What is the maximum total water hardness allowed in residential applications?

The maximum total water hardness allowed in residential applications is typically considered to be 3.5 grains per gallon (gpg). This standard is based on water quality guidelines that indicate levels above this can begin to cause issues with plumbing fixtures and appliances, leading to scaling and inefficient operation. Hard water, which contains a high concentration of minerals like calcium and magnesium, can result in the buildup of limescale in pipes, water heaters, and other appliances, which reduces their efficiency and lifespan.

In residential contexts, it's crucial to maintain water hardness at or below this threshold to ensure optimal plumbing performance and prevent damage. While lower levels of hardness are often preferred for skin and hair care, levels above 3.5 gpg may require the use of water softeners to mitigate these issues and provide better quality water for domestic use.