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Another Algae problem - help!


jerrytlr
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Hi sorry to post yet another 'green pool' problem - I promise I have read some of the previous threads on the subject, but am still not sure what to do.

Here is the basic info:

- recently installed 10 x 5 in ground pool

- about 70m3

- was fine for several weeks with lots of users, was happy maintaining water with just multifonction tablets

- suddenly went green over about 2 days. I mean really green - cannot see the bottom of the pool type green.

- big dose of Chlor Shoc

- no difference at all the next day.

- measured water again - alkalinity seemed low, added bicarb which brought it back in range

- another big dose of Chlor Shoc, no difference at all the next day.

- measured the water, pH high, so added loads of pH- until it is now in the right range

- another big dose of Chlor Shoc, no difference at all the next day. pH still in range. Chlorine level reading is still near zero.

Filter running 24hrs a day during all of this.

Used 3 different water testers and all seem to be giving a more or less consistent result, apart from the alkalinity which seems hard to measure .

It seems I am adding Chorine to a pool with a good pH level, and it is doing nothing. It is a brand new tub of Shoc by the way...

Any thoughts on what is going on here, and what I should do next?

From the previous threads, I wonder if I should add plain Javel from the supermarket instead of Shoc??

Water is very soft in my area.

Any help gratefully received!!

Cheers,

Jerry
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Hi - agriculture is pretty much 100% cattle, very little fertiliser or weed control chemical use. The pool is about 10m from the nearest trees.

It is in a location exposed to a lot of sunlight, and we are still in the process of building the terracing so when it was being used quite heavily a few weeks ago there was probably higher than normal dirt ingress into the pool. It is not possible to see how much dirt is sitting on the bottom though!

It is also not covered at all at the moment, as without the terracing being finished, we cannot install the cover (this should all be done within the next couple of weeks).

Hope this extra info is useful!

Can I post a picture on here? May help confirm that it is indeed algae (I am pretty sure it is, but best not make any assumptions...)

Cheers

Jerry
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[quote user="jerrytlr"] I wonder if I should add plain Javel from the supermarket instead of Shoc?? [/quote]

Jerry is it a liner pool?

With all the multi function and choc containing cyanuric acid this leads to a build up of that in your pool, whilst you do need some too much is unhelpful.

Yes I would switch to javel from a brico 20litres for around 19€

With a pool (swamp) you will get through it quickly.  You probably need to add about 10litres to start with and then regular additions to maintain the high chlorine level 10+ ppm so best buy 2-3 20 litres bidons of javel.  Your pH will climb but don't worry as it will fall again as the chlorine gets used up. Better if you start from the lower end of the pH scale. Don't worry about other levels ALC etc as they will all move around whilst you are doing this.

With luck the pool will change back just as quickly and will go blue and cloudy in a few hours, keep filtering for 24 hours or more until it clears then backwash the filter and rinse.

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No Jerry the advice is the same, just don't delay treating this.

If you have a liner pool you can afford to ignore the usual ALK levels pretty much, I run my pool at around 60ppm which prevents the pH drift as our fill water is already 240ppm.

A good tester for the money is the Scuba+ from Lovibond, (not the standard Scuba).

To stop it happening you need to maintain the chlorine level, lots of people being in your pool would have caused it to run low and a floating tablet dispenser probably couldn't keep up, consider a chemical dosing unit and a pH dosing unit.

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Whomever initially balanced your pool water chemistry might have added too much Cyanuric Acid (CYA) aka stabilizer or conditioner to start with.  That would make any chlorine you subsequently add less effective and allow algae to grow.  If you have a test kit that can check the CYA level, I suggest you do that.  If it's high, then a partial drain/refill will be needed eventually so doing it sooner would let you shock more effectively.

By the way, when one refers to "Chlor Shoc", what is that?  I certainly hope it isn't Dichlor which would only exacerbate the problem by increasing the CYA level.

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Nobody has ever added any stabiliser... unless it has been added due to the chlor shoc or the multifonction tablets I have been using.

I have just ordered a tester that is capable of measuring the CYA to see if that is the problem. Unfortunately it won't arrive for a few days.

In the meantime, I added 10 litres of Javel from the brico this morning, and will add some more this afternoon - I'll see if that makes any difference.....

Thanks for all your help

Cheers,

Jerry
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Quick update - the javel seems to be working! Chlorine level read nice and high a short while after adding it and the green colour is starting to fade.

After a few hours chlorine had fallen way back again so I added another 10 litres. Hopefully a couple more cycles like this will clear it...

Cheers

Jerry

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Now been through 4 cycles of 10 litres of Javel, the pool looks a lot less green but still very cloudy (can't see the bottom even at shallow end). Do I just need to keep the filter running until it clears? It has been running 24hrs/day for a few days now....

Or do I just need to keep the chlorine level up high until the cloudyness goes away?

TIA for your advice

Cheers,

Jerry
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Jerry you haven't mentioned what type of filter you have. If its a sand type then what you have done is fine. However if its a paper cartridge type it will be very clogged up by now and will need a new cartridge.
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Hi - I bought the tester you recommended of course :-)

Zeolite - that's it. I am backwashing quite regularly.

Looking at it today I think the algae is winning again - chlorine had dropped once more and I didn't have time to do anything with it yesterday, now it looks a bit greener than a couple of days ago....

So back to the brico to get more Javel on Monday.

In the meantime I have put some multifonction tablets in to try and stop the chlorine dropping any further - bad idea, or good idea...?

Really need that tester to arrive so I can check the other parameters. The test strips I am using at the moment are showing low chlorine (as of this pm) but all other parameters about spot on....

Cheers

Jerry

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Jerry

I would only put Javel in. The problem with any multifonction tablet is that it does raise CYA which, whilst stabilising Chlorine loss, does mean the higher the CYA the more Chlorine you need. I always keep 2-3 20 litre bidons of Javel just in case.

This year I turned up and the pool was green. I put 20 litres in and within 2 hours the pool was blue, but cloudy. Javel really is the way to Choc.

Search this forum and you will find tables showing for a given level of CYA how much is required for a Choc - some of the ppm numbers are really very high.

Rgds
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I'm still waiting for the tester to arrive.... so still not sure where my CYA level is...

However I have gone back to adding Javel - 24hrs in and the chlorine level is nice and high again but the pool is still very green.

I'm beginning to think that abandoning it until next spring is the way to go too!

Cheers

Jerry

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Have you tried adding copper sulphate? Copper is a potent algeacide / bactericide. Some galet multifonction include it, albeit as a small percentage of the weight.

I use about 1g for every 1000l of pool water as a opening / closing treatment. This is not a concentration that could in any way be harmful to bathers. The copper sulphate should be disolved in a bucket of warm water before addition to the pool.

The advantage of using a copper based treatment is that is does not add to the CyA load in the pool.

Do not, under any circumstances be tempted to add Bordeaux mixture: that is not the same thing at all. If you can't find copper sulphate locally, you can get it from here:

Mondroguiste

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