. How come this occurred again? My chlorinator is designed for a pool twice my volume, but still couldn't maintain an adequate chlorine level. Then I had another Clark's test - see below    
Elevated phosphate again (1.5), and low chlorine. So, I vacuumed, superchlorinated with liquid chlorine, and set the chlorinator to its superchlorinate setting for 24 hours. Then, when chlorine level rose (as instructions indicated) I added the recommended quantity of phosphate starver (600ml). I also added a kilo of stabiliser which had fallen somewhat. I also added a tile and a half (maybe 1000-2000 l) of fresh water to lower the calcium level. The pool level was a little low due to a slight leak in the solar heating plumbing (now fixed). 
Next day, I retested phosphate using my newly arrived phosphate test kit. It read around 2-3 mg/l phosphate. So, I added another 300 ml of starver. I'm unsure what scale Clark's use for their phosphate test. When they read 1.5 is that mg/l too as the results don't readily compare with mine? Because, after the addition, my number elevated further from 1.5 on the Clarks test prior to adding starver to 2 the next day on the home kit after phosphate addition. Surely, it should have reduced? 
I also had my tap water tested for phosphate in case I'm picking up phosphates off my roof and into my tankwater (which feeds my pool). However, no phosphate was detected in the tapwater. 
So, I'm back where I started with either a chlorinator that is under-producing or one that has all its production used up while battling algae which is being constantly fed by phosphates. I'll monitor phosphates and chlorine daily, and restart the chlorinator when the ideal level is reached. 
I've removed the cover until chlorine levels fall to normal

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## Whitey66

A decent test should include "combined chlorine" so i'd give that mob the flick.
Did you read my post #15 above?
When you said you let the chlorine level fall too low, did you have the chlorinator turned down or off?
If you check your PH and chlorine regularly the phosphate shouldn't be an issue, but it's better to be rid of it.
Do you have lots of leaves or other plant matter sitting on your pool cover?

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## hemp

> A decent test should include "combined chlorine" so i'd give that mob the flick. 
> Hi Whitey, 
> If you look at the top right of the Clark's chart you'll see total chlorine is 0.4. I assume that's what you'r referring to?  
> Did you read my post #15 above?

  Yes, I read all the posts. Are you referring to pool lights hiding algae? I haven't checked inside them for years, as neither of them work. Are they really a likely source for the level of issue I'm experiencing?   

> When you said you let the chlorine level fall too low, did you have the chlorinator turned down or off?

  Chlorinator off, but pump still running to schedule - so I could be sure of what level of chlorine the chlorinator started with.    

> If you check your PH and chlorine regularly the phosphate shouldn't be an issue, but it's better to be rid of it.

  I can't see what else could be the culprit, other than phosphate.   

> Do you have lots of leaves or other plant matter sitting on your pool cover?

  A few shrubs within 10 metres, but no trees within 40 metres of the pool - those leaves we get are mostly blown off pretty quickly. 
I should reiterate that we've maintained this pool for the last 8 years with few issues, apart from phosphate from time to time.

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## hemp

OK, I've now got the phosphate down to none showing on test. Chlorine is holding at a high level, so I've cut back to running 5 hours/night, and checking the level daily. Fingers crossed.

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## Whitey66

> OK, I've now got the phosphate down to none showing on test. Chlorine is holding at a high level, so I've cut back to running 5 hours/night, and checking the level daily. Fingers crossed.

  The secret is to check it regularly so you can see any changes and act quickly before it becomes an issue. Why don't you want to remove the lights to check for hidden algae? It's only usually a couple of screws and they should be extra low voltage so it's reasonably safe and doesn't require an electrician.

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## hemp

OK, yes, it's not hard to remove the covers, and I can even unplug the 230v connection at the powerpoint.  
But, am I looking for a dirty algae coating on the pool light walls? Will the ingress of chlorinated water immediately clear out any algae present? Should I scrape the inner walls of the light fixture, and/or squirt some algaecide into the space?

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