According to regulations, the minimum pressure in all water distribution systems should not be less than?

In water distribution systems, maintaining adequate pressure is crucial for ensuring that water can reach consumers effectively and safely. The minimum pressure standard established by regulations is typically set at 20 psi. This pressure level is considered sufficient to allow water to flow effectively through the system and to maintain an adequate supply at service connections, especially during peak demand times or emergencies such as firefighting.

While lower pressures can still deliver water, they may lead to issues such as reduced flow rates and increased vulnerability to contamination, particularly if the system experiences negative pressures. Therefore, 20 psi serves as the benchmark that balances safety, accessibility, and reliability in water distribution.

The other values in the options tend to either not meet the minimum standards required for effective service delivery or exceed practical requirements, pointing to why they are not the correct answers. Maintaining pressure below this established threshold could compromise service quality and reliability for consumers.