Thanks for scaring the sh!t out of me, people
Off to Home Hardware tomorrow to load up on these things, for toilets and dishwasher at least. In going over the on-line -ve reviews, most people complain of false shut-downs due to irregular / spiky water pressure, or for extra-thirsty appliances like washing machines. I'd like to replace the cheezy Mattamy shut-offs on the washer lines and hot water tank with for-real ball valve shut-offs, and get into the habit of turning those off when not in use / away.
Also, I was not aware of that shut-off upstream of the water meter, never noticed it before! We keep our main line open when away, as we rely on pet sitters who may need the water on.
Thanks all,