In Australia, Europe, and the US, you’re not allowed to operate a public pool if you don’t have a “Certified Pool Operator” (CPO) certificate.

The importance of taking care of a swimming pool is knowing what you are doing when handling chemicals, since it is very delicate and once things go wrong it can go wrong very fast.

For example the chlorine and hydrochloric acid mixup in Disneyland Paris 2018,

It was reported that the chemicals were mixed incorrectly, causing a dangerous gas to be released and the pool had to be shut down. Click here to read the last article about the history and the hazards of chlorine.

So why do pools go green?

There are many different reasons why your pool can go green, and usually the culprit are things that we don't even think about.

If you have a roof without a gutter over your pool then chances are dust, pollen and even bird wastes can be washed into your pool during heavy rain. If your pool is lower or the same height as your yard, soil can also either flow into your pool as well as overflow from the gutter during heavy rain. All of these are great sources of food for algae, and they can grow very quickly which turns your pool green, also known as any pool system’s kryptonite. A common solution to this issue is to chlorine shock your pool.

So what makes my pool cloudy/milky?

There are many different reasons for this as well.

Is the pump, filter or sanitizer undersized?
If the pump is too small, you will have to increase the pump’s run time in order for it to circulate enough water, if that doesn't help you might need to look for a bigger pump.
It is also important to have the right sized filter and sanitizing system for your pool, an undersized filter can hinder your flow and pump’s performance, and an undersized sanitizing system can hinder your sanitizing capabilities.
If you have a sand filter keep in mind these are huge water wasters, and aren't good for the environment. Every time you backwash your sand filter the amount of water you backwash is the same amount of water that needs to be added back into the pool. This causes imbalance in the pool because new water also needs to be sanitized, and rebalanced.
Another thing to keep in mind is if you have a saltwater pool or a chlorine pool, the chemicals will also be washed down together with the dirty backwashed water.
Are the pipes large enough?
With pipes that are too small for the size of the pool there is no guarantee that you’ll have a sparkling pool since you will not get enough flow (increasing the size of the pump does not help), the only solution is to rebuild the pool and lay down bigger pipes.
Is your pH constantly at 7.2 - 7.4?
There is no sanitizing system in the market that will work properly if the pH is higher than 7.8 since a high pH will lower the system’s sanitizing capabilities which can cause your water to turn cloudy or even green.
Does it rain a lot? Is the pool leaking? Is there a lot of new water entering the pool?
When new water is added into the pool through the water level control in the surge tank, skimmer, or rain. It can cause an imbalance in your water chemistry, not only will it cloud up your water but your system will also not be able to keep up with sanitizing your water. This means you will be spending more money on water, longer running time and chemicals.
Are you using impure chlorine tablets?
Be careful when buying chlorine tablets, as some chlorine tablets are mixed with talcum powder to cut costs. This will definitely make your water cloudy.
Chlorine should be at 1.5-2.0 ppm