[Shop-talk] Water heater drain help

[Scott Hall]

Guys,

Got new water heater for house. Want to replace existing drain arrangement
with ball valve for better draining.

The fitting into the tank I think is probably not replaceable. But I could
replace the plastic plug and screw a fitting/ball valve into it. It looks
like this:

http://imgur.com/wn4DPQg

But I'm not sure what that thread is. It's not NPT--it seems to be about
twice as coarse as NPT.

I tried a 1/2" NPT spigot iftting I has here and it screws in, but it looks
like it might be cutting its own threads into the fitting on the tank,
which I think is Bad.

Anyone familiar with what that thread might be?

The plug's plastic so it won't rust, but it looks like it's just asking to
have those tiny holes clogs, or for the whole plastic plug to embrittle and
break. A nice ball valve with a big handle on it would be preferable.

Scott