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Ideally, nothing should spoil the fun of big and small water rats in summer.

But a garden pool is a sensitive ecosystem that can react to even minimal deviations with undesirable side effects.

Apart from exclusively cloudy pool water, brown or green discolorations can also occur. In the worst case, the pool may stink. But even if the pool stinks, there are ways to get rid of the problem, so you can enjoy the cool water again.

Causes of musty pool smell

Often, the water that emits the unpleasant odor is also quite visually evident through cloudiness or discoloration that something is wrong. In principle, pool stench is an indication that there are too many organic compounds, such as algae, in the pool water.

Although the general cause is generally known, it is important to find out in each individual case which step or measures will eliminate the undesirable odor. Normally, with adequate pool maintenance, which includes water quality as well as cleaning of the pool floor and walls, the pool should not stink.

However, it is necessary to look at each individual situation to find clues to the specific cause. For example, after wintering where the pool was covered with a tarp for the pool, there could be an increased formation of algae if the pool tarp was not completely opaque.

Get rid of musty pool odor in 7 steps

Dirty debris in your pool’s water can be accompanied by an annoying odor, though the latter doesn’t necessarily occur at the same time as the former. The reasons why the pool stinks are often due to insufficient water hygiene.

You can usually remedy this with appropriate cleaning measures, which are explained in the following sections.

Step 1: Remove leaves and other dirty debris

Not only plant debris in the form of pollen, for example, but also insects and other foreign bodies should be removed from the surface of the water with the help of a pool scraper. This measure will prevent the formation of additional dirt stains on the bottom or walls of the pool.

Step 2: Brush off the bottom and the walls

Start cleaning the pool with the areas that are particularly dirty, as detached sediment can further cloud the pool water. If the infestation of algae or other organisms is severe, this and the next step may need to be performed several times.

Step 3: Use a pool vacuum

With the help of a manual or automatic vacuum, debris on the floor, and in the case of pool robots, the walls, is removed.

However, if the water is greenish, which indicates an infestation of algae, be careful, because a pool vacuum will spread them further in the water instead of cleaning it up.

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Step 4: Clean the skimmer

Normally, the pool skimmer should be cleaned at least once a week, or as in this case, when needed. In addition to removing dirty debris, this continues to include emptying the skimmer basket so that the skimmer can work optimally.

Step 5: Check the water circuit

Make sure that both the skimmer, the pool pump, the appropriate filter media, the individual filter, and the return glands are in perfect condition and performing at the maximum possible level. Correct any deficiencies that have occurred so that the pool water can be properly filtered.

Step 6: Ensure the functioning of the filter

It is a good idea to check the cartridge filter system or sand filter system according to the specifications of the respective manufacturer. In the case of the latter, the cartridge may need to be cleaned or replaced.

The filter medium of a sand filter system, on the other hand, only requires a so-called backwash, as the sand has a service life of five years on average.

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Step 7: Perform a shock chlorination

Also known as “shock chlorination“, this action cleans the pool of any organic debris such as algae, bacteria and other contaminants. It is advisable to perform shock chlorination at least once a week, or at the latest, when there is a disturbing odor or visual changes in the water.

On the one hand, the above steps can help to eliminate the musty pool smell.

On the other hand, if they are carried out regularly, they also have a preventive effect, both against unpleasant odor formation and against greenish, brownish or cloudy changes in the pool water.

In addition, it is essential to measure the pH value and, if necessary, to adjust it to a value between 7.0 and 7.4 with the help of chemical agents.

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The musty pool smell won’t go away – Now what?

If, despite all the measures taken, there is no improvement in the musty smell and the pool continues to stink, the only option is to restore the pool or the water in it to its original state. In a sense, you perform a reboot of hygiene for your pool.

For this purpose, first, the water of the pool should be changed, always assuming that the pool has been cleaned of algae and other contaminants manually, as well as with chemical means for the care of the pool.

Furthermore, before changing the pool water, it is recommended to perform all necessary repairs to the pool along with the pool accessories, this includes, first, the filter system and the skimmer.

When changing the water, use tap water if possible. Under no circumstances should well water be used, as it may contain elevated levels of ammonium, manganese, nitrate, copper or iron oxide.

Although well water is a cost-effective alternative, you run the risk of discoloration, since iron oxide, for example, leads to a green or brown tint of the pool water when chlorine is added.


Nobody likes to refresh himself in musty smelling and possibly cloudy water. If the pool stinks, the odor is basically due to an increased presence of organic foreign matter, such as algae, bacteria or other living organisms.

An initial analysis of when the pool stink occurred potentially allows you to draw conclusions about the specific cause. However, if you cannot attribute the musty pool water to a trigger such as a translucent tarp that may have encouraged increased algae formation, general hygiene measures and water quality should be reviewed.

Therefore, in addition to the manual removal of contamination, the water circuit as well as the chemical composition of the pool water should be checked for defects. If the filter, the skimmer, the chlorine content as well as the pH level are in an optimal condition and the problem persists, the pool water should be completely replaced with tap water.

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.