Can I plug the flow meter component into an existing Protect by LeakSmart Shut-off valve (formally called the LeakSmart Cut-in Valve)?

No, the flow meter component can only be used with the Protect by LeakSmart with Flow valve. Use the valve included with the flow meter in the Protect by LeakSmart with Flow kit. You will need to replace the old LeakSmart Cut-in valve with the new valve in the kit.