Magnesium may affect the palatability of the water. Hard water will form a scale on plumbing fixtures. Sulphates - Sulphates have a laxative effect on birds and can cause wet litter if concentrations are greater than 500 ppm. Birds may build up a resistance to this effect. Greater than 3000 ppm is unacceptable for poultry.
Nitrites are the more dangerous of the two compounds.
In large quantities they will affect the capability of blood to carry oxygen and can be toxic. The recommendations for maximum nitrate concentrations varies. Some indicate that concentrations of less than 300 nitrate nitrogen should be tolerable for poultry, while others suggest a maximum of 50 ppm. Iron - Iron in water may stain equipment and laundry, and affect the taste, but is not generally considered a health risk for poultry. Iron bacteria may block pipes and drains, but are not directly a threat to bird health.