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Are you struggling with algae in your pool? Or is your pool water cloudy or milky? Perhaps you have already measured the pH value of the pool water and know that it is too high.

In any of these cases, be sure to read on. Because we’re going to present you with step-by-step instructions on how to lower your pool pH.

If you have enough time on your hands, it also won’t hurt to check out our comprehensive post on pool pH. In it, you’ll learn exactly how it affects the quality of your pool water as well as your pool equipment.

For those of you who don’t have the time right now, we have a quick summary:

The pH value (short for Potentia Hydrogenii) tells you what properties a substance has. In our case, this means how alkaline or acidic the pool water is. The scale of the value ranges from 1 to 14, with a value of 7 being considered neutral. Values above 7 are referred to as basic or alkaline water, while water below 7 is acidic.

The optimal pool pH is between 7.0 and 7.4, and anything outside this range can be harmful to either people or pool materials. Alkaline pool water also inhibits the action of the disinfectant (usually chlorine), which can cause major problems (such as bacterial proliferation, algae growth or insect colonization).

Why does the pool pH become too high?

Usually, the pool pH is too high rather than too low. The following two causes can cause pH to be too high.

Carbonic acid off-gassing: when you refill the pool after the winter break during pool start-up, there is carbonic acid in the water. The carbonic acid is chemically bonded to calcium carbonate. It is therefore water-soluble calcium hydrogen carbonate.

Swirling the water causes the carbonic acid to dissolve from the mixture and outgas accordingly. Since carbonic acid is acidic, the pH increases as a result.

Foreign particles: Most foreign particles can cause the pH in the pool to become too high. It doesn’t matter if it is contamination from leaves, hair, dander, sunscreen or pollen in the pool. All foreign bodies make a certain contribution.

In order to constantly counteract an excessively high pH value, the pool should be regularly cleaned of all visible foreign bodies. This can be done particularly well with a landing net, for example. You should remove coarse dirt with the pool landing net at least every few days.

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If the pool is located near large trees or gets dirty quickly for other environmental reasons, even more frequent cleaning may be required.

Effects: What happens when the pool pH is too high?

A pool pH that is too high can be quickly detected. After only a short time, the effects can be seen. Some consequences of too high a pool pH seem merely annoying. Others, however, are a real danger to bathers.

Literally, the water makes you feel the pH level is too high. The following effects can occur:

  • Skin and eye irritation occur.
  • Algae growth is promoted.
  • The effect of the pool flocculant decreases.
  • The chlorine effectiveness decreases. At a pH value of 8.0, the effectiveness is already at only 30%.
  • Rapid calcification occurs, which causes water turbidity and can clog the pool filters.
  • The pool may produce an unpleasant odor.

Step-by-step lowering the pool pH (with pH Minus granules)

Have you noticed that your pool has one or more of the above symptoms?

If so, however, this doesn’t always have to mean that the pH is too high. Some symptoms can also occur when the pool pH is too low.

In this step-by-step guide, you will learn how to effectively lower pool pH. The chemical used is pH Minus, which can lower the pH level in the pool.

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Step 1: Determine the pool pH

A simple method to determine the pH level in the pool, is to use test strips. Test strips are a quick and inexpensive way to examine the pool water more closely.

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Proper use:

  1. Hold the corresponding test strip in the water for about 10 seconds.
  2. Remove the test strip afterwards
  3. Compare the resulting color with the table on the container (without shaking it off first).
  4. Now read the pH value from the point where the colors match.

Note: Besides measuring with test strips, there are other methods you can use to measure the pool pH. Some methods are more accurate. However, this accuracy also comes with a higher price tag.

Step 2: Determine the capacity of the pool.

Many pool owners will know the capacity of their pool. If you don’t know the number or don’t have it handy right now, you’ll have to use math.But don’t worry – it’s really quite simple.

Depending on the shape of your pool, you can use an appropriate formula to calculate the volume:

(units in meters)

  • Rectangular pool = length x width x average depth
  • Round pool = diameter x diameter x average depth x 0.78
  • Oval pool = length x width x average depth x 0.89
  • Eight-shaped pool = length x width x average depth x 0.85

Note: You only need to calculate the average depth if the pool has a slope. Measure the depth at the deepest point and the shallowest point, add the numbers and divide by 2.

If your pool has a different shape, you can divide the pool into several sections and calculate each section separately. Afterwards, simply add all the volumes together.

If in doubt, you can also contact pool experts who can help you with volume determination as well as pool chemical dosage for your particular pool.

