Why isn't my pool's pH rising even though I'm using a pH Increaser?
If you've been adding pH increaser to your pool for days and the pH isn't rising, or it rises but drops again within a few hours, this article explains exactly why this happens and how to fix it. The cause is almost always the same: the water's alkalinity is too low. Here, we explain the difference between both parameters, why one depends on the other, and the correct order of correction.
The most common problem nobody explains well
Every summer, thousands of pool owners experience the same situation: they measure the pH, see that it's low, add pH increaser, wait a few hours, measure again, and the pH has barely risen. Or worse: it rose a bit in the morning but by late afternoon it was already low again. The usual response is to add more product, spend more money, and end up frustrated without understanding what's wrong. And almost no one explains to them that the problem isn't with the pH increaser, but with something that needs to be corrected first.
That something is alkalinity. In this article, we explain everything clearly and with concrete examples so you can solve the problem once and for all.
The difference between pH and alkalinity: the two parameters that are always confused
Before understanding why pH doesn't rise, it's crucial to be clear about what each parameter measures. They are two distinct things, although they are related.
pH: the value everyone looks at
pH measures the acidity or basicity of water on a scale of 0 to 14. The optimal range for a pool is between 7.2 and 7.4. Above 7.6, chlorine loses effectiveness. Below 7.0, the water becomes corrosive and can irritate swimmers' skin and eyes.
Alkalinity: the parameter few look at but controls everything
Total alkalinity measures the water's capacity to resist pH changes. It acts as a buffer: when it's in its optimal range (between 80 and 120 ppm), the pH remains stable against any disturbance. When it's low, the pH fluctuates uncontrollably, rising and falling several times a day even if nothing is added.
Imagine trying to maintain the temperature of a room with all the windows open. You can turn on the heating as much as you want, but as soon as outside air enters, the temperature changes. This is how pH works when alkalinity is low: no matter how much pH increaser you add, any disturbance (rain, swimmers, chlorine) immediately destabilizes it.
Now imagine the same room with good thermal insulation. The temperature remains stable effortlessly. Similarly, with alkalinity in its optimal range, the pH resists external changes and only needs minimal adjustments to stay in the correct range for days.
Why pH increaser doesn't work when alkalinity is low
This is the key to everything. When the water's alkalinity is below 80 ppm, the water has such low buffering capacity that it neutralizes the pH increaser almost as soon as you add it. In other words, the product does work, but the effect lasts a very short time because the water doesn't have enough stability to maintain that new pH level.
A concrete example to understand it well
Imagine you have a pool with a pH of 6.8 and alkalinity of 40 ppm (very low). You add pH increaser in the morning. The pH rises to 7.2. In the afternoon, swimmers arrive with sunscreen, or a little rain falls. These disturbances, which under normal conditions would barely affect the pH, now cause it to drop back to 6.9 because the water has no capacity to absorb that impact. The next morning you measure it and it's low again. You add more increaser. The cycle repeats indefinitely.
However, if you had raised the alkalinity to 100 ppm before correcting the pH, those same swimmers and that same rain would have moved the pH by barely a few tenths, which the system itself would have absorbed without a problem. A single pH correction would have lasted days instead of hours.
Continuing to add pH increaser when alkalinity is low is the most common and most expensive mistake. Not only do you spend more product than necessary, but continuous pH adjustments can cause alkalinity to drop even further, creating a vicious cycle that is difficult to break without understanding the root cause.
The solution is not more pH increaser. The solution is to raise alkalinity first and then correct the pH. That order is non-negotiable.
How to diagnose if your problem is alkalinity
Before buying more product, the first thing to do is make a correct diagnosis. For this, you need a complete test kit that measures the three key parameters: pH, total alkalinity, and free chlorine. Basic test strips only measure pH and chlorine, so they are not sufficient in this case.
Low pH + low alkalinity (less than 80 ppm): this is the most frequent case. The cause of unstable pH is low alkalinity. You must correct alkalinity first and then pH. Do not add more pH increaser until alkalinity is in range.
