Choosing the right vent kit matters as much as choosing the heater itself. The wrong match can create installation headaches, poor performance, or compatibility problems.
This roundup focuses on horizontal tankless water heater vent kits that are practical, durable, and easier to match to common 2-inch and 3-inch setups.
Best 10 Horizontal Tankless Water Heater Vent Kits Picks for 2026
Compact Horizontal Termination Kit
DiversiTech HVENT2 2-Inch Vent Kit
- Low-profile horizontal termination design
- Includes all fittings for installation
- Works for horizontal or vertical setups
Best For: A clean, compact vent kit for high-efficiency appliances
Stainless Steel 3-Inch Vent Kit
CAMPLUX 3-Inch Horizontal Z-Vent Kit
- Detachable 3-inch vent components
- Adjustable wall thimble up to 7.8 inches
- Stainless steel and corrosion-resistant
Best For: Indoor gas tankless systems needing an adjustable horizontal vent kit
Concentric PVC Vent Kit
DiversiTech CVENT-3 3-Inch Concentric Kit
- Concentric design for intake and exhaust
- Includes all fittings for installation
- Works for horizontal or vertical termination
Best For: A clean-looking concentric vent for high-efficiency appliances
OEM Horizontal Cone Termination
Rheem ProTech RTG20291-1 Vent Kit
- OEM factory-authorized parts
- Snap-lock design for leak-free connection
- Rugged stainless steel construction
Best For: Rheem non-condensing units needing an OEM wall termination kit
Stainless Vent Pipe Set
Elbow And Termination Pipe Kit
- T304 stainless steel for rust resistance
- Includes elbow, termination pipe, and rain cap
- Works when vent diameter matches the heater
Best For: Gas tankless water heater owners needing a durable stainless vent kit
Rheem Wall-Termination Kit
3" x 5" Stainless Horizontal Vent Termination
- Stainless steel parts for durability and corrosion resistance
- Includes 12-inch wall plate, screws, and 94-degree elbow
- Adjustable to fit wall thicknesses up to 10 inches
Best For: Rheem EcoSense indoor direct vent tankless gas heaters
GASLAND Modular Vent Kit
3" Stainless Horizontal Vent Pipe Kit
- T304 stainless steel for corrosion and temperature resistance
- Detachable sections allow custom assembly length
- Includes hood, elbow, pipe sections, wall thimble, and clamps
Best For: Custom-fit 3-inch venting for compatible GASLAND heaters
Compact Horizontal Termination Kit – DiversiTech HVENT2 2-Inch Vent Kit
If you need horizontal tankless water heater vent kits that keep the outside finish clean and simple, the DiversiTech HVENT2 is built around a low-profile horizontal termination design. It is made for venting high-efficiency fossil fuel appliances and includes all fittings for a hassle-free install, with the added flexibility to work for both through-the-wall and through-the-roof setups.
Best For: Buyers who want a compact, low-profile vent termination kit for tankless water heaters and other high-efficiency appliances.
Pros:
- Low-profile horizontal design helps conceal intake and exhaust pipework
- Includes all fittings needed for installation
- Designed for proper venting of high-efficiency fossil fuel appliances
- Can suit both horizontal and vertical installations
Cons:
- Product details do not specify exact appliance compatibility beyond high-efficiency appliances
- 2-inch sizing may not fit systems that use larger venting
Overall, this is a practical pick if you want a straightforward termination kit that focuses on clean appearance and complete hardware. Its flexible install options make it a useful fit when the vent path needs to stay tidy and efficient.
Stainless Steel 3-Inch Vent Kit – CAMPLUX 3-Inch Horizontal Z-Vent Kit
For shoppers comparing horizontal tankless water heater vent kits, this CAMPLUX 3-inch stainless steel set is aimed at indoor gas tankless systems that need a detachable, configurable vent path. It includes the core parts for a quick installation, a low-resistance vent pipe design, and an adjustable wall thimble that stretches to fit thicker walls.
Best For: Indoor gas tankless water heater owners who need a 3-inch horizontal vent kit with adjustable wall fit.
Pros:
- Detachable design can be assembled in lengths to suit your setup
- Includes termination hood, wall thimble, elbow, and vent pipe components
- Adjustable wall thimble fits walls up to 7.8 inches thick
- Stainless steel construction is corrosion-resistant and easy to clean
Cons:
- Designed for 3-inch venting, so it is not universal
- Primarily described for indoor gas tankless water heaters
This is a strong choice if you want a kit that arrives with the key pieces already included and can adapt to your wall depth. Its low-resistance, rustproof build makes it especially appealing for a tidy, serviceable install.
Concentric PVC Vent Kit – DiversiTech CVENT-3 3-Inch Concentric Kit
If your priority is a tidy installation, this DiversiTech CVENT-3 stands out among horizontal tankless water heater vent kits because it uses a concentric design to help conceal both intake and exhaust pipework. The kit is built for high-efficiency furnaces and tankless gas water heaters, and it includes the fittings needed for horizontal or vertical termination.
