Quote Originally Posted by MSSP View Post
They do make a tool for this. But by code you are not supposed to use Pex for the T&P line. You should call a Plumber.
As an inspector, I've always allowed the use of PEX for the T&P drain because it's permitted in the IRC. P2803.6.1 item 13 allows any material listed in Table P2904.5. PEX is not restricted because the temerature rating only applies to the matrerial when it's under rated pressure, that is, the limitation is set for a maximum temperature when operating at it's maximum pressure; and a drain is under no pressure at all.
As far as removing the T&P drain line, I would cut it off and use a new pipe on the new valve. (Not worth the trouble).