Chlorine Turning Water Green

[fogeshan]

Hi!

I've googled this and it seems that the chlorine (calcium hypochlorite) is oxidizing the copper in the water, turning it green. The only suggestions I've come across is to use metal remover to remove the copper, but I've added copper sulphate to keep the algae under control (works amazingly well), so I don't want to take it out surely?

pH and total alkalinity are within normal ranges. It usually goes back to blue after a day or two but it's pretty annoying.

What else can I do to try prevent this?

Some background:
I switched from using boat loads of chlorine (both stabilised and non stabilised) and non metal algaecide (didethyl dimethyl, ammonium chloride) to a "hassle free" product consisting of a once a month "booster" (copper sulphate and zinc sulphate (I think the zinc acts as a clarifier?)), and 4 packs of calcium hypochlorite - one a week.
This was working considerably better than the previous solution and costing much less too, but then it started going green after adding the chlorine, a few months in.

I've always avoided metal based pool products because you often read that they can stain your pool, but so far no staining.

The product is designed for a 50000l pool, and ours is around 70000l, so I'm doubtful that I've put in too much copper sulphate, although it's possible.

 

[kimkats]

This was working considerably better than the previous solution and costing much less too, but then it started going green after adding the chlorine, a few months in.

This says it all ^^^^^^^^^^^^^ it has caught up to you. Is the water clear but green? Or is it cloudy and green? My guess is clear green. It is from the metals

DO you have a good test kit?

We can help you get your pool back in shape. We will need to ask some more questions after you answer the above.

Kim

 

[fogeshan]

Clear green!

Mmm, I can test pH, total alkalinity, acid demand, and chlorine (i think free chlorine)

 

[JVTrain]

If you have excess copper in your pool, it's going to go green (dependent on pH and FC levels) and will stain blonde hair green over time. There is no getting around it. You will also experience staining of pool surfaces. Any copper level over 0.2 ppm has a good chance of causing green water, staining, etc.

I would strongly discourage continued use of copper based algaecides. IF you had problems with chlorine usage prior to using these products, it's likely that you either had active algae growth due to under sanitation, overly stabilized water. Proper sanitation can be maintained effectively and economically using TFP methods, starting with ABCs of Pool Water Chemistry. The problem now is that once you have metals in the water, it may be difficult to remove.

 

[tim5055]

The product is designed for a 50000l pool, and ours is around 70000l, so I'm doubtful that I've put in too much copper sulphate, although it's possible.

Your water has turned green, so yes - you have used too much. The problem is that many things we put into the pool stay there almost forever. Water evaporates and we add more water, but the chemicals don't evaporate. Unless you have pumped water out all the copper you have ever used is there. It's cumulative.

Now is the time to make a decision, keep following your "copper method" or follow our methods. You really can't do both.... We don't have a magic bullet other than the best pool care chemical there is, chlorine.

The sad thing is, algae can actually be your friend. Copper will kill the algae but it does little or can be too slow to kill pathogens that cause human - human transmission of illness. In a "chlorine" pool, the algae tells us that the pool is unsafe. Kind of like a canary in a coal mine.

You joined back in 2012 with some pump/pipe siiues, but how much Pool School have you read to understand our methods of pool care? I recommend you start with these:
ABCs of Water Chemistry
Recommended Pool Chemicals
How to Chlorinate Your Pool

 

[fogeshan]

Maybe that was a naive thing for me to say I think I put too much trust in pool product manufacturers.

I've read lots of advice online, on this site and others, but I'll have another read through those articles!

The thing is, I'm still getting algae growth - not a lot, just a thin film around the sides of the pool as well as small clumps in the shaded corners like on the stairs. The water is still blue and clear though (if I don't add chlorine). So I'm just surprised that I still get algae growth despite having a lot of copper in the water.

I'm going to stop adding copper sulphate and see how it goes.

I've also read that keeping a lower pH (7.0 - 7.2) reduces the likelihood of the pool turning green from chlorine. Is this correct?

 

[woodyp]

Yet another testament as to why we DON'T recommend the use of copper containing additives to your pool. Maintaining a proper level of FC for your CYA level is all that is required. Keeping your algae "under control" is no where near the same as eliminating it.

 

[JoyfulNoise]

I've also read that keeping a lower pH (7.0 - 7.2) reduces the likelihood of the pool turning green from chlorine. Is this correct?

The chemistry is not that simple. Whether or not copper starts to precipitate is a function of the pH of the solution AS WELL AS the copper concentration. If the copper levels are high enough, then even being at a pH of 7.0 can lead to scaling.

If you don't what your copper levels are, you should have your water tested for copper. Some pool stores will test for metals but the results can be sketchy as is the case with all forms of pool store testing...