Which of the following is used to de-lime a hot water tank?

Muriatic acid, a diluted form of hydrochloric acid, is commonly used to de-lime hot water tanks. Over time, minerals from hard water can accumulate in the tank, leading to scale buildup. Muriatic acid effectively dissolves this limescale due to its strong acidic properties, making it a suitable choice for cleaning hot water tanks.

The use of muriatic acid involves precautions, as it can be hazardous if not handled properly. It is essential to monitor the effectiveness carefully and neutralize it appropriately once the de-liming process is complete to avoid damage to the tank or plumbing system.

The other substances mentioned are not typically used for de-liming hot water tanks. Ammonia solution could have cleaning properties but does not effectively dissolve limescale. Bromide acid does not serve as a common cleaning agent in this context. Tri-sodium phosphate is typically used for cleaning and degreasing but is not effective for removing mineral deposits found in hot water tanks. Therefore, muriatic acid stands out as the most effective and commonly used option for this purpose.