Final answer:
To address fixtures requiring more than 15 psi of water pressure, the water pressure should be increased. This ensures that the fixtures function properly.
Step-by-step explanation:
When fixtures and/or fixture fittings are installed that require a residual water pressure higher than 15 pounds per square inch, the appropriate action would be to increase the water pressure to meet the requirements of the installed fixtures. Not doing so might result in improper functioning of the fixtures or fittings.
Considering the problem related to water pressure as highlighted in the prompt, it's critical to understand that water pressure can fluctuate due to various reasons such as heavy use during peak times.
When resistance is constant and the flow rate through a hose decreases, it indicates that the water pressure being supplied to the house has also decreased. The relationships between flow rate, pressure, and resistance are fundamental principles in fluid dynamics, affecting the design and functionality of plumbing systems in engineering.