How to Lower pH in a Saltwater Pool (Step-by-Step Guide)



Is the pH level in your saltwater pool always on the high side?

Don’t know what type of acid to use, how much to add, or how to add it without messing with the balance of your water?

This article will discuss what high pH is, how to lower the pH in your saltwater pool, and how to fix total alkalinity after (if it needs correcting).

What pH is Considered too High?

pH is measured on a scale of 1 to 14.

The lower the reading, the more acidic the water. Specifically, a pH level of 1 is very acidic, a pH of 7 is neutral, and a pH of 14 is very basic.

An optimal pH level for a saltwater pool sits between 7.2 and 7.8, so anything above 7.8 is considered too high.

The side effects of high pH become more severe the more basic the water becomes, so a small and temporary rise above 7.8 isn’t something to cancel your vacation over.

How to Lower pH In a Saltwater Pool

Here’s our 5-step process to lower pH in a salt pool using acid:

1. Start by Testing Your Water

It’s impossible to know how what to add (and how much) if you don’t know your starting pH and total alkalinity.

So, using a pool testing kit, start by getting a basic reading on your water. Liquid test kits are ideal as they’re often more accurate than testing strips, but you could also take a sample to your local pool store.

These numbers will be important in the following steps.

2. Figure Out Your Pool Capacity

There’s just one more number you need before we can calculate the right dosage of acid: your pool capacity or volume.

This is essentially how much water your pool holds, measured in gallons.

If you don’t already know it, you’ll need to measure the length, width, and depth of your pool, in feet. You can then plug those measurements into a pool volume calculator to get your capacity.

Before moving to the next step, you should know your starting pH and total alkalinity, as well as how many gallons of water are in your salwater pool.

3. Calculate the Amount of Acid You Need

Most pool owners use either muriatic acid or dry acid (sodium bisulfate) to lower pH, and some use sulfuric acid.

We strongly recommend using muriatic acid for saltwater pools because it’s the only acid that doesn’t add sulfates to your water, which, in excess, will damage your pool surfaces and corrode the coatings of your saltwater cell plates.

On average, here’s how muriatic acid impacts pH per 10,000 gallons:

  • 10 oz of 15% strength muriatic acid lowers pH by 0.1
  • 5 oz of 31% strength muriatic acid lowers pH by 0.1

While you can figure out a rough dosage based on those averages, you can also calculate a far more accurate dosage by combining your pool volume with your starting pH level and total alkalinity.

Simply enter all three numbers into this chemistry calculator along with your target pH, and take note of the recommended muriatic acid amount.

Important: Acid will always lower total alkalinity along with pH. This is an unavoidable part of the process and something we will correct later if your alkalinity drops by too much.

4. Pour the Acid into Your Pool

Adding muriatic acid to a saltwater pool is fairly straightforward, though wearing protective equipment such as gloves and goggles is still advised.

Here’s the safest way to do it:

  1. Grab your jug of muriatic acid and a measuring cup.
  2. Position yourself near an active return jet at the deeper end of your pool (this will help to circulate the acid)
  3. Holding the jug in one hand and measuring cup in the other, extend your arms over your pool water as far out as possible.
  4. Slowly pour the muriatic acid into the cup and tip it into the water when full
  5. Repeat this ‘pouring and tipping’ process until you’ve added the total required dosage.

Note: Contrary to popular belief, you do NOT need to dilute muriatic acid in a bucket before adding it to your water.

5. Perform a Final Water Test

Muriatic acid only takes a few minutes to work, but it’s worth allowing up to 15 minutes before running another test on your water.

During this time, it’s important to keep your pump on and return jets angled to promote circulation. You also should not be adding any other chemicals to the water before retesting.

Remember, you want your pH level between 7.2 and 7.8. If it’s still not low enough, you’ll need to add more acid.

Note: Don’t be alarmed if your total alkalinity has dropped too far. We have a section below on how to deal with that.

How to Fix Alkalinity (If It’s Now Too Low)

Muriatic acid will lower your total alkalinity alongside your pH level.

Fortunately, if your alkalinity is too low (below 80ppm) after adjusting your pH level, bringing it back up is a piece of cake.

Speaking of cake, you’ll be using baking soda (sodium bicarbonate) for this. Baking soda raises total alkalinity without raising pH by any meaningful amount, making it the ideal substance to pair with muriatic acid.

On average, here’s how baking soda effects alkalinity per 10,000 gallons:

  • 5 oz of baking will raise total alkalinity by 2ppm
  • 14 oz of baking will raise total alkalinity by 5ppm
  • 27 oz of baking will raise total alkalinity by 10ppm

As before, while these averages are good to know, the exact amount should be based on your current pH and alkalinity. You can get a far more accurate measurement using this calculator.

Acid is Your Friend

Rising pH is a problem with most pools, but saltwater pools are even more prone to high pH due to additional aeration caused by a saltwater generator.

Fortunately, lowering the pH level in your saltwater pool is easy; all it takes is a few simple measurements, a calculator, and a jug of muriatic acid.

Categories: Pool Care, Pool Chemistry