All of our levels are good in our swimming pool but why does our PH level keep going up?

Question

We add PH down to bring it down and it goes down but it keeps going up everyday.

Answer 1

Urine.  When I was a lifeguard we were always having to add soda ash to neurtralize the ph.

WAIT... you said the acid is too low... (high ph).  Now I'm curious....

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Here's what I found:  

Tendency for the pH to be permanently high (above 7.6).

Likely cause:

This is due to either (1) high pH of mains water (especially in hard water areas) or (2) to the use of alkaline chlorine donors such as calcium or sodium hypochlorite, or (3) to hardness salts being leached from new concrete or mosaic pools.

Solution:

The remedy is the same irrespective of which factor is at work here - correct the pH. To lower the pH, add dry acid at a rate of 1kg per 100 cubic metres (22,000 gallons) per day until correct reading is obtained.

For (1) and (2), consider changing to a low pH chlorine source to help achieve a natural balance between the high pH of the water and the low pH of the chlorine donor. stabilizerTrichlor is the obvious chlorine donor to choose. For (3), the difficulties with new concrete pools will clear up of their own accord given sufficient time.

Answer 2

To be sure I would need more info. Yes, if it is a new plaster pool then the pH will rise often for about a year but the rise will be less and less over time. If you have a salt chlorine generator this will cause your pH to rise because the generator produces small bubbles. When bubbles are released from your pool they are releasing carbon dioxide which causes a rise in pH. If you have water features such as fountains, jets, or waterfalls this will cause your pH to rise in the same manner as a salt chlorine generator because they produce bubbles. If your TA (total alkalinity) is high- above 120ppm- this will cause your pH to rise. I would suggest using muriatic acid instead of the granular pH decreaser (sodium bisulfate)- it is cheaper and more effective and will lower your TA as well if it is high. 11oz. of muriatic acid will lower your pH by .25 and TA by 4ppm for every 10000 gallons.

Answer 3

Let's see why your pH keeps going up.  The pH will naturally vary with temperature but the likely cause of it going up, towards 8.0, is the chlorine used has a pH higher than 7.6, normal pool pH.  Liquid pool chlorine, sodium hypochlorite has a pH of 13.  

Also additions of water sometimes affect pH since in Southern California our water is high in pH 8.0++ and Alkalinity.  Adding baking soda will increase Alkalinity and pH somewhat and serves to buffer (stabilize it or allow the pH to resist change) the pH and values in the 100-120 range are ideal.

Take a sample of your pool water to a pool supply house for testing.  They should see your TA is out of wack or not.

You're welcome!!