Pool Alkalinity - Why It's Important and How to Get it to Normal

One of the most common topics discussed about swimming pools is pool alkalinity. In this article we'll be looking at just what exactly it is, why it's important and tips to deal with it if it's too high, or too low.

Pool alkalinity, also known as total alkalinity, is the measurement of how much alkaline substances are in the water. The normal range that we'd like to keep this at is 80 and 120 parts per million (ppm). This is because when it's in this range it stabilizes the pH levels of your pool water effectively preventing sudden pH changes.

Pool Alkalinity is Too Low:
If the range goes less than 80 ppm, we're going to be dealing with some troublesome problems if it's not corrected soon. At this level, staining, metal corrosion, burning eyes, and the water turning green are all common problems with a low level of alkaline.

To raise this level back to normal, we use sodium bicarbonate. Typically the amount we add is 1 kilogram per 50,000 gallons of water, and then only once every 4 days. This is the only chemical which will allow us to raise the TA without having too much of a pH change.

Pool Alkalinity is Too High:
When the alkaline level raises above 120 ppm we have an even different set of problems including: cloudy water, chlorine inefficiency and pH difficulties.

In order to effectively lower the TA back to a range that's desirable we need to take significantly more difficult steps than if the TA were too low.

First, our filter must off. Next, we begin to add either hydrochloric acid or dry acid at the deepest end of the pool. The amount needed depends on how much water is in the pool.

The best approach I've personally found with this is to first begin by adding enough acid to bring your pH balance down to 7.0. Then, let the pool sit for awhile until the pH climbs back up to around 7.2. Repeat this process until your pool alkalinity is within normal range.