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The pH value in the pool shows how the water quality is. You can read here the answers to the questions as to why the value in the water is increasing and what methods of regulation are necessary.

In a nutshell

  • pH value depends on the water used for the pool
  • can increase with contamination
  • various measures neutralize the value again
  • regular tests show the history of the value

What the pH value says

The pH level in the pool indicates how basic or acidic the water is. Normal tap water has a neutral value of 7. A value between 7.2 and 7.4 is considered optimal for pools. The upper limit is 7.6. Anything above that should be dealt with. However, the same applies to values that are too low.

Measure the pH in the pool with test strips

Measure pH

Two main methods are used to correctly determine the value. On the one hand, there are test sticks that only have to be dipped in water. The pH value can then be read off a color scale. The second option is special tablets. The pool water is poured into a container, then a tablet is added and the water changes colour. This method also includes a color scale from which the value can be read. With this method, the chlorine value can usually be determined at the same time.

Notice: Only the color scales included in the pack should be used, the wrong scale will result in imprecise values.

Fresh water

Although fresh water is neutral, it doesn't stay that way in the pool. Carbonic acid contained in tap water outgasses and the pH value slowly increases. This happens until the carbonic acid has completely escaped. For this reason, after the first filling of the pool, one should measure the pH value regularly until it no longer rises. This is then the starting point for further measures. If you don't want to wait that long, you can start lowering the pH value beforehand, but it can be expected that it will rise again anyway.

well or rain water

If other water is used to fill the pool, a test should be made before use. Rainwater is often more acidic than alkaline. The same applies to many wells. The water can still be well suited for pools, if the pH value does not adjust itself correctly, you have to help after a certain observation period. A good way to get the pH right is to mix tap water with other acidic water.

neutralize the pH value

Chemical agents are often used for neutralization. These are preparations called pH-Plus (pH raiser, pH +) or pH-Minus (pH lowerer, pH -). Different acids are part of pH reducers. Care should be taken when working with these agents, undiluted they are highly corrosive. The warnings on the packaging should be heeded.

However, adding water with a lower pH value, such as rainwater or well water, may be enough to lower the level without chemicals. A partial water change is also possible, but tap water should not be used for this. The pH value would then inevitably rise again.

Other causes

If the pool has been standing for a while and the pH value is set correctly, you only have to test once a week. If you notice that the value is increasing, you should look for other causes.

  • failed or dirty filter
  • large amounts of organic matter in the pool
  • a lot of bathing
  • high temperatures
  • dirty pool
  • poorly adjusted chlorine level

Notice: Heavy rain also changes the pH value, but in the low range.


  • Thoroughly clean the filter and pool
  • Protect pool from pollution
  • Set the chlorine value correctly

frequently asked Questions

Are there alternatives to chlorine?

A very effective alternative is the complete water change. However, this is also associated with a corresponding effort. Otherwise there are various options, such as the use of other chemicals, a UV system or active oxygen.

Is a high pH in the pool harmful?

It is not fundamentally harmful to health as long as it is not too high. But an increasing value indicates that the water quality is deteriorating. At some point the pool water will tip over and at the latest then you will lose the desire to swim in the pool.

How to better protect the pool?

In larger pools, you will not be able to do without chlorine or similar agents entirely, unless a constant exchange of water is possible. Protection is provided by a good filtration system and the pool cover.

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