Navigating fittings is one of the most technical parts of building a brewery or winery. This guide breaks down the most common thread types and standards used.
CRITICAL: Understanding "Trade Sizes"
Before identifying your threads, it is important to note that listed sizes (like 1/2" or 3/4") do not refer to the actual diameter of the threads. Instead, these are "Trade Sizes" based on the approximate Internal Diameter (ID) of the pipe the fitting is designed for.
For example, a 1/2" NPT male fitting actually measures approximately 0.84 inches in outer diameter. If you take a ruler to your threads and they measure 1/2", you are likely looking at a 1/4" trade size fitting. Always consult a thread pitch chart if you are measuring with calipers.
1. NPT (MPT/FPT) & Iron Pipe (MIP/FIP)
While often used interchangeably, there is a technical distinction in how they seal.
NPT (National Pipe Thread): These are Tapered threads. The diameter gets smaller toward the end, creating a wedge seal as you tighten.
IP (Iron Pipe / NPS): These are typically Parallel (straight) threads.
Compatibility: NPT (tapered) and NPS (parallel) have the same thread pitch. They are compatible and will thread together, but for high-pressure brewing applications, it is best to use the same type for a perfect fit.
Sealing: Both require Teflon tape or pipe dope to lubricate the threads and fill the gaps to prevent leaks.
2. BSP, BSPP, and BSPT (British Standard Pipe)
Commonly found on European manufacturers like Speidel, KegLand, Marchisio, and Brewtools.
BSP / BSPP: If a product is labeled "BSP" without a suffix, it almost always refers to BSPP (Parallel). In technical drawings, this is also called G-Thread.
BSPT: This is the Tapered version. It is rare in homebrewing but common in industrial plumbing.
Sealing: Because BSPP is parallel, they ideally require a gasket, O-ring, or bonded seal to sit between the male and female faces. You can also use thread tape to seal however you may need a few more wraps than the typical 3 to 4.
Warning: NPT and BSP look similar but have different thread angles. Do not force them together or you will strip the threads.
1/2" NPT and BSP: While NPT and BSP are mostly non compatible, 1/2" BSP and NPT can be combined with thread tape to seal.
3. MFL & FFL (Flare Fittings)
Flare fittings are the industry standard for homebrew gas and liquid lines.
Metal-on-Metal Sealing: When connecting two stainless or brass flare fittings together (e.g., a stainless swivel nut to a brass regulator nipple), you must use a Flare Gasket (a small plastic washer). Without this, the metal-on-metal connection will almost always slow-leak CO2.
- 1/4" Standard: Most flare options in the brewing world (like those on CO2 regulators or manifold outlets) are 1/4" MFL. Note that while they are called 1/4", the actual thread measurement is technically SAE 7/16"-20.
Ball Lock Disconnects: Most Ball Lock or Pin Lock QDs feature built-in flare washers tips on the male threads. These do not require an additional flare gasket to seal against the swivel nut.
4. Compression Fittings
Compression fittings allow for sanitary connections.
Metal Compression: Uses a nut and a metal ring (ferrule) that "bites" into stainless or copper tubing. These are permanent once tightened.
Soft/Rigid Hose Compression: Used with plastic tubing (like EVABarrier). These use a "push-in" collet or a nut that compresses the hose over an internal barb.
Under-Sink Sizes (US): Most US kitchen faucets use a 3/8" Compression male thread. To adapt a brewery hose to a sink, you typically need a 3/8" Female Comp x 1/2" NPT or GHT adapter.
5. GHT (Garden Hose Thread)
The standard thread for outdoor faucets and immersion chillers.
Specs: GHT is a wide, coarse parallel thread.
Sealing: It relies entirely on a thick rubber hose washer compressed against the flat face of the fitting. Teflon tape is ineffective here.
Note: GHT is not compatible with 3/4" NPT, despite looking deceptively similar in size, see our Brass GHT to NPT adapter options..