She may be getting two, but he's gonna get the big one.

I wonder if they're both being fucked until he fills the tank
At least he'd have good motivation

Hearing her right next to him, begging for him to cum, right before giving another one of her orgasms to the machine

He hears a frustrated yet relieved moan, followed by the sound of her pussy, squirting against the machine's relentless penetration

He'd fill up that tank in no time~