copper to combat cya

[costablanca blue]

i´ve cleaned pools for a few years and found that customers are reluctant to let me dilute their pools in order to control cya (water is expensive here in spain). the result is that it used to be really difficult controlling algae with high levels of cya.

having spent much time shocking with liq chlor, dabbling with bromine and testing numerous algicides, i eventually found that using copper based algicides were the only way of preventing algae when cya levels were too high.

as many posters on here are from the other side of the pond, i wondered if there is the same difficulty in persuading pool owners to dilute their pools? i´ve tried explaining how swcgs make it easy to control cya but customers tend to be put off by the price of a salt system.

 

[dtlight]

You could check and see if there are companies offering reverse osmosis filtering for pools in your area. You would lose about 20% of the water in the pool during the filtering process, but there would be nothing left but pure water when they were finished.


http://www.calsawayphoenixwest.com/


This is one of the companies that provides this service where I live, perhaps they belong to a trade organisation and could direct you to a company near you.

 

[chem geek]

Did you try Polyquat 60 which has the ingredient Poly{oxyethylene(dimethyliminio)Ethylene (dimethyliminio)ethylene dichloride}? How about phosphate removers? What about 50 ppm Borates (boric acid)? I'm just wanting some more data points about effectiveness of these other algae inhibiting solutions.

I presume that you keep the copper level from getting too high and you keep the pH from rising to high to prevent metal staining, correct? And I presume that chlorinating liquid or bleach are not good options for you, perhaps because you only visit customers weekly? You might take a look at this post and this post to see how some pool services manage a weekly service.

They basically maintain a higher FC level and technically if you keep the FC at least 7.5% of the CYA level then that will prevent algae growth regardless of algae nutrient (phosphate, nitrate) level. If you reach a limit for that, then you need to either dilute the water (not a great option for you), use a phosphate remover (unless that didn't work for you), weekly shock with chlorinating liquid (you said you tried that). The other main approach is to have a high enough CYA level (say, 100 ppm) and raise the FC to around 14 ppm (usually using chlorine gas and chlorinating liquid) so that it drops to around 4 ppm by the time you visit a week later. Because most chlorine is bound to CYA, 14 ppm FC with 100 ppm CYA has the same effect as 4.2 ppm FC with 30 ppm CYA or 0.13 ppm FC with no CYA so far less than indoor commercial/public pools that don't have any CYA.

Copper at sufficient levels can prevent algae growth, but it has the risk of staining pool surfaces and turning blond hair greenish.

 

[costablanca blue]

Hello again,

Thanks for your suggestions. I haven´t seen polyquat 60 for sale here - is that an effective remedy to high cya? I have tried phosphate removers and borate - both of which were completely ineffective when cya levels are too high.

Although there is some copper staining of grout (slight discolouration of grout only) I rarely get complaints from customers about this. If they do notice, I explain about the cya problem and the need to drain water. The customer then tells me to carry on as I am! I´m much more likely to get complaints if the pool goes green but with copper I rarely have a green pool.

Yes, using liquid chlorine would be difficult for weekly visits but thanks for pointing out the links on the subject.

I understand your point about raising FC to 14ppm on a weekly visit but again, I would get more complaints with high chlorine levels (sore eyes, itching skin, etc) than I do with copper and lower chlorine levels.

 

[costablanca blue]

thanks for the link, i haven´t heard of reverse osmosis for pools but i´ll look into it further. is the system commonly used in north america? things tend to lag behind the times a little over here.

You could check and see if there are companies offering reverse osmosis filtering for pools in your area. You would lose about 20% of the water in the pool during the filtering process, but there would be nothing left but pure water when they were finished.


http://www.calsawayphoenixwest.com/


This is one of the companies that provides this service where I live, perhaps they belong to a trade organisation and could direct you to a company near you.

 

[chem geek]

I understand your point about raising FC to 14ppm on a weekly visit but again, I would get more complaints with high chlorine levels (sore eyes, itching skin, etc) than I do with copper and lower chlorine levels.

It doesn't work out that way and people often don't notice that the FC is high because the CYA level is so high. Remember that the active chlorine level that would react with skin is only 0.13 ppm FC with no CYA. It's far less than indoor commercial/public pools, not that this is a great standard to use, but the point is that pool services with 1000+ clients use this system successfully. It's not ideal, but it does work.

I can understand borates only helping up to a point since it's a relatively weak algaecide, but I'm a bit surprised the phosphate remover didn't help since that's what my local pool store uses if algae develops in their 2000 serviced pools, but then again they tend to target 4.5 ppm FC with 100 ppm CYA so they don't let the CYA get that high.

As for Polyquat, I can speak from personal experience (during my first year and a half of pool ownership) that even using it every other week, it let me get to 3 ppm FC with 150 ppm CYA before I had problems so I suspect that if I had used it every week as directed that I could have gotten to 3 ppm FC with 200 ppm CYA. So that's about 1/5th the FC/CYA ratio that would be required for chlorine alone to prevent algae growth. And this was with high phosphate levels in the thousands of ppb. Note that it is possible for the Polyquat to not be as effective in high CH pools, especially above 400 ppm.

 

[costablanca blue]

thanks for taking the time to reply chemgeek. my experience is that people aren´t happy with chlorine levels over 10ppm. i usually ask pool users to stay out of the pool for a while if i´ve had to shock a pool.

do you know if the pool company you mention are permitted to use such high levels of chlor?

 

[harleysilo]

Might be time to invest in some commercial Reverse Osmosis equipment and start doing that! Be the PIONEER in Spain!

 

[jblizzle]

Sounds like you are struggling to understand the relationship between CYA and FC. A FC of 10ppm at a CYA of 100ppm would have lower active chlorine present than a pool with a FC of 2ppm and a CYA of 0ppm (as is required for some public pools over here). Personally I would much rather swim in the stabilized pool as it is less harsh. Keep reading threads and Pool School if you do not understand this.

It also sounds like you idea of "shocking a pool" is not what we call the Shocking Your Pool PROCESS.

BTW, RO treatment is actually very rarely over here. It is only available in 2 or 3 cities that we are aware of ( Phoenix and Tucson in AZ and part of southern California).

 

[costablanca blue]

i didn´t think you were permitted to go above 10ppm fc over there (irrespective of the cya level / active chlorine level)? i was surprised that one of the methods described above involved raising the fc to 14ppm every week.

sorry if i´m being dumb. i´ll go to poolschool for further reading. :?

 

[jblizzle]

Every municipality has different rules about CYA and FC levels for public pools ... many have not yet grasped the interrelationship that has been understood since the 1970s.

For private pools (which this forum is generally geared toward), we can do whatever we want.

The former pool company that was "maintaining" my pool have the CYA up to around 300ppm ... I do not recall how high they raised the FC every 2 weeks, but pretty sure it was WELL above 14 ... likely closer to 30+ppm.

 

[keene3b07]

i can tell you that i maintain all of my pools keeping the cya at 100 and i increase the fc by about 12-14 ppm each week and i dont get algae or have complaints about itchy eyes etc. Periodically if there is lots of swimming or something and the fc when i show up is less than 4, i increase the fc by a lot more than 12-14ppm, which is costly but it has to be done or else you will have algae the next week. I think adding borates are going to help with that though. Overall i think its the best way to maintain a route. Whenever a prospective customer has a cya level of way over 100, i charge a start up fee to raise the fc, and then essentially do the same thing i do with all the other pools. The only difference is when you show up the fc is usually 10 plus ppm.