Q: Water hose leaking at firewall of 2012 ford focus

Typically, those are molded 5/8 inch ID rubber coolant hoses that are retained by either spring steel clamps or adjustable stainless steel worm drive clamps. Once you remove the hose, even to inspect it, it will not seal well when re-applied to the nipple. If you attempt to tighten the connection (if there is a worm drive clamp) to stop the leak, unless the connection was obviously loose to begin with you run the risk of crushing the steel or plastic nipple that the hose is attached to. Consequently, when faced with a leak such as this, the best practice is to remove the hose and install a brand new hose. If the hose is molded, you cannot use anything but a molded (preferably OEM in many cases) hose to replace it because if you use regular bulk heater hose it will collapse and then your heater core will not get circulating coolant. If you desire that this leak be repaired by a certified Mechanic, dispatched by YourMechanic right to your location, please request heater hose replacement and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.