Ideas for driving an electromagnet with high voltage AC current from a PCB
Assuming you absolutely must use this specific pump and no other, the way I would do it is as follows:
Bring 120 V mains into the enclosure, but not onto the board; have it go into a pre-made and certified power supply (like one of these, for example) so you don't have to worry about dealing with mains isolation on your board. Then have the mains line also go into an off-board relay (I'd use one like this in an off-board relay socket), and then have your circuit switch the relay's coil voltage, which is a nice safe 24 volts (you can find 12 volt ones too if you want lower!), thus avoiding any need for mains voltage on your board.
This is not the smallest possible solution, and if you have space to put a DIN rail you can use DIN-mount PSUs and relays to make things a little neater, but this is how I'd go about solving this problem.