Best For: Buyers who want a concentric vent solution with a clean exterior look for high-efficiency appliances.
Pros:
- Concentric dual-pipe design helps streamline installation
- Conceals intake and exhaust pipework for a cleaner appearance
- Includes all fittings needed for installation
- Suitable for both horizontal and vertical termination
Cons:
- PVC construction may not suit buyers who want metal vent parts
- 3-inch system sizing may not match every appliance
This kit makes sense when appearance and a simplified exterior termination matter as much as functionality. It is a practical option for installations that call for a concentric PVC vent with a complete parts package.
OEM Horizontal Cone Termination – Rheem ProTech RTG20291-1 Vent Kit
Among horizontal tankless water heater vent kits, this Rheem ProTech cone termination kit is a straightforward OEM option for compatible non-condensing water heaters. It features rugged stainless steel construction, an exclusive snap-lock design for leak-free connection, and hardware and instructions when applicable to support installation.
Best For: Rheem owners who want a genuine factory-authorized horizontal vent termination kit for a non-condensing unit.
Pros:
- Genuine factory-authorized OEM parts
- Rugged stainless steel construction for durability
- Exclusive snap-lock design for leak-free connection
- Includes hardware and instructions when applicable
Cons:
- Built for tankless non-condensing water heaters, so compatibility is narrower
- Wall dimensions are specific to 2 in. x 6 in. walls
This is the most brand-specific option in the group, which is useful if you want OEM fit and finish for a Rheem setup. Its durable metal build and leak-resistant connection design make it a dependable replacement or install part when compatibility matches.
3-Inch Stainless Kit – Compact 3" Vent Kit With Elbow
If you’re shopping for horizontal tankless water heater vent kits, this stainless steel option is a straightforward fit for systems that specifically use 3-inch venting. It includes a 24.1-inch pipe section, a 3-inch elbow, aluminum tape, and a silicone pad, making it a practical choice when you want a compact setup with corrosion-resistant materials.
Best For: Buyers who need a 3-inch stainless vent kit for a compatible tankless water heater and want a simple, space-saving install.
Pros:
- Made from stainless steel for corrosion resistance and long-term durability
- Includes a 3-inch elbow plus aluminum tape and silicone pad
- Compact 24.1-inch length supports flexible installation
- Designed for straightforward setup in residential or commercial settings
Cons:
- Only works with 3-inch diameter venting
- Not suitable if you need 2-inch, 4-inch, 5-inch, or other sizes
- Compatibility depends on your specific tankless water heater model and vent size
This is a solid pick if you already know you need a 3-inch horizontal vent solution and want a durable, low-profile kit. The main thing to verify before buying is diameter, since the product is explicitly limited to 3-inch systems.
Low-Profile Termination – 2" Horizontal Vent Kit
Among horizontal tankless water heater vent kits, this SP20285 termination kit is aimed at low-profile outside-wall venting for 2-inch PVC or ABS pipe. It’s designed to cover both intake and exhaust pipework and comes with screws, which makes it a practical option when you want a cleaner exterior finish without extra fittings.
Best For: Homeowners needing a 2-inch horizontal vent termination kit for a tankless gas water heater or other high-efficiency appliance.
Pros:
- Designed for 2-inch PVC and ABS pipes
- Low-profile look helps conceal intake and exhaust pipework
- Includes screws for a more complete install
- Suitable for horizontal through-wall or vertical through-roof use
Cons:
- Only suitable for 2-inch pipe sizes
- Requires careful measurement before installation
- Centered spacing is fixed at 4 inches
If your setup calls for a 2-inch horizontal termination and you care about exterior appearance, this kit is a sensible match. Just confirm pipe size and cut dimensions first, since the product is very specific about fit.
Stainless Vent Pipe Set – Elbow And Termination Pipe Kit
If you want horizontal tankless water heater vent kits built around stainless steel, this FOGATTI set gives you the essential pieces for a basic exhaust run. It includes an elbow, a horizontal termination pipe, and a chimney rain cap, and it is made from T304 stainless steel for corrosion resistance and high-temperature tolerance.
Best For: Buyers who want a durable stainless vent pipe kit with the core parts needed for a compatible gas tankless water heater.
Pros:
- T304 stainless steel construction for durability and rust resistance
- Includes elbow, horizontal termination pipe, and chimney rain cap
- Simple assembly with straightforward installation steps
- Compatible with gas tankless water heaters when diameter matches
Cons:
- Diameter must match your required vent size
- Limited to the included components for the kit configuration
- Compatibility still depends on the specific heater setup
This kit makes sense if you want a stainless, no-frills venting package with the key pieces already included. It’s best suited for buyers who know their required diameter and want a durable option for horizontal venting.
Rheem Wall-Termination Kit – 3" x 5" Stainless Horizontal Vent Termination
If you need horizontal tankless water heater vent kits for a Rheem non-condensing gas unit, this ProTech termination kit is built for through-the-wall installations. It uses stainless steel components, includes the wall plate and hardware, and is sized for 3" x 5" venting with a 94-degree elbow to help complete the vent path.
