How To Treat A Pool Filled With Well Water For The First Time

4 important steps to treat pool water for the first time

So you have filled your pool for the first time. It seems beautiful and clear, right? Well, we recommend you take a good picture of it as long as you can, because from now on if you do not intervene punctually in proper cleaning and water treatment, the water quality will soon begin to drop.

In this article, we are going to answer the most frequently asked questions by new pool operators. These questions include: how do you treat swimming pool water? what chemicals do you need to put in a new pool? how do I treat water hardness? how do I get rid of slimes and green algae, when can I swim in my new pool? And for those who know the basics of water chlorination, how much shock do I need to open my pool?

How To Treat A Pool Filled With Well Water

If you are a beginner with your above ground pool and you do not know where to start and what procedures to follow for proper maintenance, what you absolutely need to know is that the water in a pool changes some certain chemical conditions continuously.

Without mincing words, let’s roll out the step-by-step procedures on how to treat pool water for the first time.

Ready to take note?

Guide to treating pool water for the first time

What you’ll need

  • Chlorine tablet or powder
  • Scale and stain preventer
  • pH regulators
  • Shock chlorine granules
  • Water stabilizer
  • Clarifiers
  • Algaecide
  • Test kits for chemical balance

Step by step instructions

  1. Adjust the pH level
  2. Make chlorine disinfection
  3. Control the hardness and alkalinity
  4. Control green algae with an algaecide

Let’s explain further!

The basics of how to treat pool water

Just filled the pool with water, now what?! After filling an above ground pool for the first time, there are quite a number of steps required to prepare it ready for private or public use.

Before going into detail and start talking about the use of chemicals, you would do well to inform yourself about the properties of water with a chemical test kit.

Knowing its characteristics will help you with the dosage of chlorine and pH. And remember to analyze the water at different depths, because the suspension characteristics may vary.

It is useful to remember that you have to carry out these checks every 3-4 days at the beginning of the season (in the months of March, April, and May), and every 2 days in the months of June, July and until the end of August.

How to adjust the pH level of pool water

After checking the quality and properties of the pool water, you have to proceed with the pH analysis, another fundamental parameter for the correct chemical balance of the pool water.

Water balance is an essential parameter because it ensures effective disinfection of the pool. PH values that are too high or too low cause skin and eye irritation, corrosion of metal equipment and the ineffectiveness of chlorine.

How to adjust the pH level of pool water

Be very careful: the ideal pH value of a swimming pool’s water, above ground or underground, must be between 7.2 and 7.6 to ensure effective disinfection and clear water. If you’re lucky enough to already have stable pH values (rare but possible), then you do not have to do anything.

However, most of the pools have excess alkalinity and require intervention with a pH reducer (the need to raise the pH is much rarer).

Following the specific instructions of the pH regulators, you must add it to the water until the pH has stabilized at optimal levels (you should keep the level monitored for the next 2 – 3 days to understand it).

In getting this value, you have two options:

  • If the pH is too low, you can raise it with acidity/basicity correctors, called “pH +”, and always keep in mind that high temperatures and chlorination tend to increase its value naturally.
  • If the pH is too high, you can lower it with acidity/basicity correctors, called “pH-“. Do not forget to always check the pH value before proceeding with any chemical product.

How to make chlorine disinfection of pool water

Once the pH is normal, you can move on to the most important step in water treatment: disinfection or sanitization. Here’s how to chlorinate a pool for the first time.

To decontaminate the pool water, there are various products on the market: bromine, active oxygen, and others. But surely the most effective is the chlorine.

In fact, the most widely used product to perform this function is, without any doubt, chlorine. In part, this is because it comes in very comfortable forms for use (solid tablets, powder, liquid) and largely because it is cheap and available almost anywhere.

Its value is often expressed in mg or ppm and is present in various forms. The correct free chlorine value of the pool water should always oscillate between 0.6 and 1.5 ppm.

How do you get this value? Just act, as needed, with:

  • Chlorine tablets/trichloro: With the gradual release, you can use a tablet with 90% of active chlorine. You have to dissolve it in 100 cubic meters of water.
  • Chlorine powder/dichloro: It is preferable to use one gram of dichloro per day for each cubic meter of water you need treating.

Do you need to shock a new pool

The first thing to do is the so-called shock chlorination or super location. It is simply disinfection that uses chlorine concentrations much higher than normal (about twice, as usual, 10-15g/ m3.) This treatment is the “initial blow” that brings the chemistry of your pool on the right tracks.

During the shock chlorination, it is also necessary to keep the filtration system active longer than usual (in this way, the treatment spreads better).

