What Happens if pH is Too High in a Pool? (5 Nasty Side Effects)



Ever wondered what happens when pH is too high in a pool?

This article will explain what classifies as high pH, what happens when your pH begins to rise, and whether or not it’s safe to swim in high pH pool water.

What Is “High” pH in a Pool?

The ideal pH level in a pool is somewhere between 7.2 and 7.8, or slightly 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)

If the water in your pool is at the upper limit of that range or just slightly over, it’s fair to say the pH of your water is too high and it needs to be lowered.

Note: Saltwater pools tend to have a higher resting pH level so it’s more acceptable for the water to be near the upper limit.

What Happens if pH is too High in a Pool?

Water chemistry issues can start to show even with a slightly raised pH level, but the effects become more pronounced as your pH drifts higher.

Here are 5 side effects to be aware of:

1. It Makes Your Water Cloudy

High pH can make your water cloudy because it changes the LSI of your water.

Put simply, a higher pH causes the dissolved calcium in your water to fall out of solution, which makes your water appear cloudy.

This is also sometimes referred to as “calcium clouding”.

In fact, the more calcium you have in your pool (or the higher your calcium hardness level), the more cloudy your pool will become as the pH level rises.

The same effect is often seen with new plaster or newly replastered pools because plaster is a huge source of calcium hydroxide for starved water.

This additional calcium can significantly raise the calcium hardness level and ultimately lead to cloudier water.

2. It Scales Your Surfaces and Equipment

Calcium scaling is a white, chalky substance that can build up on your pool surfaces and pool equipment, especially along the waterline.

In extreme cases, calcium scale can even compromise your plumbing and filtration system, restricting flow and affecting the circulation of your water.

While having high calcium hardness is an important factor, the real driving force behind these pool stains is actually high pH water.

Again, this has everything to do with LSI.

Without getting too much into the chemistry, as the pH of water increases, water requires less calcium. As a result, the excess calcium falls out of solution and deposits itself wherever your water makes contact.

This is why even moderately hard water can cause scaling when the water pH reaches a certain level.

3. It Weakens Your Sanitizer

Chlorine is most effective when the pH of your water is somewhere in the ideal pH range for a pool (7.2 to 7.8).

This is where chlorine has the most “punch” in terms of sanitizing power, but as the pH of the water moves up, this sanitizing power begins to diminish.

The effects of this are small at first, so a little boost in pH won’t have much impact on your sanitizer. However, a large increase in pH can have a crippling effect on your chlorine’s ability to sanitize.

When this happens, you’ll begin to notice your water looks dirtier than usual, and there’s a good chance algae will start to take hold since your normal dose of chlorine is now too weak to contain it.

There is a caveat, though.

High pH has far less impact on the sanitizing power of chlorine when cyanuric acid (stabilizer) is also present in the water, so if you do use stabilizer or stabilized chlorine, it won’t be as inhibited by changes in pH.

4. It’s a Little Harsher on Your Skin and Eyes

It’s not surprising that pH would irritate your skin and eyes, but this one isn’t as significant as you might think.

Considering tap water can have a pH of over 8, it would take an extremely high pH level before any ill effects are felt from high pH – well above the ideal pH range for a pool at 7.2 to 7.8.

In fact, unless you’re unusually sensitive to changes in pH, you would need to see a pH reading of more than 10 for it to be a cause for concern.

What’s more, eye irritation from swimming is often wrongly attributed to high or low pH water, but the cause is far more likely to be excessive chloramines (combined chlorine) in the water. This is why regular shocking is advised as it suppresses the natural build-up of chloramine.

Overall, while this is a side effect of high pH, in most cases it’s so subtle you really don’t need to worry about it.

5. It Makes Your pH Harder to Adjust

pH and total alkalinity are very closely related, so when your pH level increases, so eventually will your total alkalinity.

If you know your pool chemistry, you’ll know that total alkalinity is a pH buffer that protects the pH level from wild fluctuations.

This is useful for keeping your pH level within the ideal range, but when your pH level and total alkalinity are both too high, this buffering effect can very quickly start to work against you.

As you try to lower the pH by adding acid, the alkaline substances in the water absorb those changes first, which means you have to add even more acid in order to make a dent.

Can You Swim in a Pool with High pH?

Technically, yes.

For most people, the pH of your pool water would have to be extremely high (above 9) for the water itself to be considered remotely hazardous.

In reality, it’s the knock-on effect that high pH has on your sanitizer that poses the greatest risk to your health.

If your chlorine is unable to work effectively for an extended period, it may allow algae and other contaminants to wreak havoc on your water, and you certainly don’t want to be swimming amongst those.

Overall, a small but temporary upward shift in pH shouldn’t stop you from enjoying your pool, but if your pH level is elevated for several days or weeks, well… it’s probably not worth the risk.

What Causes pH to Get Too High in a Pool?

We wrote an entire article on what causes pH to rise in a pool and another one specifically for saltwater pools.

Here’s the summary:

  • You shocked your pool
  • You accidentally used a pH booster
  • You used high pH fill water
  • You have pool algae
  • You have water features
  • You have a saltwater pool
  • You replastered your pool
  • Your alkalinity is high

Is It a Bird? Is It a Plane?

No, it’s your pH level.

It’s not uncommon to see your pH level flying high, but regular testing and quick adjustment of your water will see you never have to deal with the full force of these side effects.

Categories: Pool Care, Pool Chemistry