Pool pH Level: Why It’s Important (And How To Balance It)


by Rick Patterson

There are many facets to owning and maintaining a pool, and almost all of them start with your pool pH level.

Let’s go over everything you need to know.

What Is Swimming Pool pH?

pH stands for “potential hydrogen”, which represents the ability of a substance to attract hydrogen ions.

Basically, it’s the measure of how acidic or alkaline (basic) your water is – or in this case, your swimming pool water.

This is measured on the pH scale from 1 to 14, with 1 being extremely acidic and 14 being extremely alkaline. A pH level of 7 is considered neutral, as in neither acidic nor alkaline.

To put this in perspective:

  • Lemon juice has a pH level of 2 (very acidic)
  • Urine has a pH level of 6 (acidic)
  • Tap water has a pH level of 7 (neutral)
  • Seawater has a pH level of 8 (alkaline)
  • Bleach has a pH level of 13 (very alkaline)

The ideal pH level for your pool water is 7.4 to 7.6, or slightly alkaline.

Why Is pH Level Important?

The pH level of your swimming pool lays the foundation for the rest of your pool chemistry, so falling outside the recommended range can result in some pretty nasty side-effects.

Let’s talk about what they are:

It Can Damage Your Pool

If your pH level gets too high (alkaline or basic water), you’re looking at potential calcium scaling issues, which is a buildup of white scale or stains on your pool surfaces and even in your pipes.

Not only is scaling on your pool plaster a serious eye sore, but a buildup of scale in your pool’s plumbing will put strain on your filter system and other equipment, leading to circulation issues and even potential equipment failure.

On the flip side, if your pH level gets too low (acidic water), the water can become corrosive, eating away at the plaster, metals, grout, and even pool tiles. This can also lead to some stubborn pool stains.

Not even pool vinyl liners are safe, as they begin to lose color, become weakened and prone to tearing, and ultimately cause your pool liner to fall apart if left unchecked.

It Can Make Your Sanitizer Weaker

Pool water sanitizer, like chlorine, becomes less effective at killing bacteria, pathogens and algae as your pH level rises.

What this means is, as you move towards the higher end of the pH scale, you’ll need to add double or even triple the amount of sanitizer in your pool in order to achieve the same level of sanitation.

By the same token, lower pH will significantly increase the effectiveness of your sanitizer, meaning much less of it is needed. But go too low and you risk other adverse effects.

By adhering to the recommended range noted above, you’ll get the most from your sanitizing agent while still harboring a safe, clean and healthy environment for your pool.

It Can Be Harmful To Humans

It’s hardly a coincidence that the recommended pH level for your swimming pool water is about the same as a human tear.

This is where pool water will have the least wear on a swimmers body, and ensure the best possible water quality.

A pH level that’s too high causes dry, itchy, or “sticky” feeling skin, and even skin rashes. It also irritates the nose and eyes, similar to the feeling of getting shampoo in your eyes (we’ve all been there).

A pH level that’s too low has a similar effect in terms of skin irritation, stripping the natural oils from your body leaving you with dry, itchy skin. It also causes more severe eye irritation, such as redness, puffiness and burning of the eyes.

Note: These symptoms can also be caused by a buildup of chloramine or a high level of total dissolved solids (TDS).

It Can Make Your Water Cloudy

pH doesn’t directly make your pool water cloudy. Instead, it’s often a side-effect of the issues we’ve already covered.

The scaling caused by high pH water leads to circulation issues, which leads to cloudy water. The corrosion caused by low pH water creates debris, which also leads to cloudy water.

And it doesn’t stop there.

Since your pH level dictates the effectiveness of your sanitizer, improper pH can lead to poor sanitation. This turns your pool into breeding ground for various types of algae, bacteria, and viruses, and can also result in cloudy or green water.

What Causes Your pH To Change?

Sometimes, try as you might, your pH level can be thrown into the next dimension without so much as a warning signal.

Here’s why that happens:

Causes Of High pH

Rising pH is a problem most pool owners have to deal with on the regular basis, so don’t be alarmed if you find yourself in the same boat. It’s pretty normal.

However, if you find yourself with alarmingly high pH every time you test your pool water, there may be an underlying cause such as:

  • Total alkalinity is too high. Your pH level is influenced by your total alkalinity level, so if your alkalinity goes above the recommended range of 80 – 120 parts per million (ppm), it will also “pull up” your pH.
  • You shocked your pool. Shocking your pool introduces a large dose of chlorine to the pool water, and if you’re using a high alkaline type of shock, like calcium hypochlorite (cal hypo) granules, you can expect to see a bump in pH as well.
  • You used liquid chlorine. Unlike other types of chlorine, liquid chlorine  (sodium hypochlorite) has a high pH level of around 13, and using it will temporarily raise the pH in your pool.
  • You have algae. Algae blooms remove carbon dioxide from the water during photosynthesis, and this process slowly but surely raises the pH of your pool. It’s worth noting that algae thrives in a high pH pool, so the problem will get exponentially worse if left untreated.
  • Your saltwater pool. Salt systems by themselves don’t raise the pH of your water (the chlorine generation process is pH neutral), but the lack of acid from not using chlorine tablets will allow your pH to drift north. Our article on pool LSI explains this in more detail.
  • Your water features. More water movement means more exposure to oxygen, which causes water aeration (outgassing of carbon dioxide) and ultimately leads to higher pH.

