Soda Ash pH increaser 40 k.  100% Sodium carbonate (Na2CO3) also known as washing soda, is a sodium salt of carbonic acid used for increasing the pH of swimming pool water 

• Powder form dissolves quickly and goes to work instantly
• Made with 100%  sodium carbonate
• Restores pool chemicals to proper and safe levels
• Helps prevent metal corrosion and plaster staining
• Creates safe and irritant-free environment for swimmers 
• Non-toxic, non-irritant.
• Store in any cool dry place.

Usage:

in 10,000 US gallons (38,000 litres)of  water - a typical domestic pool - 6 ounces (about 170 gr) of Soda Ash will raise the pH levels by around 0.2