Heavy water leak from T&P Valve from water heater

[Ting Liu]

My water heater was replaced several months ago.  Then there was water hammering sound.  Later, the T&P valve started leaking heavily. Once I turned on the incoming water to the water heater, there was screaming sound and the T&P valve being pushed out and heavy leaking from the pipe.  I have replace the T&P Valve.  But still leaking heavily.  It's not dripping, but heavy leaking. BTW, there was no leaking issue with the old water heater.  Any expert recommendations? Thanks!