Water Balance: Difference between revisions
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Total alkalinity is the measure of the water's ability to "buffer" from wide pH swings. A buffer is a chemical system that resists change when acids or bases are added to the water. In water with no buffer ability, pH can shift dramatically. These rapid fluctuations of pH levels are called pH bounces, and the result is a highly unbalanced water condition. | Total alkalinity is the measure of the water's ability to "buffer" from wide pH swings. A buffer is a chemical system that resists change when acids or bases are added to the water. In water with no buffer ability, pH can shift dramatically. These rapid fluctuations of pH levels are called pH bounces, and the result is a highly unbalanced water condition. | ||
{| class="wikitable" | |||
! | |||
!Low Total Alkalinity | |||
!High Total Alkalinity | |||
|- | |||
!Impact | |||
|<ul><li>Corrosive water</li><li>Pitting of concrete</li><li>Metals dissolving</li><li>Staining of walls</li></ul> | |||
|<ul><li>Scaling water</li><li>Plugged filters</li><li>Reduced circulation</li><li>Cloudy water</li></ul> | |||
|- | |||
!Non-Balance Problems | |||
|pH bounce | |||
|pH drifts upward | |||
|} | |||
=== Testing === | |||
Total alkalinity, like calcium hardness, is tested by titration. At the endpoint the color changes from green to red. Make sure to follow the directions on the inside of the test kit thoroughly. Observe that some samples will turn from green to purple instead of green to red. This color change can also be used as a reliable endpoint. It is caused by the use of a polymeric biguanide (PHMB) in the pool. | |||
=== False Readings === | |||
The most common problem in the total alkalinity test is caused by a high level of chlorine. When excessive chlorine is present in the sample, one of the two reagents used in the total alkalinity indicator will bleach out. When this happens, the endpoint changes from blue to yellow instead of green to red. To avoid this problem, repeat the test with an extra drop of the first reagent, thiosulfate. This should destroy the excess chlorine and solve the problem. | |||
== pH == | == pH == | ||
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== Calcium Hardness == | == Calcium Hardness == | ||
Water that has little calcium or magnesium in it is called soft. Hard water contains high levels of calcium and magnesium salts and consumes soap, making it hard to form suds. In pools, having too much calcium may cause the water to scale. Having little to no calcium can cause the water to become corrosive or "aggressive" and may eat away at concrete, marcite (pool plaster) or grout. | |||
{| class="wikitable" | |||
! | |||
!Low Calcium Hardness | |||
!High Calcium Hardness | |||
|- | |||
!Impact | |||
|<ul><li>Corrosive water</li><li>Etching of marcite (pool plaster)</li><li>Pitting of concrete</li><li>Grout erosion</li><li>Pitting of the pool deck</li></ul> | |||
|<ul><li>Scaling water</li><li>Plugged filters</li><li>Reduced circulation</li><li>Cloudy water</li><li>Heater inefficiency</li></ul> | |||
|} | |||
=== Testing === | |||
Calcium hardness is tested by titration with an endpoint that changes from red to blue. Be sure to follow the directions on the inside of the test kit thoroughly. | |||
=== False Readings === | |||
The most common error in testing calcium hardness is called a fading endpoint. Instead of observing a well-defined color change and a permanent endpoint, some color change occurs, but the sample then reverts back to its original color. This usually happens due to small concentrations of iron or copper in the pool water, causing the the test to turn purple instead of blue. To remedy, add five or six drops of the titrant to the water sample first, then conduct the test as usual. When a complete color change is observed, add up the drops (including the five or six initially added) to obtain a total. The initial five or six drops act as a bonding agent, holding together the interfering metals so the color change is apparent and the test is conclusive. | |||