“I keep my chlorine at 4.0 or 5.0 (when we are swimming) and the pH between 7.2 and 7.6. The water is always clear so I don’t have to worry about anything else.” Absolutely, totally, completely, 100% wrong!
Assuming that the pool owner/cleaner is using a simple OTO test-kit (Total Chlorine and pH) then the pool will sooner or later suffer a total disaster and, at any given time, there is no guarantee that the water is safe for bathing.
The OTO test for chlorine and pH are fine for testing on a weekly basis but there are two other vital tests that should be carried out regularly.
Cyanuric Acid and Total Alkalinity
The CYA test should be carried out once a year and the TA every 3 months. Both should be checked whenever there seems to be a problem
If stuff like this is inclined to keep you awake at night or bite your nails to the quick then just take a sample (of pool water, I mean) to your pool supplier, carry out any instructions to the letter and forget the whole thing – otherwise read on!
I mention the cyanuric acid only because it has a minor effect on the TA and is not the subject of this article. However, it should be noted that problems start with CYA in excess of 150 ppm and above 350 ppm the sanitizing effect of Chlorine is severely compromised.
Total Alkalinity in swimming pools refers to the relative balance between the alkaline and acidic elements in the water.
High TA (200 or more) results in excessive scale formation on tiles, pipes and metal surfaces and (generally) a high pH. Sanitization with Chlorine is severely compromised and usually results in murky, smelly water.
Low TA (40 or less) results in corrosive water, blue/green or brown staining (from copper or iron deposits), damage to metal parts (pumps, steel steps, pool heaters etc.) and (generally) a low pH. Chlorine becomes aggressively irritating causing sore eyes, prickling skin – or worse.
Properly Balanced Water (80 to 120) is neither corrosive nor scale forming and the water is considered buffered (has a stable pH). The water is generally silky smooth, clear and sparkling.
Generally Costa Blanca Water (Tap or Tanker) is almost ideal to start except that the TA is a little high, around 220.
The use of TriChlor (Granules or Tablets) tends to lower the TA. Lots of pool suppliers and even professional pool cleaners use Soda Ash (Sodium Carbonate) to counter the acidity of TriChlor and raise the pH. In my view this is a mistake because it raises the pH without raising the TA. Very often, if Baking Soda (Sodium Bicarbonate) is used instead, there is never any need to adjust the TA for months.
If the TA is totally ignored for years it eventually falls below 40, the pH begins to fluctuate wildly. Often pH minus (Muratic Acid) is added unnecessarily and the TA falls even further. Finally, somewhere below TA 30 the pH falls off the bottom of the scale and some real damage start to occur – tiles are damaged, the grouting goes green and severe corrosion occurs to metal parts.
The whole process is inevitable. It may take just months and could even take years; it really only depends on how much fresh (High TA) water is introduced but it has to happen in the end if TA checks are neglected.
How do I check and adjust the TA? Simply purchase a DPD Test Kit for Free and Total Chlorine, pH, Acid Demand and Total Alkalinity. I would recommend the Taylor K-1004 because it provides charts to help with TA adjustment.
You would also need a Cyanuric Acid test-kit and there are fairly simple to use.
Trade-off between TA and pH. Water is a very complicated substance and there are lots of factors affecting TA and pH. We have said that the ideal is 80 to 120 but this is a fairly broad range. Between these values and sometimes above 120 is the TA that will work best for your pool and pH stability around 7.5 should be the deciding factor.
Raising and Lowering the TA: It should be remembered that, if the water has been neglected for a long time and the balance is out by 20 points or more, then the process has to be carried out over several weeks. Best to allow 4 – 5 days and further tests between additions of chemicals.
The reason is that corrosion or scaling would have already occurred and certain elements have to be dissolved out or back into the water.
To raise the TA: Only baking soda (Sodium Bicarbonate) will do this. It will raise the pH as well but this should fall back after a few days.
To raise the pH without Raising the TA: Use Soda Ash (Sodium Carbonate).
To lower the TA: Sulfumant (Muratic Acid) should be added in a single column into the deepest part of the pool with the filter switched off for at least 30 minutes.
To lower the pH without lowering the TA: The acid should be distributed slowly over a large area. The best way is to pour it slowly into the return jets stream.
The very worst scenario: If the TA is below 40, the pH below 7.0 and has been like this for several weeks it might be best to drain. Before you decide to do this –
- Check the grouting for hardness. If it can be scraped out with a fingernail then it will eventually all fall out and you will have to drain anyway.
- Look at the colour of the grouting. If there is bad blue/green or brown staining can you live with it? It just won’t go away even when you put the TA right.
- Check the Cyanuric Acid. If this is over 150 you will soon start to have difficulties. If it is over 300 then proper sanitization is impossible.
Sorry if anyone finds this worrying but I did warn at the beginning. After chlorine and pH, TA is probably the most important factor and should never be neglected.
POOL WIZARD: Adjusting the Total Alkalinity ASK ALAN: Total Alkalinity and pH Homefinder 
ARTICLE: Swimming Pool Water Balance | Total Alkalinity & pH 
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