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Have you ever wondered what consists in your pool’s water? Anything that is not pure H2O would be called TDS or total dissolved solids. Over time impurities accumulate in the pool’s water from minerals, calcium deposits, and algae blooms that begin to directly affect the pool. Almost everything can cause the TDS to rise, including; swimmers, leaves, dirt, natural stone, impurities from the air, landscape chemicals, disinfectants necessary for safety, landscape run-off, and evaporation which leaves all the non-water molecules behind. Just like mixing sugar in water, this is not necessarily something you can see directly in the water, but something you can feel and see affecting your pool’s plaster/structure. 

Here are some images from excessive TDS precipitation:

Calcium deposits – A from natural stone can increase the TDS.
Copper – from imbalance increasing dissolved solids.

Iron deposits
Here are some images of contributors to excessive TDS: 

Dogs/animals – Contributor
Rain – Contributor especially when if falls through trees above the pool.
Landscape runoff (Most common after rain)– Contributor
Natural stones leaching minerals and lime- Contributor 
Dirt/leaves – Contributor

Now how can we resolve having high TDS in our pool? A partial drain is normally the best and most cost effective solution! Partial drains are a normal part of pool maintenance and normally need to be performed every 1-3 years. It consists of removing a percentage of the old water from the pool and refilling with fresh tap water. This will lower impurities that accumulate in the pool’s water lowering the TDS. 

When doing a drain of the pools water, we do not advise draining more than 70% as some structural risks can arise when all weight is removed from the pool. It is best to perform this service before the cold weather weakens the plaster/surface, increasing susceptibilities such as tannins from leaves which can change the color of the plaster. For our customers that prefer best practices, in regards to comfort, aesthetics and surface longevity, we recommend performing this partial drain each year. Enjoy your fresh pool water! It feels so much cleaner when you get out of the water!!

You will experience the following benefits with your fresh water:

Hope this tip helps you keep your pool looking and feeling great!!


Noah Ullmann