August 26, 2023

Swimming Pool Water Tests Explained

pool water testing explained

Making Sense of your Water Test

swimming pool water test

When you get a swimming pool water test from a pool store, you may want to know what is actually important before you spend money on chemicals you may or not need. I am disappointed to see some of the unnecessary chemicals pool stores are selling their customers. Below I have outlined the key components of a swimming pool water test.

*Side Note, “opening and closing kits” are nice to haves not need to haves. Adding chlorine (10L) when you open or close a pool is often all you need.

The most important readings of a swimming pool water test are:

  1. Chlorine levels
  2. PH levels
  3. Alkalinity levels
  4. Stabilizer levels
  5. Calcium levels (particularly for concrete pools)
  6. Salt levels (salt water pools)
  7. Copper levels

Chlorine / Stabilizer

For a standard chlorine or salt water pool, the ideal range for chlorine is between 1-3ppm. Ideally you want as little chlorine in the water as possible while still being able to keep the water clear. When it becomes hot in July and August, chlorine will burn off quicker then when it is cool. Remember that when setting your salt cell or chlorinator. Ideal range on your swimming pool water test would be 1ppm during 20’C and 2ppm in +30’C weather.

Chlorine and stabilizer are connected to each other. Think of stabilizer as a sunscreen for chlorine. Stabilizer is added to slow down the chlorine being burnt off by the sun / hot weather. *PLEASE NOTE* People who use chlorine pucks (in a chlorinator or floating dispenser) there is stabilizer built in to the pucks and you DO NOT need to buy a separate container of stabilizer. The amount of times I have seen pool companies sell stabilizer to people using chlorine pucks is shocking.

If you have a salt water pool you will need to add stabilizer to help from having the chlorine burn off too quickly.

Another important reason to keep an eye on stabilizer levels of your swimming pool water test is if they get too high you can have a situation where your pool water is in a “chlorine lock” meaning the stabilizer is so high no chlorine is burning off. The only want to fix this is to pump water out of the pool (out the backwash line) and add fresh water, which is bad for the environment and costs you money refilling your pool.

PH / Alkalinity Levels

PH levels of your swimming pool water test tells you the acidity of the water. The PH level can change from things like rain or when oils get into the water (caused by people swimming with sunscreen or tanning oil). It is very important to keep the PH in range (7.2-7.8ppm).

The 2 main reasons

  1. If the PH moves outside of the recommended range on your swimming pool water test, the water you are swimming in is acidic and not safe (especially for young kids).
  2. If you have acidic water flowing through your pool system it can corrode out your heater potentially causing $1000’s to replace. In addition to that if your heater starts to corrode, you can get metal stains on your liner costing even more to fix.

Alkalinity (ideal range is 80-120ppm on your swimming pool water test), like stabilizer is like sunscreen for the PH. It protects the PH when it rains by acting as a buffer where it lowers instead of the PH. *IMPORANT NOTE* when you add Alkalinity booster, it will also increase the PH. For example if the alkalinity and PH are both low adding an alkalinity booster will increase both alkalinity and PH meaning you should never really need to add PH+ (when the alkalinity is low PH is often also low). Many pool companies will sell an Alkalinity Booster AND PH+ which usually a big “money grab.” I have maintained 1000’s pools over 8 years and cannot recall a time I had to add PH+


Selling calcium is one of the most common instances where I see pool owners being ripped off. For the most part the only time you need to worry about calcium levels is if you own a concrete pool (you don’t have a liner). If you have a salt water pool you should also be aware of your calcium level but it is not critical like chlorine / PH. Alternatively if you have a vinyl liner pool and use a chlorinator there is no reason to ever buy calcium.

Salt Levels

If you have a salt water pool you need to add salt in order for the salt cell to generate chlorine. Different types of salt cells need different levels of salt in order to work well. It is important what type of cell you have so you can adjust your salt levels properly. As a general rule, 1 bag of salt (44lbs) should bring the level up 500ppm on a standard size pool (60,000L)


Copper is something that is unusual to find in a well maintained pool. Most of the time if copper is in the water it is because the PH has gone out of whack and corroded out the heater. You can avoid this by following the instructions above by keeping your water balanced.

Bonus Section: Phosphates

If over the course of the summer you find you cannot get your water clear but your chlorine levels are in range or high, often times the culprit is high phosphate levels. Phosphates are common in pools that have a lot leaves falling into them from trees nearby. They are essentially what we call “food for algae.” As long as there are phosphates in the water you will have a difficult time getting your water clear. If this is happening to you make sure you ask your pool store to test for phosphates to see if they are a problem.


It is important to check your water weekly or at least bi weekly. In doing so you can keep your water balanced and avoid serious problems (unsafe swimming conditions, corroded out heaters and metal stains). Remember pool stores will try to sell you things you may not necessarily need, if you focus on keeping your Chlorine, PH, Alkalinity and Stabilizer in range, you will avoid a lot of bigger problems down the road)

Proud Memberships & Affiliations
Crush Pools Logo
Crush Pools proudly provides expert pool maintenance and servicing in Oakville, Burlington, Milton, and Mississauga.
+1 (905) 580-4741
© Crush Pools Inc., 2021. All Rights Reserved.
Design & Development by Oake Marketing.
linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram