AN Fitting vs NPT Fitting: Which Should You Use?

Quick answer

Use AN flare fittings for every connection you'll take apart more than once, and reserve NPT for ports machined into a pump, regulator, or tank that won't be opened repeatedly. AN seals on a 37-degree flare with no thread sealant, so it survives reassembly; NPT seals on tapered threads and needs sealant, so each re-tightening risks distortion and leaks. If your component only offers NPT, adapt once with a proper adapter and run AN from there.

Most fuel system leaks trace back to one decision made early: which thread style you built around. AN and NPT look similar at a glance, both are metal-to-metal joints, and both hold pressure when done right, but they seal in completely different ways. That difference decides how often you can service a joint, whether you need sealant, and how much torque the parts will tolerate.

This comparison covers how each fitting type actually seals, where each belongs in a fuel system, and the trade-offs you accept when you mix them. It also walks through real DeatschWerks parts so you can see how the choice plays out in a feed line, a filter, and a pump module.

How AN and NPT fittings seal differently

An AN fitting is a flare joint. A 37-degree male flare seats against a matching female flare, and the seal happens at that angled face. Threads only provide clamping force, they never touch the fluid path, which is why AN joints go together dry and come apart cleanly. The trade-off is that both halves must be machined to the same flare angle and the flare must be undamaged; a nick or a piece of debris on the seat will weep under pressure.

An NPT fitting is a tapered thread joint. The threads themselves are the seal, and they deform slightly as you tighten. That interference is what stops the leak, so NPT needs a sealant, tape or paste, and it needs to be tight enough to engage the taper without cracking the port. The trade-off is serviceability: every re-tightening wears the threads a little more, and after a few cycles the joint may never seal the same way again.

• AN: dry assembly, reusable, torque is predictable, requires matching flare angles.
• NPT: sealant required, low reusability, torque depends on thread engagement, not a spec value.

Where each fitting type belongs in a fuel system

AN belongs anywhere you expect to open the system: pump outlets, filter bodies, rail inlets, regulator ports, and any line you might reroute. Because the seal is at the flare, you can loosen and retighten an AN joint many times without degrading it, which matters on a car that gets tuned, logged, or modified over several seasons. AN also gives you a standardized size language, so a -8AN feed is a -8AN feed regardless of who made the hose end.

NPT belongs at fixed ports that were designed that way at the factory, typically on pumps, tanks, and some regulator bodies. You install the NPT side once, seal it, and leave it alone. The mistake is treating NPT as a general-purpose connection and building a whole line from it; that turns every future service into a thread-sealing job and multiplies leak points.

• Count how many times you'll open each joint before choosing the thread.
• Keep NPT confined to the component port, then convert to AN immediately.

Adapting between AN and NPT without creating a leak

The clean way to cross between the two is a single adapter that is AN on one end and NPT on the other. The NPT side gets sealant and goes in once; the AN side stays dry and serviceable forever after. DeatschWerks sells exactly this kind of part, the 8AN to M12 X 1.5 Metric Adapter, which is an 8AN male flare to M12 X 1.5 male metric adapter including a crush washer, finished in anodized DW Titanium. That crush washer is the sealing element on the metric side, so it is a one-time-use item, not something to reuse.

The trade-off with adapters is stack height and one more joint. Every adapter adds a connection that can loosen and a small amount of extra length in the line, which matters in tight engine bays. The benefit is that you stop fighting tapered threads on parts you actually service. If you're already running a metric port, adapt once and keep the rest of the system AN.

• Apply sealant to the NPT or metric side only, never to the AN flare.
• Replace crush washers and sealing washers when you disturb the joint.

Matching hose and filter hardware to your thread choice

Once you commit to AN, the hose and filter ends need to match. The 20 ft, 10AN SS Double Braided CPE Hose is a 10AN stainless steel double braided CPE hose sold in a 20-foot length, which suits a full feed line run. CPE is the more flexible, more forgiving choice for a street car where the line has to bend around factory routing. If you need a shorter piece for a specific jump, the 3 ft, 10AN SS Double Braided PTFE Hose is the same 10AN stainless double braided construction in PTFE, sold in a 3-foot length; PTFE is the pick when the fluid or the environment demands a more chemically inert liner.

On the filtration side, the 3/8 in, 100 micron, 70mm In-line fuel filter kit is an in-line filter element and housing kit with a stainless steel 100 micron element, 3/8-inch hose barb, and 70mm body, universal fit. Note the barb: that is not an AN connection, so plan your adapters before you cut hose. If you already run a DW 110mm housing, the 100 micron, 110mm, In-line fuel filter element is the stainless 100 micron replacement element for it, universal fit. The trade-off is that these are 100 micron elements, which protect the pump and catch debris but are not a fine post-pump filter.

• Decide AN or barb at the filter before you order hose and ends.
• Buy hose in the length your routing needs, not the length that's on sale.

When a complete plumbing kit beats mixing parts

If your car is a known application, a pre-assembled plumbing kit removes most of the thread guesswork. The X2 Series Pump Module PTFE Plumbing Kit for 2010-15 Camaro Base or SS is built as an X2 Series pump module plumbing kit with -8AN feed and -6AN return in PTFE, for 2010-15 Camaro Base or SS with the 3.7 V6 or 6.2 LS3. Because the feed and return sizes are already set and the hose is PTFE, you're not choosing between AN and NPT at every junction, the kit has made those decisions for the application.

The trade-off is specificity. A kit like this only fits the listed applications and engine codes, and it locks you into its feed and return sizing. If your build is outside that list, or you plan to change the fuel system later, buying individual AN hose and ends gives you more freedom at the cost of more measuring and more chances to order the wrong piece.

• Confirm your exact year, trim, and engine code before ordering an application-specific kit.
• If you're unsure of your port threads, measure or verify before buying adapters.

AN vs NPT trade-offs at a glance

• Sealing method: AN seals on a 37-degree flare face and needs no sealant; NPT seals on tapered threads and requires tape or paste. If you can't keep sealant out of the fluid path, choose AN.
• Reusability: AN joints can be opened and retightened repeatedly; each NPT re-tightening wears the tapered threads. Count your expected service cycles before committing to NPT.
• Where it belongs: AN for serviceable lines and components; NPT for fixed factory ports you install once. Adapt NPT to AN at the port and keep the rest of the system AN.
• Kit convenience vs flexibility: Application-specific kits like the X2 Series Camaro kit set feed and return sizing for you; individual hose and ends let you build outside that list. Verify year, trim, and engine code before choosing a kit over parts.

DeatschWerks parts that show the difference

• 8AN to M12 X 1.5 Metric Adapter: 8AN Male Flare to M12 X 1.5 Male Metric Adapter (Incl Crush Washer), Anodized DW Titanium A single adapter is the correct way to leave a metric or NPT port once and run serviceable AN from that point on.
• 20 ft, 10AN SS Double Braided CPE Hose: 10AN Stainless Steel Double Braided CPE Hose, 20 Feet A full-length 10AN feed line in CPE, the more flexible option for street routing where the hose has to bend.
• 3 ft, 10AN SS Double Braided PTFE Hose: 10AN Stainless Steel Double Braided PTFE Hose, 3 Feet Same 10AN stainless double braided construction in PTFE for short runs where a more inert liner is the priority.
• 3/8 in, 100 micron, 70mm In-line fuel filter kit: In-line fuel filter element and housing kit, stainless steel 100 micron, 3/8in hose barb, 70mm. Universal The 3/8-inch hose barb means this filter is not an AN connection, so plan adapters before cutting hose.

Which should you use?

Choose AN if

• You plan to open, reroute, or upgrade the fuel system more than once
• You want dry assembly with no sealant in the fluid path
• Your components already offer AN ports or you can adapt to them once

Choose NPT if

• You expect to disassemble and reassemble the joint often
• You want a standardized, reusable connection across brands
• You're building a full line rather than sealing a single fixed port

Pick AN for anything you'll service and NPT only where the component forces it, then adapt once and stay AN from there. Match your hose, filter ends, and adapters to that decision before you cut anything, and the system will come apart and go back together without a new leak each time.