Best For: Rheem EcoSense mid-efficiency indoor direct vent tankless gas heaters with through-the-wall venting needs.
Pros:
- Stainless steel construction for durability and corrosion resistance
- Includes a 12-inch wall plate with mounting screws
- 94-degree elbow supports proper vent configuration
- Adjustable for wall thicknesses up to 10 inches
Cons:
- Designed specifically for Rheem EcoSense mid-efficiency units
- Only suited to 3" x 5" horizontal vent setups
- May be more than you need if you do not require a complete termination assembly
Overall, this is a solid pick when you want a purpose-built termination kit with the main installation parts included. The key advantage is the adjustable wall thickness range, which adds flexibility during install.
GASLAND Modular Vent Kit – 3" Stainless Horizontal Vent Pipe Kit
Among horizontal tankless water heater vent kits, this GASLAND option is a practical modular setup for 3-inch exhaust ports. It combines a termination hood, elbow, vent pipe sections, and a wall thimble, so you can assemble the length you need for a residential tankless installation.
Best For: Buyers wanting a configurable 3-inch stainless steel vent kit for compatible GASLAND or other gas tankless heaters.
Pros:
- T304 stainless steel construction for corrosion and heat resistance
- Detachable design lets you assemble to the length you need
- Includes termination hood, elbow, vent pipes, wall thimble, and gear clamps
- Broad compatibility with many GASLAND tankless models
Cons:
- Requires a gas tankless water heater with a 3-inch exhaust port
- Compatibility is focused on specific model families
- May require matching with other GASLAND venting components for best performance
This kit makes sense if you want a flexible venting solution with the main components in one box. Its modular layout is the standout feature, especially for installs that need custom assembly.
Thermomate Universal Vent Kit – 3" Universal Stainless Horizontal Vent Kit
If you are comparing horizontal tankless water heater vent kits for a standard 3-inch gas unit, this Thermomate universal kit is built to cover replacements or new installs. It includes the key vent parts for an indoor horizontal run and uses T304 stainless steel for better corrosion resistance and high-temperature tolerance.
Best For: Homeowners and installers needing a universal 3-inch vent kit for most gas tankless water heaters.
Pros:
- Universal fit for most standard 3-inch gas water heaters
- T304 stainless steel resists rust, corrosion, and heat
- Detachable design supports custom assembly lengths
- Includes termination hood, elbow, vent pipes, and wall thimble
Cons:
- Still limited to systems that use a 3-inch diameter exhaust port
- Universal compatibility may not cover every niche model
- Basic kit format may require additional planning for unique installs
For a straightforward 3-inch horizontal venting project, this kit offers a clean mix of universal compatibility and durable materials. It is a sensible option when you want flexibility without buying a brand-specific assembly.
How We Picked the Best Horizontal Tankless Water Heater Vent Kits
We prioritized compatibility, vent diameter options, material quality, and whether each kit supports a straightforward horizontal termination. We also looked for clear use cases, since some kits are made for condensing units while others are intended for non-condensing tankless models.
Quick Comparison
Most buyers will narrow the field by three things: vent size, heater type, and wall configuration. In this group, 2-inch kits are typically the better fit for some compact systems, while 3-inch stainless steel kits are common for broader compatibility and longer-term corrosion resistance.
Key Buying Factors for Horizontal Tankless Water Heater Vent Kits
1. Match the Heater Type
Always confirm whether your unit is condensing or non-condensing. The venting requirements are different, and using the wrong kit can void warranties or create unsafe operation.
2. Check Diameter and Clearance
Measure the required vent size exactly. A 2-inch kit will not replace a 3-inch setup, and wall thickness, elbow orientation, and termination clearances all affect fit.
3. Choose the Right Material
Stainless steel is the safest all-around choice for many buyers because it resists heat and corrosion well. Lower-cost kits can still work, but they should be matched carefully to the manufacturer’s specifications.
4. Confirm What Is Included
Some Horizontal Tankless Water Heater Vent Kits include only the termination piece, while others add elbows, pipe sections, wall thimbles, or rain caps. Make sure you are not missing a required part before installation day.
5. Follow Local Code and Manufacturer Instructions
Venting is not a place to guess. Local building code, clearances from openings, and permitted termination locations all matter. When in doubt, have a licensed installer verify the layout.
Who Should Buy Which Horizontal Tankless Water Heater Vent Kits?
If you want the safest all-around pick, choose a stainless steel 3-inch kit with a complete accessory list. If your water heater specifically calls for a 2-inch termination, stick to the exact size rather than “upgrading” to a larger vent. Homeowners replacing an older unit should double-check brand compatibility, especially with Rheem, Camplux, Fogatti, Gasland, or Thermomate systems, because fit and venting standards can vary by model.
In short, the best option is the one that matches your heater, your wall setup, and your code requirements—not just the one with the most parts.
