SylvanLMP
OK easy one here.
Want to find out if this type device is leaking GET a hose bib cap and cap the outlet.
Turn on the water supply and LISTEN no sounds means no leaks TA DUM
Now find the closet isolation valve shut it disassemble this valve remove the long valve stem as per manufacturers directions.
Get “Key grease” and lubricate the spindle threads completely look inside the valve opening with a flash light Or have someone open the valve and then close it to flush out any debris or particles stuck inside, reassemble valve and this should allow it to function as good as new. 
