NATGAI 6 x 6 x 4 Inch 3 Way Duct Splitter, 45°Metal Hose Connector 6 Inch Duct Connector, Y-Shaped Ducting Adapter for HVAC, Dryer Vent, Exhaust Fan, Ventilation Systems in Kitchen & Bathroom

Why I reached for this Y‑splitter

Splitting a single run of duct into multiple branches is one of those tasks that looks simple on paper but can punish you with noise, leaks, and frustrating balancing issues if the fitting isn’t right. I put the NATGAI 6x6x4 Y‑splitter to work on a crawlspace project where I needed to divert a 6-inch line and peel off a 4-inch branch to a smaller zone. After a few weeks of use, I have a clear sense of where this fitting shines and where you’ll want to plan ahead.

Build and design

This is a galvanized steel Y at a true 45 degrees, with two 6-inch ports and one 4-inch port. Out of the box, it feels more substantial than many off-the-shelf wyes I’ve used. The gauge isn’t listed, but the rigidity was obvious: no oil-canning when I pressed on the body, and the necks didn’t deform during clamp-up. The finish is the usual silver galvanizing—clean and uniform—with tidy seams.

Two details matter in the field and both are executed well here:
- The interior is notably smooth. The longitudinal seam is tight and doesn’t protrude into the airflow path, which helps keep static pressure and turbulence in check.
- The ends are lightly beaded/rolled. That soft edge is more than a nicety; it reduces the chance of cutting flex duct or your hands during installation and gives hose clamps a better bite.

There are no integral dampers or takeoff collars—this is a straightforward wye. The ends are round and true to size, so 6-inch and 4-inch flex and pipe mated without persuasion.

Installation experience

I installed the Y‑splitter in a cramped crawlspace, tying into a 6-inch insulated flex trunk and stepping off with a 4-inch branch to a small enclosure. It was an easy install, but a few notes can save you time:

• Orientation: If you need a gentle split, the 45-degree geometry is your friend. Keep the primary 6-inch path as straight as possible and use the 4-inch as the side branch to reduce mixing losses.
• Connections: The ports accepted standard flex cuffs and smooth 30-gauge snap-lock pipe without gapping. I used three short sheet-metal screws per joint to secure, followed by UL 181 foil tape. If this is a permanent installation, mastic over the tape is even better.
• Clamps: Since clamps aren’t included, bring worm-drive clamps sized for insulated flex. The beaded edges help clamps sit flat and promote a good seal.
• Support: Even though the fitting is light enough to handle solo, it’s still metal—strap it. I used 1-inch hanger strap to offload weight from the flex and keep the wye from sagging at the joints.
• Sealing the seams: The factory seam is tight, but I still ran a thin bead of mastic over it as a best practice. After a smoke test, I saw no visible leakage.

Total install time, including strapping and sealing, was under an hour, largely because the roundness and rolled edges kept the connections pain-free.

Airflow and performance

Performance in a splitter like this boils down to three things: pressure drop, leakage, and how predictable the split is.

• Pressure drop: A 45-degree Y will almost always beat a hard tee for pressure loss, and that was the case here. The main 6-inch path behaved like a mild offset rather than a hard elbow. System static went up only slightly once the 4-inch branch was opened.
• Leakage: With screws and tape, plus a light coat of mastic, leakage was negligible on a blower door–style spot check. The smooth interior seam does its part, but don’t skip sealing; even tiny gaps add up.
• Distribution: Don’t expect equal flows out of the box. A 6-inch main coupled with a 4-inch side branch will inherently favor the 6-inch path. If you need to apportion air precisely, add balancing dampers downstream. Once I throttled the main slightly, the 4-inch run received the target CFM without a noise penalty.

Noise was a non-issue. No whistling at the 4-inch neck, and only a small uptick in air noise when I pushed the system at higher static. The 45-degree geometry helps keep turbulence down.

Where it fits and where it doesn’t

This fitting is at its best in residential and light commercial ventilation where you’re splitting a 6-inch run to serve a secondary, smaller load:
- Bathroom and utility fans stepping off a 6-inch trunk to a 4-inch branch
- Fresh air or supply distribution in small zones
- Dehumidifier or HRV/ERV distribution where you want a gentle side takeoff
- Garage or workshop exhaust where a smaller branch serves a localized pickup

Two cautions:
- Dryer vents: Many jurisdictions and manufacturers require a dedicated, single-run duct for clothes dryers. A wye that ties a dryer into other branches is typically not allowed. If you’re using this for a dryer, keep it as a dedicated transition or service fitting, not a shared line.
- Grease and commercial kitchen use: For grease-laden vapors, specialized ducting and listed fittings are required. This general-purpose galvanized wye isn’t meant for that.

Outdoors, the galvanization will resist rust, but any cut edges and seams are still potential corrosion points. If you’re exposing it to the elements, seal the seams well and consider a protective coating.

Durability and build quality over time

After installation, I went back a couple of weeks later in a humid crawlspace to check fasteners and seals. No creep at the joints, no galling from clamps, and no surface rust. The heavier feel of the steel translates into less flex and better thread engagement on screws. If you’ve ever had a thin-walled wye collapse slightly under a clamp and create an oval that fights your duct, you’ll appreciate the stiffness here.

Practical tips for best results

• Use balancing dampers or butterfly valves downstream if you care about precise CFM splits.
• Seal everything: three screws per joint, UL 181 foil tape, then mastic. It’s extra minutes that save energy and reduce dust draw.
• Support each branch within 4–5 feet of the fitting to keep weight off the necks.
• If you’re transitioning from rigid to flex, keep at least the first couple of feet rigid after the wye on the high-flow path to reduce noise and preserve airflow.
• Label branches while you’re there; future you will thank you.

Limitations

A few things to know before you buy:
- No integral dampers, so airflow balancing requires separate parts.
- The 4-inch branch is appropriately sized for small exhausts, but if you’re feeding a longer run or higher CFM device, it may become the system bottleneck—plan for static.
- It’s not insulated. If you’re in an unconditioned space carrying conditioned air, wrap it to prevent condensation.
- The 45-degree angle is fixed. If your layout needs a sharper takeoff or a lateral wye, you may need an additional elbow.

None of these are deal-breakers, but they’re worth considering in your design.

The bottom line

The NATGAI 6x6x4 Y‑splitter does the simple things right: solid galvanized construction, smooth interior, true sizing, and rolled edges that make installation safer and easier. In my project it installed cleanly, sealed up without drama, and delivered predictable, low-turbulence splits once I added balancing. It’s a straightforward, durable fitting that behaves like a wye should.

Recommendation: I recommend this Y‑splitter for residential and light commercial ventilation work where you need to split a 6-inch line and peel off a 4-inch branch, and you value sturdier steel and cleaner seams than the bargain-bin alternatives. Pair it with proper clamps, UL 181 tape or mastic, and downstream dampers for best results. I would not recommend it for shared dryer venting or grease applications due to code and safety considerations, but within its intended use, it’s a reliable, well-made piece of hardware that makes for an easy, leak-free install.