Description
TL;DR: The B-FS4J is a G1/4 sealing stop plug paired with a barbed nipple sized for 13mm ID by 19mm OD soft tubing, designed to live at the lowest point of a custom liquid cooling loop as a dedicated drain port. In normal operation the cap stays threaded into a G1/4 port on a radiator, reservoir, or...
The B-FS4J is a G1/4 sealing stop plug paired with a barbed nipple sized for 13mm ID by 19mm OD soft tubing, designed to live at the lowest point of a custom liquid cooling loop as a dedicated drain port. In normal operation the cap stays threaded into a G1/4 port on a radiator, reservoir, or distribution plate and seals against an internal O-ring. When the loop needs to be drained, the cap is unscrewed and a short length of 13x19mm tube is slipped over the barb to direct coolant into a waste container. The fitting accepts the same G1/4 thread used by reservoirs, pumps, blocks, and rad ports, so no adapters are required.
Q: What tubing size does the B-FS4J accept?
A: 13mm inner diameter by 19mm outer diameter soft tubing. It will not seal correctly on 10x13 or 10x16 tube.
Q: What thread does it use?
A: Standard G1/4 male thread, compatible with any reservoir, radiator, pump top, block, or distribution plate that uses G1/4 ports.
Q: Is it watertight when plugged in?
A: Yes. The plug seals against an internal O-ring on the G1/4 thread, so the loop stays sealed until you unscrew it to drain.
Q: Where in the loop should it be installed?
A: At the lowest accessible G1/4 port in the loop, typically a bottom radiator port or the lowest point of a distro plate, so gravity drains the coolant when opened.
Q: Do I need to provide my own drain hose?
A: Yes. The B-FS4J is the plug and barb only. Cut a short piece of 13x19mm soft tube and slip it onto the barb when draining.