pH change in standing tap water.

[DrP]

We are in an area that has hard water.... however, it also seems quite aerated when it comes out of our tap. The pH when delivered from the tap is ~ 7.2 to 7.4. (higher than 7, presumably due to the hardness and chalkiness of the water). When left in a beaker or a closed container overnight the pH increases to 8.4 - 8.6. (this can be accelerated to a few by mins boiling it in a kettle)

 

 

 

We have a theory as to why this is, but does anyone know for sure what is happening? If so then please explain.

 

 

 

Our speculative reasoning: - the hardness of the water is causing it to be pH 8.6 instead of 7. Dissolved gasses and C02 in the water straight from the pipe cause the water to show a lower pH and bring it back down to 7.4. Overnight (or during a boil), dissolved C02 in the water leaches out and the pH rises back to 8.6. Seem reasonable?

 

Thanks.

 

 

 

[StringJunky]

We are in an area that has hard water.... however, it also seems quite aerated when it comes out of our tap. The pH when delivered from the tap is ~ 7.2 to 7.4. (higher than 7, presumably due to the hardness and chalkiness of the water). When left in a beaker or a closed container overnight the pH increases to 8.4 - 8.6. (this can be accelerated to a few by mins boiling it in a kettle)

 

 

 

We have a theory as to why this is, but does anyone know for sure what is happening? If so then please explain.

 

 

 

Our speculative reasoning: - the hardness of the water is causing it to be pH 8.6 instead of 7. Dissolved gasses and C02 in the water straight from the pipe cause the water to show a lower pH and bring it back down to 7.4. Overnight (or during a boil), dissolved C02 in the water leaches out and the pH rises back to 8.6. Seem reasonable?

 

Thanks.

 

 

 

That makes sense to me. Dissolved CO₂ creates Carbonic acid

[John Cuthber]

This might help clear things up

http://www.lenntech.com/ro/temporary-hardness.htm