Basics of Swimming Pool Water Chemistry

    07/ 02/ 2015 1 Comment

    Swimming Pool Water ChemistryIf you own a pool, you are very familiar with the concept of having test strips or drops to measure the chemical levels in your pool.  It is a maintenance step to ensure that you have clear water that is sanitised and safe.  In this article, we will highlight the main components of swimming pool water chemistry that we test when you bring a sample to our stores in Ottawa.  We will also explain why they need to be balanced.


    Chlorine is the product that is ready to fight bateria and algea to keep the water sanitised.  Most pools are recommended to keep the levels between 1 - 3 ppm.  If you have a nature2 water purifier, it can be 0.6 - 1 ppm.  We have a seperate post about chlorine in swimming pools where you can read more.

    If your chlorine level is 0, then algea and bacteria can freely grow in the pool water.  If the chlorine level is high, it can cause irritation, dry skin, bleaching of hair, ect ect (depending on how high).  If you have a solar blanket, it can cause damage to it as well.  Chlorine is an oxidizer, so you must be careful.


    You can always refer to Wikipedia for the official definition.  In simple terms, it's a measurement of the acidity of your water.  Scale is from 0-14.  7 is neutral water. 

    The PH of the water affects not only impacts the safety of you jumping into the water, but it also impacts the reaction of every other chemical in the water.  If you have just filled the pool with fresh water, there is no need to worry.  What should be kept in mind, is that every chemical you do add to the water, if added in incorrect amounts, can shift the PH levels to unsafe levels.  

    If the PH is too low, the water literally becomes acidic.  It will cause red irritated eyes, skin irritation and may corrode your pool equipment as well.  Your water will usually be pretty clear... because algae is a plant and the acidity kills everything.  So... don't jump in ok?  

    If the PH is too high, this is also bad for your skin, causes itchy eyes and makes the chlorine much less effective.  We often see people come in and say the pool stays green even after add lots of chlorine.  This often is the reason why.


    Alkalinity is a measure of the stability of the PH.  If your Alkalinity is low, any substance you add with high PH will drastically affect the PH of the whole pool (example, chlorine).  If you add a substance with low PH, pool PH goes low (example, rainwater).

    If your Alkalinity is good, your PH will typically fall into place as well.  They work hand in hand.


    We measure the hardness (calcium) level of the water.  If the levels are too high, you'll see mineral buildup in the pool.  But the calcium actually provides a chemical protection to your major pool equipment, especially the heater.  A heater usually contains copper components or other metal parts in contact with the pool water.  Chlorine binds calcium first if it's available.  If it's not, it may bind to that heater component, causing corrosion.

    So this part is most critical when you have a heater.  

    Also, if your calcium level is very low, suds or "bubbles" may be more frequent when adding low concentration algaecides or having bathers with soap residues on their bathing suits.

    Copper & Iron

    We measure the copper and iron dissolved in the water because these substances are bad for your health, especially if swallowed.  What is important to note is that by testing for these chemicals, we can tell if something bad is happening to your equipment (like a heater).  These metals are introduced from:

    • The water source you added to the pool (which is rare)
    • The corrosion of equipment.
    • By directly adding copper or iron to the water (by using products like Copper Sulfate Algeacides)

    Note on Copper Sulfate Algeacides

    Some algeacide products on the market contain copper sulfate.  If you use this product, we will detect the presence of copper in your pool.  It's important to note that these product are highly effective at clearing algea from the water.  But the toxic nature of copper sulfate algeacide makes us NOT recommend it.   

    Optional Test: Phosphates

    In rare instances, people will have chronic cases of green water.  They added chlorine by the bucket and they still can't get rid of those algea.  Although it is quite rare, when we see this happen, we test for phosphates.  Phosphates are food for Algea and if high quantities are found in the pool, it will allow algae to grow really fast!  So in those cases that we find phosphates - we recommended a product called NO-PHOS to get rid of those pesky things. 

    Final Thought on Swimming Pool Water Chemistry

    Beautiful Pool with Proper Swimming Pool Water Chemistry

    I had a client once come into the store requesting us to make the pool water as natural as possible.  But there is one problem:

    If your pool was left to be natural, it would be a green swamp.  Algae, bacteria and bugs would make your pool their home.  In all honesty, there isn't anything that terrible about it.  Plenty of people swim in lakes with fish that can nibble at your feet.  But if you're like most people who get a swimming pool, you want it to be a controlled.  Just like drinking water, being able to reduce/eliminate the risks of any disease from water contamination is a really good thing.  It also helps if your swimming pool is not attracting all the bugs found when you are out in nature.

    So to that, we hope this helps you understand how swimming pool water chemistry will give you cristal clear water!