Why is polyphosphate added to softening process water?

Why is polyphosphate added to softening process water?

• A. To Prevent Recarbonation
• B. To Prevent Excessively Heavy Calcium
• C. To Control Recarbonation
• D. To Raise The pH

Answer: (B)

The main idea is that polyphosphate acts as a sequestrant for calcium in softened water. By binding calcium ions, it keeps them in a soluble form rather than allowing them to precipitate as calcium carbonate or other minerals. This prevents scale and deposits in pipes, tanks, and equipment after softening, especially as the water chemistry can shift (pH, temperature, and alkalinity). That’s why the purpose is described as preventing excessively heavy calcium. It doesn’t primarily raise pH or control carbonation, which is why those options aren’t the best fit.

The main idea is that polyphosphate acts as a sequestrant for calcium in softened water. By binding calcium ions, it keeps them in a soluble form rather than allowing them to precipitate as calcium carbonate or other minerals. This prevents scale and deposits in pipes, tanks, and equipment after softening, especially as the water chemistry can shift (pH, temperature, and alkalinity). That’s why the purpose is described as preventing excessively heavy calcium. It doesn’t primarily raise pH or control carbonation, which is why those options aren’t the best fit.