The math is really not difficult. We have prepared here in small example for you:

For a rectangular pool with the dimensions

  • length = 6 meters
  • width = 4 meters
  • depth = 2 meters

would result in a volume of 6m x 4m x 2m = 48m³.

Step 3: Determine the quantity of pH Minus Granules

Using pH Minus Granules is a very convenient and quick way to lower the pH level in the pool. You can get the granules in specialized stores and usually even cheaper online.

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Calculating the amount you need is very simple. Just take the measured pH value and determine how many 0.1 steps you need to lower the pH value to 7.2.

Again, we have a small example for you:

Measured pH: 7.6

7,6 – 7,2 = 0,4

Note: We recommend aiming for a pH value of 7.2. This is, in fact, exactly the middle of our recommended range of 7.2 to 7.6.

The difference to our target value is 0.4.

That makes 4 steps of 0.1 each.

Result: We are talking about 4 steps.

Now determine how much pH Minus granules you need to lower 0.1. This step is even easier than the previous one. Take the pool volume and multiply it by 10.

Calculate again:

Pool volume: 48m³

48 x 10 = 480

Result: You need 480g pH Minus granules to lower the pH value by 0.1.

Finally, multiply the calculated amount of required granules by the number of necessary steps determined above. The result is equal to the total amount.

pH Minus granules: 480g (previous calculation)
Steps: 4 (previous calculation)

480g x 4 = 1920g

Result: You need 1920g of granules to reach the desired pH value.

At a glance: (a new example)
Measured pH value: 8.0
Optimal pool pH value: 7.2
Pool capacity: 30m³

Calculation of steps:
8,0 – 7, 2 = 0,8.
0,8 x 10 = 8
8 steps

Calculation of the amount of granules per 0.1:
30 x 10 = 300g

Calculation of the total amount of granules:
300g x 8 = 2400g

You need 2400g of pH Minus granules to reach the desired pH value.

Note: Always follow the manufacturer’s instructions and only then use our formula. The numbers may be different for the granules you use.

Step 4: Add the pH Minus granules correctly to the water

You can achieve the best possible effect by creating circulation in the pool. All you need to do is keep the pool filter on. Alternatively, you can use a landing net to create some movement in the pool. It is also clever to add the pH Minus granules to the pool at various points.

Note: If you distribute the granules well, you will ensure that they dissolve quickly in the water. This has the advantage that you can go swimming directly afterwards without any worries.

Lowering the pool pH with pH Minus liquid

Another way to ensure balanced pool chemistry in your pool is to use pH Minus fluid. Just like pH Minus Granules, the liquid lowers the pH level in the pool.

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pH Minus liquid is sulfuric acid. In terms of application, pH lowering liquid is similar to the granules presented above. The differences are that you only need about half of the pH Minus liquid. Also, it is recommended to dissolve the liquid with water in a bucket beforehand. This makes it easier to distribute the chemical optimally in the pool when pouring it in.

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Note: When pouring it in, make sure that it does not splash. This is because the sulfuric acid has a corrosive effect. Also, do not enter the pool for up to 4 hours after adding the liquid!

Lowering the pool pH with household remedies

In addition to the methods presented so far, there is still the possibility of lowering the pH with household remedies. The basic procedure is similar to the procedure for lowering the pool pH with granules or the pH minus liquid.

If you want to lower the pool pH with household remedies, you can use vinegar. The rule of thumb is: to lower the pH by 0.2, you need about 100 ml of vinegar per 1 m³.

Example calculation:
Measured pH value: 7.4
Optimal pH value: 7.2
Pool capacity: 30m³

Vinegar for a change of 0.2:
100 ml x 30 = 3000 ml

Result: You need about 3 liters of vinegar to reach the optimal pH value.

Note: We do not recommend the use of vinegar for the purpose of lowering the pH. This is because vinegar is an organic acid that serves as food for bacteria. The following bacterial proliferation provides a higher chlorine demand and additionally stresses the filter system.


A pool pH that is too high brings with it many different problems. Promoting algae growth, irritating the skin and eyes, and inhibiting disinfectants spoil the fun of swimming and turn the pool water green in no time.

But you can always remedy the situation with chemical and home remedies. After all, in this article you learned when the pool pH is too high and how to lower it.

It’s best to prevent it from getting that far in the first place by regularly testing the pool water and readjusting if necessary. Even a small amount of effort can prevent most problems from occurring in the first place.

We hope that we have been able to help you with this and wish you a clean pool with an optimal pH value in the future.

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.