What is the water demand of a shower head in a plumbing system?

The water demand of a shower head in a plumbing system is typically around 2.5 gallons per minute (gpm) based on modern efficiency standards. However, certain high-flow or older shower heads can use more water. In the context of the question, the option of 4 gpm aligns with the higher end of standard water flow rates for older or non-regulated shower heads that may not meet the latest energy efficiency guidelines.

The accuracy concerning water usage will depend on the type of shower head installed: newer models are often designed to conserve water and are usually limited to 2.5 gpm or lower. Therefore, while 4 gpm can represent some older or more powerful shower heads, modern standards encourage lower flow rates to promote conservation. Thus, while the identified option is not the most efficient when viewed through current standards, it does represent an understanding of historical or older models that could be in use, making it a potential selection in some contexts related to plumbing systems.