The most common cause of problems with pool water originates from pool water pH being incorrect. Often the pool pH is incorrect because total water alkalinity is too low. Maintain total alkalinity and pH will be easy to manage, if the water pH is right then the Chlorine is effective and your pool water will not turn green with the first rains of summer or during electric storms.

Green pool Water
1 Correct the pH first, if the pH of the pool water is too high (alkaline) then acid such as Hydrochloric acid should be added. If the pool pH is too low (acidic) then Soda Ash in the case of marbelite pools or Bicarbonate of Soda for Fibreglass and Vinyl pools should be added. When adding acid or alkaline always predilute it in a bucket of water.
2 Add an algaecide, there are a number of products on the market, some work in conjunction with chlorine and some do not, so read the label as to whether there should be no chlorine present in the water or not. Superchlorinating is not always the answer and can often be an expensive way of destroying an algae infestation.
3 Backwash the filter frequently as per the instructions of the algaecide, remember that an algaecide is essentially a herbicide and if you backwash onto the lawn or flowerbeds it may damage your garden.
4 Once the water is clear, correct your total alkalinity first and then stabiliser. These additives take a few days to dissolve properly and therefore no backwashing should take place for 5 days after addition. Adjust one thing at a time
5 Through this whole process constantly monitor and adjust pH as per point 1

High chlorine demand
No matter how much chlorine is added to your pool water, there is never a reading of free chlorine
1 Pool Water Test Equipment is old and giving incorrect readings both pH and chlorine. have the water tested at a pool shop or at use a friends water test equipment to check the readings of your pool test equipment.
2 PH is wrong - if the pH is erratic then check total alkalinity.
3 Little or no stabiliser in the water, have the pool water tested for stabiliser before adding.
4 Filter sand is contaminated and/or backwashing is not cleaning the sand properly. Open the filter tank and check if the sand is clean and not lumpy and change the sand if necessary.
5 If using a chlorinator or chlorine generator, check if the right size is being used and that it is functioning correctly.

Pool water is blue but cloudy
1 Correct pH, check the readings of your pool water testing equipment and test for accuracy.
2 Superchlorinate or shock dose your pool by switching the chlorinator to high and running the pump around the clock for a few days and/or adding a few cups of dry chlorine as well, to get the chlorine to above 7PPM. Do not swim until the chlorine level drops below 2.5PPM.

PH constantly needs adjusting
1 Check total alkalinity 2 Top up water is very alkaline or acidic Chlorinator cell needs frequent cleaning 1 pH is too high - adjust as necessary.
2 Calcium levels are very high. During the first few months after changing to salt water chlorination this is quite normal as dry chlorine contains calcium. Should this condition persist then change part or all of the water with new water with a low calcium level.
3 If the marbelite is rough then it probably was not correctly cured at time of application and is soft and dissolving into the water in which case the only solution is draining the pool and resurfacing.