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There are a lot of people, especially those with their own garden, who take advantage of the occurrence of rain to water their plants, although, of course, this is also possible in an apartment.

Usually, rainwater can be easily collected, and it also does not come with any additional costs, such as sewage fees or a high delivery price.

Many pool owners wonder if they are allowed to fill the pool with well water, and so is the case with filling with rainwater.

Under what conditions, filling the pool with rainwater will turn out to be a good decision and how to use it properly is the subject of the following article.

Filling the pool with rainwater: Here’s how

There will always be times when you need to refill the pool. Whether it’s because you have a simple pop-up pool that needs to be taken down at the end of the pool season, or even if the water in your pool is only going to be used as wastewater.

In this case, if you want to fill the pool with rainwater, there are some important things to keep in mind!

There are indeed some points that speak against the use of rainwater in the pool, first the agricultural use of land in the surrounding area, which in many cases is accompanied by a large use of fertilizers and pesticides, as well as the presence of a chemical factory.

However, this is usually only the case for a few sites, so rainwater can usually be used. In the following text sections, we will discuss in detail how to counteract factors such as heavy pollution or increased exposure to germs.

Collecting and storing rainwater properly

A decisive factor in whether you can use the rainwater for filling the pool is actually the adequate storage of the same. If, for example, a classic rain barrel or rain barrel is used to collect the water, it should not be used in a swimming pool.

Another thing is to use a cistern, which is state of the art, regulated by the DIN 1989 standard, to collect the rainwater, as this method is generally well suited for those purposes.

Depending on the size of the pool to be filled, the cistern must also have sufficient volume. It is also highly advisable to make sure that the cistern in question has a rain overflow.

In summary, the advantage of this approach is not only the presence of the most modern technical tools, but also the fact that a cistern is usually covered.

Although it is naturally assumed that water should remain in motion, with regard to rainwater it makes more sense to leave it in the cistern for a while before filling the pool with it.

The main purpose of this measure is that the dirt, which the rain carries away from the roofs, can already settle to a large extent on the bottom of the cistern.

However, there is no need to worry about germs or bacteria contamination, as the treatment of rainwater counteracts any undesirable development in this respect.

Treating rainwater

There is no general guideline to what extent and to what extent the water collected from the sky must be treated, as this varies from region to region.

In order to channel the rainwater into the pool, a water pump is recommended that has been ideally adapted in its performance to the individual circumstances on site.

Furthermore, you should explicitly make sure that it is a dirty water pump, as another model may either only work to a limited extent or not at all due to dirt particles still present.

As a rule, the pH value of rainwater is in a range below 7.0, which, however, corresponds to the ideal pH value for pool water.

Due to this fact, in most cases it is inevitable to raise the rainwater from the acidic range with the help of a pH lifter.

Especially fast dissolving products in the form of powder as well as granules are recommended here, because they contain so-called bicarbonates, which benefit the water:

Pool Mate 1-2205B Plus Swimming
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Since the rainwater has ideally been allowed to linger in the cistern for a while, the germ load may have increased, and organic foreign matter can also be found naturally in this water.

In order to be able to guarantee a flawless and hygienic bathing environment right from the first jump into the cool water, a so-called shock chlorination should be carried out.

This is normally done with a pool shocker specially designed for this purpose:

HTH Pool Care Shock Advanced,
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Just like using well-water as well as tap water, it makes sense to prevent the infestation of algae at an early stage, as it often entails costly and labor-intensive removal. As a preventive measure, however, the addition of an algaecide is perfectly adequate.


Provided that the rainwater is collected with the help of a modern cistern and given sufficient time before being filled into the above-ground pool, there is nothing wrong with its use in most cases.

The only exception to this is in areas where there is a high level of chemical contamination, such as in the catchment area of a factory or in an area where there is a high level of agriculture.

Since the pH value of the rainwater must be raised, this step can be carried out promptly in conjunction with shock chlorination and the application of an algaecide.

It is also important to remember that if the pool was previously filled with well or tap water, these measures can upset the existing chemical balance. A review and, if necessary, an adjustment of all water properties are therefore also inevitable.

In order to ensure that the cost-effective water alternative has been used in the long term, continuous pool and water maintenance is necessary.

An initial visual test after two to three days provides good indications of the existing water quality. If neither turbidity nor colored discoloration can be detected, the chances of a prompt, carefree jump into the cool water are very good.

Larry has been a true water rat since childhood. Pure pleasure turned into a passion. That's why he is the first point of contact for friends and acquaintances when it comes to pool-related problems. He is an integral part of the PoolHandbook editorial team.