What must be installed if a sink is situated near a mop sink?

When a sink is installed near a mop sink, it's essential to include an approved backflow prevention device to safeguard the water supply from contamination. This is crucial because mop sinks are often used for cleaning and may introduce contaminants into the plumbing system. In the event of a backflow incident, without a backflow prevention device, dirty water, potentially containing harmful substances, could siphon back into the clean water supply.

By installing an approved backflow prevention device, you ensure that the potable water supply remains protected and that there is a physical barrier preventing any cross-connection. This is a vital part of plumbing codes and regulations that aim to protect public health and maintain safe drinking water.

Other potential options, such as a trash disposal unit, a secondary drain, or a pressure regulating valve, do not address the immediate concern of backflow and contamination risk posed by having a mop sink near another sink. While those components may be useful for different reasons in plumbing systems, they do not fulfill the critical function of preventing backflow in this particular scenario.