Maintaining Proper Alkalinity and PH in Pool Water.  

by Pool Builders on 03-06-2014 in Articles

Maintaining proper alkalinity and pH levels in your pool water is vital, as these are factors that can cause burning of your eyes when swimming. It is also important to understand that alkalinity and pH are not the same thing.

Alkalinity is the capacity of water to neutralize acids. This capacity is caused by the water's content of carbonate, bicarbonate, hydroxide and occasionally borate, silicate and phosphate. On the other hand, pH is an expression of the intensity of the basic or acid condition of a liquid. Furthermore, alkalinity and pH are different because water does not have to be strongly basic (high pH) to have a high alkalinity.

However, confusion often comes from the fact that some of the chemicals commonly used in swimming pools will simultaneously raise and lower both readings - causing people to have problems maintaining the proper levels of both alkalinity and pH. Fortunately, I can offer you an easy (and inexpensive) remedy. To raise pH and alkalinity, I recommend using plain old ordinary baking soda (which also happens to be significantly cheaper then the pH or alkalinity increaser the pool store will try to sell you). To lower either of these, use muriatic acid. The key to adjusting these levels is to add half of the amount required for the change you want - then wait 24 hours and retest before adjusting further. Remember this is not brain surgery - there is nothing super critical here, so don't be in a hurry for instantaneous results. By waiting 24 hours and retesting, you greatly reduce the risk of overdoing it and then going though the whole yo-yo, up and down thing. Also remember that it is far better to err on the side of higher pH than lower. A 6.8 pH will burn your eyes more than 7.8 - with 7.2 to 7.4 being ideal.

When it comes to chlorine levels in pools, some people may be confused by the different types of chlorine present - and they are also unsure of which type of chlorine to test for in their pool. Swimming pool water generally contains three types of chlorine commonly known as Free Chlorine, Combined Chlorine and Total Chlorine. Free Chlorine is the type that we commonly test for to determine the proper chlorine levels in pool water.
To understand the difference between the three types of chlorine, consider this simple formula: FC + CC = TC. Free Chlorine is the chlorine that is still available to sanitize your water. Combined Chlorine is the chlorine that has already been "used up€ sanitizing your water. And Total Chlorine is the sum of the two.

Think of it this way: when a chlorine compound is added to swimming pool or spa water, it reacts with water to form the compounds known as hypochlorous acid and hypochlorite ion. Together, these compounds are known as "free available chlorine€ or "free chlorine.€ The primary reason for adding chlorine to swimming pool water is to disinfect or kill possibly harmful microorganisms. But once the Free Chlorine has joined with ammonia and nitrogen compounds to form Combined Chlorine, its ability to disinfect is hindered. It actually takes 25 parts of Combined Chlorine to do the work of one part of Free Chlorine. If the Total Chlorine in your pool is higher than the Free Chlorine reading, then the difference between the two represents the level of Combined Chlorine in the water. If the readings are the same, then no Combined Chlorine is present. The Total Chlorine level cannot be less than the Free Chlorine level.

Once you know how much Combined Chlorine is in the water, you have to add about 10 times that amount of Free Chlorine to get rid of it. This overdosing - or super-chlorination - is also referred to as "breakpoint chlorination.€

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