A gate valve assembly is disclosed that may be installed in a pressurized pipe or conduit. The gate valve assembly includes a nozzle that is connected perpendicularly to the pipe. The nozzle includes a distal end, a proximal end and a through passage extending therebetween. The through passage includes a proximal portion with a circular cross-sectional profile for sealingly engaging a wiper seal disposed on a valve cartridge. The passage also includes a distal portion with a non-circular cross-sectional profile that complements a non-circular cross-sectional profile of the cartridge. The non-circular cross-sectional profiles of the cartridge and passage prevent the cartridge from twisting or rotating within the nozzle or pipe. The proximal end of the nozzle also features an inner lip, which facilitates the welding of the proximal end of the nozzle to an upper saddle member, which is used to clamp the nozzle to the pipe prior to cutting or pressure tapping of the pipe.