So after cleaning up a mess this morning my wife informed me the hot water wasn't working at the sink. The following ensued (By the way the water heater is in the attic and its 1 degree in Oklahoma):
1) Used a hair dryer to heat up the supply valve which was frozen open, eventually freed its function
2) opened the relief valve on the water heater, heard gurgling for a while and sounds as if it was starting to fill
3) Eventually saw a droplet come out the relief and saw increased flow at the sinks (increased as in small trickle)
4) Followed the air lock procedures by back flushing with the cold water supply into the hot, all sinks flowed fine
5) Flow would eventually trickle off again, but the flow was hot which tells me the water heater is working and thus all lines should be free of ice (Pex piping btw)
6) Worth mentioning no flow issues on the cold side, only exposed cold piping is in the attic where I encountered the frozen valve.

This all leads me to believe that theres still some ice in the cold supply to the water heater reducing its supply pressure and air locking the system repeatedly.

Any suggestions of the DIY style? Most everything else says call a plumber. Maybe I should just hold open the relief till the flow breaks up the ice in the supply?

 

OK so maybe this will help someone in the future avoid a plumber.

Turns out it was a supply issue causing the air lock. After I heated up the pex with hair dryers the flow restored. Rather then run to the faucets and back repeatedly I just opened the relief until flow reestablished.

 

That was a thoughtful installation.

Here in NJ there are condensing furnaces installed in attics.

Usually once you get a trickle..... just letting the faucets trickle will allow the incoming water to unthaw the pipes. The other thing is to raise the house heat substantially. Absolutely no setbacks in cold times.