What Causes High pH in Pools

Water pH is a measure of the acidity of water tested and is the most routine pool water test along with chlorine residual that a pool operator will perform at the very least every day of the week.  Pool pH will always fluctuate constantly, especially when you are dealing with so many variables as in a swimming pool. What if the pH moves and you find a higher pH level in the daily test? What causes high pH in Pools?

  • Sudden rise in water temperature
  • Water features that take water out of the pool aerating it
  • Release of Carbon Dioxide(CO2)
  • Swimmers using sunblock or lotions 
  • Liquid bleach, such as Clorox has a pH level of around 11-13
  • New pool surface and walls leaching in H2O
  •  Off-gassing
  • Use of Algaecides

There are way too many explanations on the internet that can be more simply explained especially when it comes to the chemical balance of your swimming pool because most of what happens in your pool is a response to pH moving in either direction upsetting that balance.


What Causes High pH in Pools


If your swimming pool is experiencing high pH conditions and gets excessively high, the water becomes overly soft. Swimmers can develop skin irritation alongside dryness and red eyes. Too high a pH level can also damage piping and pool equipment. The use of chemicals like Algaecides does not directly affect the pH balance in pools, but too many algae will raise the pool pH level by increasing chlorine demand after the initial kill.

Disrupting the balance of the pool H2O chemistry can be an easy thing to do so make sure you have a basic understanding of the H2O test you’ll be running, you have a reliable kit and fresh reagents before Testing Pool Water.

That’s not all pool water with a pH that’s too high can cause scaling, damage to the equipment, and mechanical components, where ever the water comes in contact with filters, pumps, and pipes which in turn hampers the effectiveness of the pool’s circulation system and increases the cost of maintenance.

That spike in the pool pH will deplete disinfection capabilities leading to an increased demand for chlorine. Trying to adjust for less disinfection will increase the costs of chlorine. If you operate a pool high pH levels in your pool will have the same negative results as lower pH levels do on the pool water chemistry. You know the drill so if you’re pH is out of wack then your water chemistry is out of wack and if the chemistry of the pool water is out of wack then you are in for a long summer.


Carbon Dioxide-Pool Chemicals-Sodium Hydroxide Raise Pool pH


There can be several reasons why your swimming pool developed high pH readings such as a

  • Additional chlorine stabilizers and sudden increases in temperature
  • Water features that take water out of the pool aerating it
  • Carbon Dioxide CO2
  • Swimmers using sunblock or lotions 
  • Liquid bleach, such as Clorox has a pH level of around 11-13
  • New pool surface and walls leaching 
  • Result of the chemicals or products used to


If the pH level of pool water is becoming too alkaline and rises above 7.8 then you can expect the water to become cloudy and to see scaling along the pool sides. Metal parts of your pool can also corrode, vinyl linings may wrinkle, and algae can raise the pH further.

When you add chlorine, especially liquid chlorine it is going to affect your pH levels by raising.  An increase in water temperature can also increase your pH levels. Being aware of what is going to affect your pool’s pH levels is helpful when trying to maintain a proper level of 7.4 to 7.6. in your pool water.

Thanks to a scientific equation called Henry’s Law, we know that (Carbon Dioxide) CO2  will off-gas until it reaches equilibrium with the air above the pool. That point of equilibrium is basically a limit or a ceiling. Since pH rises as CO2 leaves the water (off-gassing) this is the pH ceiling of a swimming pool.

Simply put, the more CO2 in the solution in the swimming pool water the more acidic it becomes creating low pH, and the less the base. If the swimming pool becomes alkaline or has more base then it will create a high pH.

Can You Swim in Pools With High pH


Can you swim in a pool with high pH?

Yes, According to the Centers for Disease Control and Prevention, When testing pool water, the pH level considered to be ideal and safe for swimming ranges from 7.2 to 7.8. This range matches that of our body’s pH levels, so the water won’t cause problems in the body as we swim.

The problem is that the chlorine disinfection rate won’t be as potent as it would be with a proper pH reading in the water may not be as effective as it normally would and you may be exposing yourself and others to harmful microorganisms that are escaping chlorine dosage.

