[![7 Day History showing Spikes After Winterizing](https://i.stack.imgur.com/cd5Ro.jpg)](https://i.stack.imgur.com/cd5Ro.jpg)We are getting spikes in water pressure, measured at the main feed to the house, starting yesterday when the outdoor sprinkler was shut and winterized. I have a backflow preventer that is tested annually.

Similar spikes happened last winter, but I didn't see the link until now.

The pressure gets reset when a toilet or other appliance runs, causing pipes to rattle, then the pressure builds again.

I can't understand why shutting the sprinkler would affect pressure in the house.