Tendency for the pH to remain low (below 7.2)

This is usually due either to low pH of water supply (especially in soft water areas) or to the use of acidic chlorine , such as trichlor

• Correct the pH. To raise the pH, add soda ash as directed per day until correct reading is obtained.
• Consider changing to a high pH chlorine source to help achieve a natural balance between the low pH of the water and the high pH of the chlorine donor. Dichlor is roughly pH neutral; calcium hypochlorite and sodium hypochlorite are high pH chlorine donors.

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.

To Remedy:

• The remedy is the same irrespective of which factor is at work here – correct the pH. To lower the pH, add dry acid as directed 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. Trichlor 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.