Here’s a tip to file under Why Didn’t I Think Of That?!.
Do nice things!
While your girlfriend/boyfriend/spouse/partner/mate is out running errands,
Run a hot bath. Hot. That water might be sitting for while.
Go to the kitchen and get out the big pots.
Fill the pots with water and put them on the stove.
Put a couple of buckets or larger containers on the counter and/or floor.
Scatter towels all around the kitchen.
Open cupboard doors.
Make sure the TV is off upon arrival.
If you can hear the person returning, turn on the burners on the stove.
Pro Level: Turn on a timer on the microwave.
(Side note: If said partner makes a quick appearance and says, “I’ll be right back”, turn off the timer, so that they don’t think you’re timing them to see how long it’s been before they return.)
They walk in and wonder what is going on.
You explain that you ran a hot bath and have been keeping up with it all day, so much so that you’ve run out of hot water in the entire house. You’ve been boiling water and lugging it to the tub to keep it hot for them. Awwwww.