Tankless water heater small leak, from drain valve?

[mrkapasi]

My aging parents just moved to a new home in the Mueller neighborhood of Austin, Tx, where record lows hit yesterday.

Many homes in the relatively young neighborhood have tankless water heaters and reported no hot water today due to the freeze, including my parents. I made it over there to take a peek and saw this small leak at what I *think* is the water drain valve. Am I right about that?

https://photos.app.goo.gl/83GnYTh42PFLtKuWA
Model Noritz NR981-OD

Is it likely an easy fix, maybe just requiring turning the unit off and replacing the valve seal? Or should I leave it to a plumber? I'm experienced with basic plumbing but little more.

By late afternoon hot water had returned to many taps but not the kitchen sink. I'll add updates as I hear more from my parents.

 

[mrkapasi]

Update 2/15 at 11pm:. Earlier this evening the kitchen sink hot water is running again.

 

[Twowaxhack]

Looks like it was leaking with the valve off too......

There’s a hose washer under that cap. You might could just tighten it.

That valve is not holding, probably freeze damage.

 

[mrkapasi]

Yeah, that makes sense. I suppose I should look into replacing the entire valve unit.