Why is pH Important for Swimming Pools?

May 21, 2019

Why is pH Important for Swimming Pools?

Many of our customers often wonder why pH is so important for their swimming pool.  Afterall, it always seems to be high, and can sometimes be difficult to maintain.  Here is why pH is one of the most important aspects of keeping a pool (or spa) safe, clear, and comfortable.

Water Clarity

Your swimming pool is part of your yard, and chances are you want to keep the water looking pristine, to compliment the rest of your yard.  When water goes hazy, murky, or just flat out hazy, pH is one of the first places we look at.  When your pH is in range, your water tends to just look better.  For pools who run higher levels of Total Hardness levels in their water (Calcium Hardness), pH becomes even more important for maintain water clarity.

Your Pools Equipment and Surface

Both high and low pH levels can damage your equipment and swimming pools surface.   Higher pH levels cause lead to scaling.  Constant high pH can also age your liner quickly.  With low pH, you might begin to see corrosion on your pools surface, ladders, pumps, and any other pool equipment.  Your liner may also begin to wrinkle, and depending on your chlorine levels, your liner may begin to fade.  Concrete swimming pools can experience etching with low pH, and this can be an extremely expensive repair.  pH is vital to keep in check, to protect your investment.

A Comfortable Swimming Pool

Acidic water (low pH) makes swimming uncomfortable and sometimes harmful to people.  Depending on your chlorine levels, you might see bleached bathing suits.  You’ll also hear about swimmers’ eyes stinging, and this low pH level can be harmful to the nasal cavities.  Swimmers’ skin might also feel sticky, dry, and itchy, and their hair might feel brittle.  Most of these factors are also in play if pH gets too high.  Keeping your pH within the recommend parameters can go a long way for your friends and family’s comfort and safety.


Most people use chlorine, and chlorine’s effectiveness as a sanitizer is completely tied to pH.  Salt is chlorine, or at least it’s converted to chlorine.  One of the by products of chlorine production with a salt system is Sodium Hydroxide (Lye), which has a pH of around 11, so salt pools should pay close attention to this, as they may find they have to make more frequent adjustments.

We recommend that you keep your pH of your swimming pool between 7.2 and 7.6, where 7.4 is the most ideal level you can achieve.  Always pay attention to what your swimming pool specifications are on equipment (e.g., your heater may recommend a stricter level of 7.4 to 7.6).

A pH lower than 7.2 will see better disinfection rates from their chlorine, however as mentioned above, will cause issues with your pools equipment and the comfort (and safety) of your swimmers.  A pH greater than 7.6 will see a massive drop in chlorine’s ability to disinfect the water.  A pH of 8.0 for example, has chlorine that is only roughly 25% effectively (At 8.5 that drops to under 10%).  This poses a serious health issue and should always be taken extremely seriously.

We should also mention that Hot Tubs have a lot of aeration (jets, bubbles, and air) and will see pH increase more rapidly.  Because most Hot Tubs tend to be covered when not in use, Bromine is often used, and is more tolerant to higher pH levels.  This topic is beyond the scope of this article, and will be covered in the future.

How to Raise pH

Most people buffer pH with Alkalinity (Sodium bicarbonate).  This prevents pH from dropping rapidly, and causing serious equipment damage, but at the same time, the addition of Alkalinity raises the pH in the swimming pool.  Sodium Bicarbonate has a pH of roughly 8.4, so when adding it, you will typically see a pH increase, and is why we tend to raise Alkalinity first.  If your Alkalinity is already within its recommended range, then you can use a pH increaser (Sodium carbonate).  Note, for large additions of Alkalinity, it’s best to raise the Alkalinity in multiple doses.  Never raise Alkalinity more than 40 ppm in one dose.

How to Lower pH

Most of the time, you’ll find that you need to lower your pH, rather than raise it. This is typically done with pH Minus, however some people choose to use Muriatic Acid.  Either option will work, but just be extremely cautious with Muriatic Acid, as it can severely burn and/or blind you if it splashes.  For this reason, we typically recommend pH Minus, but regardless, always follow the product’s directions and cautions.  Also note, when you lower your pH you will also be lowering your Alkalinity levels, which again, is why we tend to start with making sure Alkalinity is balanced first.

Is there anything I can add to help with the pH Struggle?

Yes, for Hot Tubs, we have a few products you can add that will “lock in” your pH, so you will not have to fight with them as often.  They are sensitive to Calcium, so it is best to add these types of products when you are first filling up your water, and your water source must be low in Calcium.  (These products essentially replace the need for Calcium)

For Swimming Pools, we have a product as well, and these products have many extra benefits.  These products are not calcium sensitive, and last the life of the water, only requiring top-offs once or twice a season, depending on how often you waste water with your swimming pool (Backwashing, Splash out, etc.).  These products should greatly reduce the amount of pH balancing, and therefore Alkalinity balancing you find you must do throughout the season.

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