Some of the causes of PH being high would be if you have a saltwater pool, it’s constantly making sodium hypochlorite which is already high in PH. Another reason might be a new pool surface. Those pool services can leach alkaline materials for up to two years, so you might find yourself adding muriatic acid all the time

How to Lower Swimming Pool pH


When swimming pools are covered with non-gas permeable covers, such as the common blue bubble solar blankets or solid vinyl automatic safety covers, the exchange of gas from water to air (off-gassing) won’t happen and air to water is blocked.

The pH can remain unchanged for many days, even weeks when pool covers remain on the pool. A long-term solution can be done over a period of time as muriatic acid converts to carbonic acid the pH will drop at a slower rate.

In order to bring down the high pH level of your swimming pool water, you can use a liquid acid like:

  • Muriatic acid (hydrochloric acid) 
  • Dry acids such as sodium bisulfate.
  • Using acidic chlorine like trichlor and getting a lot of rain


How to Lower High pH in Saltwater Pools


In Saltwater pools white chunks of calcium carbonate flake off the salt cell and blow into the pool appearing through the return inlets. Temperature is one of the factors that cause snowflaking. Salt cells have a very high pH inside, as well as heat caused by electrolysis.

The loss of CO2 in the salt cell (caused by Hydrogen gas bubbling off) causes the pH to rise in saltwater pools, and it will raise the pH in the pool, if not for the acidic chlorine gas (Cl2) that neutralizes it.

If it’s a short run of pipe, and the return inlets are aimed up at the surface especially when the return is situated closest to the filtration equipment, there’s a chance that chlorine gas may not have quite enough time to dissolve all the way. You could potentially lose some, which could cause the pH to rise faster. Also, check these reasons for a higher pH:

  • Check the stabilizer level (cyanuric acid) in your pool water. Some will rise the pH is normal in a salt pool.
  • Check your run times on your salt system. The salt system should be able to maintain your chlorine level on 8 – 10 hours of run time in the hottest months of the summer. If you have to run your system 12 – 16 hours per day or more to maintain a chlorine level, then go back and check the stabilizer level.
  • Check Chlorine Output Percentage- If you are trying to get 5 ppm levels, then you are probably running the system too hard to get there and that will result in high pH levels from the long run times.

In order to bring down the pH level of your Saltwater pool, you can use a product just like a regular Freshwater pool:

  • Muriatic acid (hydrochloric acid) 
  • Dry acids such as sodium bisulfate.

If you are going to add Muriatic Acid to drop pH and Alkalinity read my article on getting your pool water soft and silky.

What causes high pH can be a result of the chemicals or products like the sanitizer used to stabilize the swimming pool.


Swimming Pools With High Chlorine and High pH


When the pH level in your pool goes above 7.8 pH, your pool water is considered to have high pH. This means that your pool water is now too soft, and there can be consequences. A high pH level can be caused by several negative factors, the main culprits being additional chlorine stabilizers and sudden increases in temperature.

In addition, high pH runs a risk with your chlorine, as your chlorine will no longer disinfect completely. There are also physical consequences of high pH for swimmers. Red irritable eyes, dry skin, and premature wear and tear of goggles and bathing suits are often indicative of a high pH level.

If the pH gets higher than 7.8, the water is becoming too alkaline. When water is too alkaline, it reduces the effectiveness of chlorine the pool chemical that kills pathogens. Water with a pH that’s too high also can cause skin rashes, cloudy water, and scaling on pool equipment.

Over time, scaling inside pipes can build up in your pool, restricting water flow and putting a strain on your pool circulation system that can lead to costly repairs.


What Causes Low pH in Pools?

The main culprits are:

  • Chlorine tablets with stabilizer (CYA)-2.9 pH
  • Rain 5–5.5 pH
  • Children’s urine 6.0 pH
  • Shampoos 4.5-6.0.pH
  • Beer 4.00–5.00.& Ales 3.00–6.00 pH
  • Coffee 4.85-5.1 pH & Soda 2.5 to 3.5 pH
  • Leaves that fall are below 6 pH
  • Skin products & Cleansers: pH 4.5–7. ………………………………………..Read more


JimGalloway Author/Editor


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