Duotight Flow Stopper - Automatic Keg Filler & Transfer Shut-Off

The Duotight Flow Stopper is the little device that ends one of kegging's most familiar moments: the keg that quietly filled while you stepped away, and the beer now running out of the gas post onto the floor. Attached to the gas post of the receiving keg, the Flow Stopper lets gas escape freely during filling — then the instant the keg is full, the rising liquid lifts the internal ball float against its stainless spring and seals the outlet automatically. Flow stops, nothing spills, and the transfer genuinely becomes set-and-forget: start it, walk away, and come back to a perfectly filled keg.

What makes the Flow Stopper especially valuable is where it fits in modern transfer practice. Closed, pressure-driven transfers — from a FermZilla, Kegmenter, or any pressurisable fermenter into a purged keg — are the standard route to oxygen-free packaging for hop-forward beers, and they all share the same problem: you can't see inside the receiving keg, so knowing when to stop is guesswork. The Flow Stopper removes the guesswork mechanically. Its clear acrylic sight glass body even shows you the float doing its job, so you can watch the shut-off happen. The same trick serves keg-to-keg transfers after fining or filtering, and ordinary keg filling of any kind — anywhere liquid goes into a keg and overfilling is the risk.

For the best results, pair the Flow Stopper with a BlowTie spunding valve connected to its outlet via a short length of 8mm OD EVABarrier tubing. The BlowTie holds head pressure on the receiving keg during the transfer, letting you control the flow speed and dramatically reduce foaming — particularly important when transferring carbonated beer. Built on standard Duotight 8mm push-fit fittings, the Flow Stopper drops straight into any existing Duotight and EVABarrier setup, tool-free and leak-free.

Duotight Flow Stopper — kit contents
2× Duotight 8mm × 5/8" push-in fittings, 1× ball float, 1× stainless spring, 2× straight 8mm joiners, 1× acrylic sight glass with 5/8" male thread on both sides. Supplied in parts — simple assembly required. Colours of the float and joiners may vary.

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Key Features

• Automatic shut-off — ball float and stainless spring seal the gas post the moment the keg is full
• Set-and-forget keg filling — no watching, no guesswork, no beer on the floor
• Clear acrylic sight glass — watch the float and the shut-off happen
• Ideal for closed pressure transfers from FermZilla, Kegmenter, and other pressurisable fermenters
• Duotight 8mm push-fit fittings — tool-free, leak-free, drops into any EVABarrier setup
• Pairs with a BlowTie spunding valve for pressure-controlled, low-foam transfers

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Usage

Best suited for: Automatic keg filling, closed fermenter-to-keg pressure transfers, keg-to-keg transfers after fining or filtering, oxygen-minimised packaging workflows

Compatible with: Ball lock keg gas posts, Duotight 8mm push-fit fittings, 8mm OD EVABarrier tubing, BlowTie spunding valve (recommended companion), FermZilla, Fermentasaurus, Kegmenter and other pressurisable fermenters

Note: Supplied in parts — assembly takes a couple of minutes and needs no tools. For carbonated transfers, use with a spunding valve on the outlet to hold head pressure and keep foaming down.

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Quick facts

Brand: KegLand (Duotight)
Type: Automatic keg filler / flow stopper
Mechanism: Ball float + stainless spring shut-off
Body: Acrylic sight glass, 5/8" male thread both sides
Fittings: Duotight 8mm push-fit (2× 8mm × 5/8", 2× straight joiners)
Connection point: Gas post of receiving keg
Use: Keg filling, closed transfers, keg-to-keg transfers, overflow prevention