John Guest Shut Off Valve 3/8" Push Fit x 3/8" Push Fit Genuine John Guest Shut Off Valve 3/8" Push Fit WRAS Approved Product Used To Turn Water Supply Off & On John Guest 3/8" to 3/8" Push Fit Shut Off Valve. Model number: PPSV041212W. For use with 3/8" Inch water filter tube. Use this handy device to provide a shut off facility to your water filter system. By simply turning the blue handle, you will shut off supply to your water filter or water cooler system. Otherwise known as a "ball-valve" the John Guest shut off valve is the most reliable and high quality with NSF certification (standard 51 and 62) and FDA approved material, guaranteeing safety with water and food application