Causes Of Low pH

On the flip side, a less common but equally as important aspect to understand is that of low pH in your pool.

A number of things can cause this, such as:

  • The outside world. These are natural organic elements you can’t always prevent finding a way into your pool, like grass, leaves, sand, insects, frogs, ducks, and everything in between.
  • People using your pool. Similarly, organic material like body oils, saliva, urine, deodorants, lotions and any other acidic substances that humans bring into a pool will reduce pH.
  • Rainwater. A little rain shouldn’t be a cause for concern, but since rain is acidic, prolonged heavy rain (or worse, a storm) can soon send your pool water pH plummeting.
  • Your water source. The pH of the water you use to fill up your pool may be more on the acidic side and may contribute to a low pH. This is common with well water, which is also unsuitably high in metals and calcium.
  • Your pool chemicals. Most pool sanitizers like chlorine and bromine are acidic, so using them in your pool will have a noticeable impact on pH. Shocking with a low pH shock, like trichlor, will have an even more dramatic impact.

How To Keep Your Pool pH Level Balanced

Finally, let’s talk about some of the things you can do to keep your pH level in order, and how to make any adjustments if necessary.

Regularly Test Your Water

The best way to know what’s going on with your pH and the rest of your swimming pool chemistry is to test it.

Not just at the start of the pool season. Not every once in a while. And not when something goes wrong. You need to be testing your pool water regularly and consistently.

When one aspect of your pool chemistry falls out of line, it creates a ripple effect that eventually impacts other aspects of your chemistry and ultimately upsets your pH level.

Here’s what you should be testing and aiming for:

  • Water pH should be between 7.4 and 7.6.
  • Total alkalinity should be between 80 and 120 parts per million (ppm).
  • Sanitizing agents (most likely chlorine) should be between 1 and 3 ppm.
  • Pool stabilizer (cyanuric acid or chlorine stabilizer) should be around 50 ppm if using chlorine products to sanitize.
  • Calcium hardness should be between 200 and 400 ppm. Ideally 300 ppm.

Any decent pool testing kit should be able to pick these up, whether it be using test strips, a liquid test kit or a digital test kit.

Stay On Top Of Maintenance

Regular testing allows you to figure out what’s going on with your water and your pool ahead of time. Regular pool maintenance prevents any anomalies from turning into potential problems.

In terms of water chemistry, this applies to everything we mentioned above, adding the necessary chemicals to keep them within the stated ranges.

Here’s how to adjust if needed:

  • Water pH can be lowered by adding muriatic acid or sodium bisulfate (dry acid) to your pool. pH can also be raised by adding sodium bicarbonate (baking soda) or sodium carbonate (soda ash).
  • Total alkalinity can be lowered by lowering pH (they are linked), and raised by adding sodium bicarbonate (baking soda) – which raises alkalinity more than it does pH.
  • Sanitizer level, assuming you’re using chlorine, the chlorine level can be lowered numerous ways but the easiest is waiting for the sun to burn it off. It can be raised by adding more chlorine, obviously.
  • Pool stabilizer (cyanuric acid or chlorine stabilizer) can be lowered by draining or diluting your water, and raised by simply adding more cyanuric acid. Keep in mind that most slow-release chlorine, like chlorine tablets, are already stabilized.
  • Calcium hardness can be lowered by draining or diluting your water or using a pool clarifier or flocculant to clump excess calcium. It can be raised by adding calcium chloride or using a calcium based chlorine, like cal hypo.

In terms of surfaces and pool equipment, regular maintenance encompasses everything from cleaning and backwashing filters, to vacuuming and scrubbing surfaces.

Keep Your Water Well Circulated

You could have Dexter’s laboratory in your pool, but if the water isn’t being circulated, you won’t see much benefit from all those chemicals.

It’s important to check that your water is moving through your pool filter system without restriction, and that the circulation cycle is optimized, helping to keep your chemistry (including your pH) in check.

Much of this ties back to proper maintenance, particularly when it comes to your pool pump and filter, as well keeping things like calcium scale from clogging up your pipes.

But there are a few other things you can do, including:

  • Installing a flow meter to check the flow of water
  • Installing some water features to keep water moving
  • Directing your pool jets to improve the overall flow
  • Checking your pump sizing is correct to move enough water
  • Making sure you’re running your pump long enough
  • Checking your water level is at the right level for the skimmers
  • Using a pool cover to limit contamination

Don’t Lose Your Balance!

Having a strong grasp of your pool pH level and the role it plays is the only way to truly master your pool chemistry, and keep your pool clean and healthy.

Get this right, and everything else becomes so much easier.

Categories: Pool Care, Pool Chemistry