Pool care for beginners

[CarlD]

Hi and welcome!
What Richard (Chem_Geek) is trying to tell you is that your emphasis is potentially dangerous. Clear water is great, but there can still be dangerous contaminants in it.
Therefore the relationship between the Free Chlorine level and the CYA level is crucial to safety. When your CYA is 70, you need to be maintaining your FC level between 5 and 10ppm, not 1.5-3ppm. It's just not safe. Our "Best Guess Table" is really the way to go to stay safe on the relationship between FC and CYA. IF you monitor your FC levels and adjust them, you can safely maintain water with a CYA as high as 100ppm.

And, personally, I think that a higher CYA when you close for the winter isn't a bad thing as it will probably drop, but in the spring you may have a higher level than zero.

Tri-chlor tabs can be great when your CYA is low and your pH is high. They are acidic and add stabilizer. But if your pH is on the low side, and your CYA is ideal or even high, they are a bad idea.

As for your calcium levels: If you have a vinyl-lined pool, you don't really need to worry about calcium until it passes 400ppm or even 500ppm, and only then if your Total Alkalinity is in the 180-200ppm range. Beyond that you make get scaling and cloudy water. The first answer is to cloudy water (from calcium, not algae), of course, get your T/A down to the 100 range and see if it clears up. There's no reason to drain water when calcium hardness is at 300ppm. If you have a concrete, tile, plaster, etc type pool, calcium hardness should be maintained between 200 and 400 ppm, and Total Alkalinity kept under 125ppm. But, again, a calcium hardness of 300ppm is fine.

Bleach/liquid chlorine. It WILL mess up clothes if you aren't careful. But it doesn't have to. 15% concentration is higher than we get in the USA--usually the pool stuff is rated at 12.5%, but if it's fresh and new, I've tested it at 14% frequently. At higher concentrations, you need to keep it cool and dark as it WILL degrade more rapidly than lower concentrations. Ordinary laundry bleach should be available in Spain and is easy to handle. It ONLY adds FC, and doesn't affect CYA or pH. That is why we recommend it.

A final note: If you use a salt water chlorine generator (I do) your relationship between FC and CYA needs to be at least 5% (much lower than the Best Guess table) because the constant and steady infusion of chlorine into the water. So if your CYA is 70ppm, you need to keep at least 3.5ppm of FC--lower than the recommended 5-10ppm. Plus, most systems recommend a CYA of 60-80ppm.

[Anonymous European in Spain]

Dear all,

I really appreciate your comments and recommendations. This is now perfectly understood. Although there is an excellent guidance on this matter on the website, I did not realize that a CYA of just 70 ppm (that I had taken as a kind of máximum level) requires a so high FC level (between 5 and 10 ppm) !!.

Regards,

C

[chem geek]

Don't forget that a critically important part of what is taught here is understanding and taking control of your pool. That usually requires a proper test kit and we recommend the Taylor K-2006 (see this sticky post for more info). Unfortunately, you may not be able to get that in Spain. The next best kit you can probably get in Europe is the Palintest SP 315C though ideally also the Palintest FAS-DPD kit as well.

You can certainly use Trichlor or Cal-Hypo if you know what you are doing and understand the consequences. Between the two, if your CH isn't high already then Cal-Hypo may be a better choice. The downside is that you have to add chlorine to the pool every day or two since the typical outdoor pool exposed to sunlight uses around 2 ppm FC per day. Of course, this will depend on the weather in your area and also on pool temperature (some chlorine is broken down from sunlight while some is from reacting with organics in the water and with pool covers). The purpose of these sites is to give you the knowledge to be able to control your pool and not let it control you. The key is to maintain an appropriate FC level for your CYA level since that will properly disinfect the pool and prevent algae growth.

[Anonymous European in Spain]

Very useful. Thanks again !!
C