Low pH + correct alkalinity (80-120 ppm): alkalinity is not the problem. In this case, you can directly correct the pH with the increaser. Also check if too much chlorine has been added recently, as liquid chlorine lowers the pH.
pH rises but drops in a few hours: alkalinity is almost certainly low. The pH does not stay stable because the water has no buffering capacity. Measure alkalinity and correct it before touching the pH again.
Apparently correct pH but cloudy or greenish water: there may be pH fluctuations throughout the day that you are not measuring at the right time. Measure in the morning before 9 am and compare with the late afternoon reading. If there is a difference of more than 0.3, alkalinity is low.
The correct order to treat your pool water
Now that you have a clear diagnosis, the next step is to apply the correction in the correct order. This order is not optional: if you do it in reverse, the result will be ineffective and you will waste twice as much product.
Step 1: Correct alkalinity
- Measure alkalinity with a complete kit. Write down the exact value and calculate how much you need to raise it to reach the optimal range of 80-120 ppm.
- Use our pH and alkalinity calculator to find out the exact amount of alkalinity increaser needed based on your pool's volume.
- With the pump running, dissolve the alkalinity increaser in a bucket of pool water before pouring it in. Distribute it evenly around the perimeter.
- Leave the recirculation active for 4-6 hours. Do not turn off the pump sooner.
- Wait at least 24 hours before measuring again. Alkalinity takes time to fully stabilize. If you measure too soon, the reading may not be representative.
- If alkalinity is still low, repeat with an additional dose. Make gradual corrections: never add everything at once if a large increase is needed.
When adding alkalinity increaser, the pH usually rises slightly on its own. In many cases, after stabilizing alkalinity, the pH is already in the correct range without needing any additional adjustment.
Therefore, waiting 24 hours before measuring pH is key. If you measure earlier and see that the pH is a bit high, you might be tempted to lower it with a corrector, creating an unnecessary adjustment that complicates everything. Wait, measure, and then decide.
Step 2: Correct pH only if necessary
- Once alkalinity is stabilized at 80-120 ppm and 24 hours have passed, measure the pH.
- If the pH is between 7.2 and 7.4, there is nothing to correct. The alkalinity increaser has already done the job.
- If the pH is below 7.2, now use the pH increaser. With the correct alkalinity, the effect will be long-lasting and you will need much less product.
- Add the pH increaser with the pump running, distributing it around the perimeter. Wait 4-6 hours and measure again before adding more.
Step 3: Maintain your measurement routine
- Measure pH and alkalinity at least twice a week in summer. A single weekly measurement may not detect temporary drops after rain or intensive use.
- Always measure at the same time, preferably in the morning before swimming. Values vary throughout the day, and comparing readings taken at different times can lead to incorrect conclusions.
- After heavy rains, always measure within the next 24 hours. Rain is acidic and can significantly lower alkalinity in a short time.
Other reasons why pH doesn't rise
Low alkalinity is the most frequent cause, but not the only one. If you have corrected alkalinity and the pH still isn't rising or staying stable, also consider these situations:
Excess liquid chlorine or trichlor tablets
Liquid chlorine (sodium hypochlorite) has a very low pH, around 11-13 in concentrated form, but when diluted in water, it acts in an acidic way on the balance. Trichlor tablets have an even lower pH, approximately 2.8. If you add large amounts of chlorine frequently, you are continuously introducing acidity that the pH increaser has to constantly compensate for.
The solution in this case is twofold: correct alkalinity to stabilize the system and, if possible, reduce reliance on liquid chlorine or trichlor tablets through better water balance.
Frequent or intense rain
Rainwater has a natural acidic pH, usually between 5.5 and 6.5. Furthermore, its alkalinity is practically nil. Every rain dilutes both the pH and alkalinity of the pool water. If your area has rainy summers, you will need more frequent corrections than in dry areas.
Fill water with very low pH or alkalinity
Tap water varies greatly depending on the geographical area. In some areas, tap water has a slightly acidic pH and low alkalinity, which means that every time you refill the pool level, you are introducing water that unbalances the parameters. Analyze your tap water at the beginning of the season to know your starting point.
