The organ that helps maintain water balance and keep pH equal to acidity is the kidneys.

Here's how the kidneys play a crucial role:

* Water balance: The kidneys filter blood and regulate the amount of water that is excreted as urine. This helps maintain the body's fluid volume and prevents dehydration or overhydration.

* pH balance: The kidneys filter out waste products, including acids. They can also adjust the amount of bicarbonate ions (alkaline) in the urine, helping to neutralize excess acids and maintain a stable blood pH.

While other organs contribute to pH balance (like the lungs), the kidneys are the primary regulators of water balance and pH in the body.