Then why don't you all fit a cheap water alarm, (maplins)
I even fitted one to my bath because my Boss (mrs) tends to put the bath on and go about other chores, and forgetting about the bath, after the second flood, I fitted the water alarm, now she can do what she likes because she always hears the alarm going off, fit one in your tanks.
You can extend the sounder for the van or trailer mount guy's, or even the guy's with tanks in the garage, so its in your house.
Just a thought.