The reason why people add chlorine in their pools?

The most simple response is the fact that most people would like to be capable of swimming in stagnant bodies of water without becoming sick, or having the pool transform into an unnatural pond, such as this:

No chlorine + no circulation + no filtration = a natural pool!

Instead, they would like their swimming pool to be safe for swimmers for swimming in, and appear like this:

Chlorine plus circulation and filtration create a pool that can be swum!

Functionally, there are three reasons to add chlorine to pools.

In killing pathogens, such as viruses and bacteria (sanitation)

killing algae since chlorine is ALSO the most effective algaecide for swimming pools. Copper solutions can also be effective but they make the pool black or blue, and hair turns green. Other algaeacides aren't very efficient, except in certain conditions.
Eliminating 'pool goo' since chlorine is the only effective oxidizer of 'poolgoo that is primarily people goo (pee or poop, snot sweat, lotion, and so on.). Commercial pools that are heavily used will become totally cloudy within a single day without chlorine . . . It is a simple result of unoxidized 'people goo'.

Filters are able to remove particles, but the majority of "people goo' is in liquid form or is too tiny for filtration.

Ozone is a more powerful oxidizer, but it isn't always practical. German DIN standards function very well, however they are expensive, complicated and potentially dangerous if they are not managed properly. US Ozone systems are intrinsically secure . . . because they create only a tiny amount of ozone and have no effect.

What are you looking for to build the perfect swimming pool? 

A swimming pool can make a wonderful addition to any backyard, but constructing one is not an easy DIY task. In the majority of cities, it isn't permitted to build your own pool, since the construction process must be overseen by a licensed construction worker to ensure that the pool is in compliance with the code. 

The process of installing is the same, regardless of regardless of whether you're building an acrylic, fiberglass, or concrete swimming pool. Begin by deciding on an appropriate site for your pool, before deciding on the ideal shape and depth. The next step is to hire the building team, who will clear the space and install the electrical and plumbing wiring to learn more about swimming pool and finally pour concrete or install an insulating liner that will withstand water before filling up the pool. 

How much do swimming pools cost?

It is possible build an average gunite in-ground pool for around $40 to $50,000. This is probably the rock bottom price from a budget-friendly pool company.

On the other end of the spectrum I have worked on a pool which was worth more than $4 million ago. This was for one or the founding fathers of Apple but i can't tell the name of the person but it was not a financial issue for this man.

I am sure that there are more expensive pools being built. If you've never been in the business of pool construction you would not know that there are a lot of fanatics regarding their pools. The limit is only the sky. One year later the money is still sitting in a pit, nobody is has ever used it, yet it costs the company money to keep it running! There's no way!