Within the Red Hat certification program, the RHCA is considered the most complete (and grueling) certification among the seven major Red Hat certifications. In fact, some equate the prestige of the RHCA to that of the Microsoft Certified Master and possibly the CCIE.
A plumbing fixture like a sink can not function properly without a sink vent. When a drain pipe drains it creates a negative pressure in the sink drain; the negative pressure will pull the water out of the p-trap of the sink that's draining and sewer gases can enter your home if a sink vent is not installed.
Question: The inspector who checked the home we're selling reported that the dishwasher needs an air-gap device on the drain line. The problem is that we have no place to install an air gap because the hole on the back rim of the sink is being used for the water purifier. Instead of an air gap, our handyman has installed a check valve in the dishwasher drain hose below the sink, but the home inspector says this does not comply with code. The handyman says air gaps and check valves are equally effective and that even a high-loop drain line can be used to prevent back-siphonage.