Are you saying you want to send the command from an X10 module of some kind rather than using a program saved on the CM15A or CM11A? If so, the only thing I can recommend is using a time delay relay and a Powerflash module (PF284 or PSC01). But, you'd also probably need a Universal Module (UM506 or PUM01) to receive the start for the timer. If it were me, I'd get a CM11A or CM15A and program it with AHP and then disconnect it from the PC since you want autonomous.
Alternately, you could get an Arduino and a TW523 (2-way) or PL513 (transmit only) module and a button. You could code the Arduino to accept the button push and immediately send ON to the pump. Then, delay 1 hour prior to sending OFF. This would be cheaper than the Power Flash/time delay relay/Universal Module option. It would be more expensive than the CM11A or CM15A option probably. The CM15A/CM11A option is the easiest and cleanest approach.