Learn how to shock a pool with the short video tutorial below:

Advice on shock chlorination

Never throw chlorine directly into the pool if the pool has a liner or resinous or painted surfaces. Even when pouring it into the skimmer, you have to take care of, the granules of the trichloro do not melt quickly and can damage the internal parts.

Dissolve the chlorine in a bucket before throwing it into the water. In this way, you can avoid many of the possible damages mentioned above.

Shock chlorination is useful not only when opening the pool but, in general, when the pool water is very dirty or contaminated.


  • For all the chemicals that you will use in your pool, you will have to scrupulously follow the instructions on the labels.
  • Make sure that no one uses the pool for at least 2 or 3 days until the free chlorine value reaches the ideal value of 1 ppm.

How to control the hardness and alkalinity

There are two other parameters to take into account for a correct treatment of the pool water – hardness and alkalinity. In fact, a further step in the direction of the perfect pool is to control water hardness and alkalinity.

The water hardness is due to the natural presence of calcium and magnesium in it. Too high water hardness can affect some internal components of the pool such as gaskets, nozzles and other elements that can be easily attacked by limescale.

Keeping it under control will allow you to avoid problems with the maintenance of filters and pumps, as well as the pH itself. It can also create encrustations on the pool lining. A good alkalinity level is between 80 and 125 ppm.

You can express total hardness in French degrees (1 ° F = 10 mg / l CaCO3) or German degrees (1 ° D = 10.0 mg / l CaO). The correct hardness values would be between 15 and 50° F which correspond to 8 and 28 German degrees.

Temporary hardness is often linked to the presence of hydrogen carbonates. Following boiling, this presence disappears due to the formation of a solid precipitate of calcium and magnesium carbonates and ceases to contribute to the total hardness, hence, its temporariness.

Permanent hardness is the one that persists after boiling water, mainly due to the presence of chlorides, sulfates and calcium and magnesium nitrates.

To correct the hardness of the water, you can use special products such as sequestrants to reduce limescale and metals in water.

Alkalinity, on the other hand, is an important parameter as much as the pH. Alkalinity has a close bond with the pH and when varying one, it usually also varies the other. You can determine alkalinity by various chemical compounds present in water: carbon dioxide, carbonates, bicarbonates, and hydrates.

Read more: How to lower alkalinity in the pool without affecting pH

How to control green algae with an algaecide

After doing all the analysis of the water described above, all that remains is to overcome the last challenge: the green algae.

In contrast to chlorine and pH, the presence or absence of algae is not measured but is perceptible to touch and sight. The water of a swimming pool with greenish shades is certainly a symptom of little healthiness.

The algae make the walls and the bottom of the pools slippery and therefore dangerous. Do not underestimate the appearance, as the algae color the water with various shades of green depending on their developmental stages. You could find yourself bathing in a swamp led by fungi and bacteria.

It is, therefore, preferable to prevent algae using a simple algaecide as an adjuvant to curb their birth and their proliferation. Generally, good water circulation, proper chlorination, and precise pH control should be sufficient to avoid their reproduction.

Many people believe that an algaecide is only a repair tool which they can use only when they see algae, but this is a big mistake. The preventive algaecide is useful also and above all as prevention to avoid the onset of visible algae. If you are having problems with algae processing, it is advisable to add the algaecide every week. In case of cloudy water, even after whole filtration cycles, you can use a clarifier.

Types of algaecide on the market

There are different types of algaecides on the market:

Those based on copper can block algae growth and are particularly effective against mustard or green elements. This type is non-foaming, which is a great advantage, but, if not used correctly, can cause stains on the surface of the water. You cannot use them in pools that exploit biguanide salt disinfection.

Types of algaecide on the market

The quat or polyquat algaecides are usually made of quaternary ammonium instead of copper and have a different operation. These products have fewer chances of staining the pool. If you have already had problems with metals, it is better to use this type. The quat type can, however, cause foam, while the more expensive polyquat avoids this inconvenience.

For dosing of the algaecide follow the instructions of the product purchased.

Final checks

Here are all the steps that will allow you to always have a clean and safe pool.

Use the two weeks following these operations to check that everything is working correctly. It is necessary to test the main values, such as chlorine and pH, very frequently with the appropriate drop or pad tests.

After this period, you can be more confident that the pool water treatment has had its effect and that you can proceed with standard water maintenance.

We hope this article “How To Treat A Pool Filled With Well Water For The First Time” will really assist you in your pool operation.

Let us know about the end results if you eventually practice these procedures.

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