Insufficient dosage of pH increaser
Sometimes the problem is simpler: the amount added is insufficient for the volume of water in the pool. Many people estimate their pool's volume inaccurately, leading to incorrect doses. Calculate the exact volume by multiplying length × width × average depth and use the calculator to obtain the precise dose.
| Symptom | Probable cause | Solution |
|---|---|---|
| pH does not rise even with increaser | Low alkalinity (<80 ppm) | Correct alkalinity first, then pH |
| pH rises but drops in a few hours | Low alkalinity, no buffering effect | Raise alkalinity to 80-120 ppm |
| pH fluctuates a lot throughout the day | Unstable or very low alkalinity | Stabilize alkalinity, then correct pH |
| Low pH after every rain | Acid rain + low alkalinity | Measure after every rain and correct alkalinity |
| pH continuously drops with a lot of chlorine | Very acidic trichlor or liquid chlorine | Correct alkalinity + review chlorine dosage |
| pH increaser has no visible effect | Insufficient dose for actual volume | Calculate exact volume and use dosage calculator |
Why low alkalinity is so common in summer
If you have this problem every summer, it's not a coincidence. Summer concentrates all the factors that most consume water alkalinity:
- Increased pool usage: More swimmers mean more acidic organic waste (sweat, sunscreens) that continuously consumes alkalinity.
- Higher chlorine dosage: Heat accelerates chlorine degradation, requiring more frequent additions. Each chlorine addition consumes alkalinity.
- Intense evaporation: Water replenished to compensate for evaporation can have very different alkalinity depending on its source.
- Summer storms: Summer rains, though short, are more intense and can significantly lower alkalinity in a few hours.
Therefore, in summer, it's advisable to measure alkalinity at least once a week and always have alkalinity increaser available for quick corrections before imbalance sets in.
Frequently asked questions about pH not rising in the pool
Below, we answer the most common questions from pool owners who have pH problems:
Why isn't my pool's pH rising even if I add increaser?
The most frequent cause is that the water's alkalinity is below 80 ppm. With low alkalinity, the water has no capacity to maintain any stable pH level. The increaser works, but the effect lasts a very short time because any disturbance (rain, swimmers, chlorine) returns it to the starting point. The solution is to first correct the alkalinity with an alkalinity increaser and, only then, adjust the pH.
What happens if I correct the pH without correcting alkalinity?
The pH will rise temporarily but will drop again in a few hours or days. Additionally, you will waste more product than necessary because you will need to repeat the correction constantly. In the long run, continuous pH adjustments can cause alkalinity to drop even further, worsening the problem. The correct order is always: alkalinity first, pH second.
How long does it take for the pH to stabilize after correcting alkalinity?
After correcting alkalinity, it is advisable to wait at least 24 hours before measuring pH and deciding if it needs correction. In many cases, by stabilizing alkalinity, the pH already falls within the correct range on its own, without needing any additional adjustment. Measuring too soon can lead to unnecessary corrections.
How do I know how much alkalinity increaser I need?
It depends on the volume of your pool and how low the alkalinity is. As a rough guide, to raise 10 ppm in a 50 m³ pool, approximately 500 g of alkalinity increaser is needed. To calculate the exact dose for your pool, use our pH and alkalinity calculator, which gives you the result based on your water volume and the current level of each parameter.
How often should I measure alkalinity in summer?
At least once a week during swimming season, and always after heavy rains or periods of very intensive use. Alkalinity can drop quickly in summer due to heat, use, and storms. Detecting low alkalinity in time prevents pH from becoming unstable and problems such as algae from appearing.
Can I add alkalinity increaser and pH increaser at the same time?
No, they should never be added at the same time or in the same area of the pool. Also, the correct order is always alkalinity first. Add the alkalinity increaser, wait 24 hours for it to stabilize, and only then measure the pH to decide if you need to correct it. Adding both at the same time creates reactions that are difficult to control and can cause neither to work properly.
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First increase alkalinity · Then correct pH · 100% natural products · Spanish manufacturing · Shipping throughout Spain
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