My town doesn’t allow polymeric sand so I have to use regular masonry sand. It hasn’t affected the stability of the pavers, but pulling weeds all summer is kind of annoying.

Maybe you use plain sand now and come back and do it when it’s warm.

There are several. I have one as I mentioned in my comment: it’s called a Phyn Plus. It works with and without sensors. I have some in strategic places like under the water heater.

It actually caught a leak, although it wasn’t from the plumbing. It was rain getting into the chimney and dripping into a puddle in the boiler room that set off one of the sensors. I like the cable-style sensor they have – it’s like a 4-foot-long headphone cord, but the whole length is a water sensor, so if any part gets wet it goes off.

Cutting a pipe and adding a valve is a really simple thing and should only be expensive to the extent that any plumbing job is expensive.

I would specifically ask for a quality 1/4 turn ball valve - there’s no point in cheaping out on that part when you’re mostly paying for labor. And as long as you’re doing that, you probably want two of them. For the same reason the city doesn’t want you touching theirs, you should have a shutoff that you actually use when you need to do plumbing work in the house, and one before that that you never touch unless it’s an emergency and you can’t shut off the other one.

For a bit more expense, you could consider an automatic shutoff leak detector. I have one called Phyn that keeps track of water usage, tests for pressure drops every night, and detects unusual flow patterns and can automatically shut it off.