Raising Swimming Pool pH

How to raise your swimming pool pH level.

Did you test your pool water and discover your pool pH is too low?  Maintaining proper pool pH levels can be a constant challenge, but every pool owner will encounter a low pH level in their pool eventually, and there are several ways to correct the pH back to the ideal range.

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If you tested your swimming pool pH and discovered you the pH is low, then you need to raise the pH level.  Your water is acidic and can corrode metal surfaces, stripping vinyl pools of their stretching ability and reducing their life span, and dissolving concrete and masonry surfaces.

Importance for your pool

Why raise the pool water pH?

As I mentioned above, if your pool pH is low, you are risking pool surface and equipment damage.  Here are typical problems pools with low pH can experience:
  • Metal surfaces such as railings, ladders, light fixtures, screws, pool cover components, pool heat exchanger and pipes, and any metal surfaces in your pump and filter are at risk for corrosion.  Concrete, plaster gunite or shotcrete, and fiberglass pools can all suffer deterioration in their own way, such as etching, pitting, and delaminating.  Vinyl-lined pools can become brittle and eventually crack and tear.  Additionally, any stone, decorative tiling, coping, and masonry surfaces can also dissolve and deteriorate in acidic low pH pool water.
  • Where do you think all that metal corrosion and dissolved cement and masonry go?  In your pool water of course.  However, the water can only hold so much contamination.  Once the water reaches its saturation point, any extra metals and dissolved minerals go out of solution, and begin reforming on pool walls as discolorations and stains.
  • Low pH also can reduce your ability to control total alkalinity, as low pH reduces the effectiveness of chemicals used to balance alkalinity.
  • You will get big complaints from swimmers, as acidic water will sting eyes, nasal passages, and remove natural oils on the skin, leaving skin dry, itchy and cracking.

I discuss in more detail problems you can encounter with improperly balanced pool water pH, in my article: Maintaining Swimming Pool pH.

Why is my pH low?

There are plenty of things that can lower your pool water pH:

  • Your local water source might have a low pH.  If you continually find yourself fighting low pH, then this might be the cause.  Your local pool service provider would be a great source to get details on the most common problems with your local water.
  • You may have added too much pH reducer in an attempt to lower the swimming pool pH.
  • “Trichlor” chlorine tablets have a low pH, about 2.8 – 3.0.  Bromine, another sanitizing chemical, has a pH of 4.0.  With continued use, both can reduce your pool pH.
  • Shocking the pool will lower the pH, whether you use chlorine-based shock (calcium hypochlorite), or the non-chlorine kind (potassium peroxymonosulfate).
  • Rain picks up impurities in the air, raising the rainwater acidity and lowers the pH.  Outdoor pools, even ones with pool covers, tend to get some rainwater in them.
  • Groundwater or flooding can also introduce local water into the pool.  If it has a low pH, then this can be a source of low pH.
  • Do you have many large pool gatherings with many swimmers? These high bather loads introduce contaminates naturally through persperation, saliva, bodily oils, and on occasion urine and fecal matter.  These contaminates can lower the pH.
  • Dust, grass clippings, leaves, and insects always manage to end up in even the best maintained pools.  This is more organic matter that can lower the pH.

On adding pH increasing chemicals to your pool

Chemicals used to raise the pH often have names like “pH Increaser“, “pH Raise,” “pH Plus,” or “pH Up”.  These are all names for sodium carbonate, or more commonly called soda ash.  Be careful with pool chemical names: Sodium bicarbonate is baking soda, and is used to increase your pool water total alkalinity, although the pH will rise somewhat as well.

I have about a 25,000 gallon pool, and I typically by at least one 50lb bag of soda ash early in the season, then dump about half of that into a 25 pound bucket for regular use.  You can buy small 5 pound plastic canisters, but the price per pound is much higher and you might end up using quite a few every season.

How to Raise your Swimming Pool pH

First test your pool pH level.  Once you know your current pH, you can determine what you need to do to increase that value.

Raising your pool pH with Sodium Carbonate (soda ash)

soda ash, or sodium-carbonate, used as a swimming pool-pH increaser

Raise your pool pH with soda ash, also called sodium carbonate.

  1. Read the instructions on the label, as different manufacturers might contain different percentages of sodium carbonate, although a container of soda ash should simply be 100% sodium carbonate.
  2. Determine how much you need to add, based on your test results.  I recommend adding only 3/4 of what is recommended and retest later until you are comfortable with the effect of adding chemicals to your pool.  The reason is you want to avoid adding too much and end up having to lower the pH.
  3. The instructions might say to dilute the soda ash first.  Follow the product instructions for dilution if this is the case.
  4. Since this usually comes in a powder, try to avoid doing this in the wind.  If applying in the wind is unavoidable, apply the powder downwind from yourself, as you want to avoid getting it on your clothes and skin.
  5. Get down as close to the water as you can, as the wind will easily blow the powder into the air instead of your pool.
  6. Try to add the powder into your pool at the water return jet sight(s). This is where the water comes into the pool.  Avoid adding the powder where at the water inlet sights, such as the skimmer area.  You want to spread the dry acid around in the pool as much as possible, but not into areas that would be pulled directly into the pool pump and filter.
  7. The soda ash will dissolve quickly, so there should be little to no need to spread the powder around in the water with a pole brush.
  8. Wait at least six hours before retesting, but try to wait no longer than 24 hours.

Notes on adding soda ash.

You should only add about 4 pounds of soda ash every 6 hours.  You run the risk of raising total alkalinity if you add too much at one time.

For above ground pools, dump the soda ash over the pool wall.  As above ground pools are often more shallow than a typical diving pool, you may have to spread the powder in the pool to encourage the powder to dissolve.  This holds true for below ground sport pools.

If the manufacture recommends you first dilute the soda ash, then definitely follow their instruction. The reason is their product may react so fast in your water, that alkalinity will be increased with unpredictable affects on your pH.  So, instead of one level out of balance, you now have two.

You should test both pH and alkalinity again within 24 hours after attempting to raise the pH.

Raising your pool pH by adding new water.

filling swimming pool with water

Filling your swimming pool with water might raise the pH slightly.

Water from your local water source is often slightly higher in alkalinity than your pool water should be.  So, adding more water will bring your pH up slightly.  If you are perhaps at 7.4 pH and you knew you needed to backwash the pool filter, you would backwash, replace the lost water, then retest pH.  The water added might be enough to bring the pH up a little.

Tips on Raising your Swimming Pool pH

If pH is really high, test strips and even test kits cannot test below a pH of 6.8.  If this is the case, you will need to add a significant amount of pH increaser to bring that pH value back up to testable levels.  Once you can test pH, then you can fine tune how much more you need to reduce the pH.  In general, you add about 1 pound of soda ash per 10,000 gallons of pool water to raise the pH by 0.1.

Conclusion

Raising your swimming pool pH is often needed, as the pH may drift downward over time due to a variety of reasons.  You need to test pH regularly, and correct pH as soon as possible, to avoid pool equipment damage and damage and staining to pool walls.

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