Is it ok to modify a power socket to use one relay to control the phase and one to control the neutral wire?
[Edit] Another user points out this relay is unsuitable for switching 240VAC motors.
You only need one relay to cut the power to the pump. But you can use two if you want to be sure there's no live voltage at the other side of the relay when you switch it off. In continental Europe, for instance, it's impossible to know which line is neutral and which wire is phase.
In any case, be sure to connect the earth, always.
The relay appears to be unsuitable for controlling a 220 v motor. The manufacturer's specifications list inductive load ratings only for 120 volts.
You just need to open the circuit in order for the motor to turn off. It doesn't matter if you accidentally swap the Phase and Neutral as long as you open the circuit.
The relay rating seems fine, just Go Ahead with it. If you feel like, you can just have 2 Relays.
It will work just fine, both ways.
Note: Motors will usually have a peak current during startup that could go 10 times its actual rating. Make sure the peak lies within the Specs of the relay. Look up the specs of the motor.