I am changing a basement shower which is twenty years old. The old drain is attached to a cast-iron pipe, and it seems to be soldered together. The new drain is plastic. How do we adapt the new drain to the old pipe? (And how do we get the old drain off?)

Our hot water heater is about a year old. I realize it has a T&P pressure release valve on the top to relieve the pressure that builds up in it. Up to date, it has never released any pressure, until today. We had our gas turned off for 2 weeks, due to a new addition on the neighbor's house being built, then, yesterday, they turned all the water off and reran the water lines from the well, through the big house and back to ours. Supposedly, it was to have increased water pressure, which, our house didn't seem to have a water pressure problem. Now, when I turn on the water to the hot water heater and turn the heater on, the valve goes off continously. Is this due to a clogged tube in the water heater? I tried to flush it, because while everything was off for 2 weeks, except cold water, the water softener was also off. We have very hard water. Any ideas of what is going on???? Also, it releases the water pressure when the water it turned on to it, without the water heater even turned on. [This message has been edited by cubby121 (edited July 29, 2000).]