Plumbing – How to protect plumbing to an outbuilding from freezing

EDIT: I bought a PVC 1" barbed to 1/2" threaded fitting and a kit with a 2' >braided hose and a shutoff valve. So I'll try bringing the 1" poly up to under the >sink, and then use these bits. We'll see...

I would have probably done that as well (caveat: I am only vaguely familiar with poly, aka "Polybutylene." I have never used it for a job or even had to replace it...It's very uncommon here in northeast Ohio. ) although at first thought, I'm not sure whether it makes a difference to put the Poly to PVC underground or above. I'd also probably put that poly above the sink, then put the Poly to PVC fitting > then the shut off valve, and finally, the braided hose to the faucet..

(FWIW, I'd still use copper, but my boss is extremely old-school..).

You need to find the main shut off valve in the road, side walk or somewhere on or near your property. They are usually placed in mini manholes with easy access:

But if you're unlucky you will need to get some building plans and try to find where on the plans the supply pipe runs and find the valve at the connection point to the main supply. In most cases it will be near the connection point of the main supply:

but if its not, or if you struggle to close it call your council to help you. You don't want to break that!

NB

It is easy to snap these valves- if its rusted badly apply (known as WD-40, LN-40, HT-40) spray oil based rust release (spray leave an hour try again.. repeat a few times), TAP the valve with a hammer (!TAP!, do not whack it, to help release the valve. Also, usually opening the valve slightly helps to release it then try to close it.