The best choice depends on whether you need a side-wall vent system, a vent-pipe kit, an outdoor installation accessory, or a replacement power-vent blower. The Tjernlund VP-3F is suited to certain millivolt gas water heaters, while the Rheem blower assembly is a replacement part for residential power-vent units. The other options are venting accessories, not complete water heaters. Confirm appliance compatibility, vent diameter, and installation requirements before buying.
| Product | Best For | What It Is |
|---|---|---|
| Tjernlund VP-3F | Millivolt gas water heaters | Side-wall vent system |
| ThermoMate 3-inch Vent Pipe Kit | Installations needing a 3-inch horizontal vent kit | Vent components |
| Rheem RTGH-X Outdoor Vent Kit | Compatible Rheem RTGH-3 models installed outdoors | Outdoor vent accessory |
| Rheem SP21031A Blower Assembly | Repairing a compatible Rheem residential power vent | Replacement blower assembly |
| SP20285 Horizontal Vent Termination Kit | Projects using 2-inch PVC or ABS vent pipe | Vent termination kit |
Tjernlund VP-3F Side Wall Vent System
Best for: Owners of qualifying millivolt gas water heaters who need a side-wall venting arrangement. The listed product information says it vents any brand or type of millivolt gas water heater in the stated capacity range of 60,000 to 120,000 BTU.
The system may allow the heater to be located up to 75 feet from an outside wall. Its listing also says no electrician is needed. Those details make it a useful candidate when the appliance location and vent route are important constraints.
Why it was selected: It is the clearest option in this list described as a side-wall vent system for water heaters, rather than a pipe kit or replacement component.
Limitation: The stated application is millivolt gas water heaters in a specific BTU range. Do not assume it suits a different control type or appliance without checking the manufacturer’s requirements.
ThermoMate 3-Inch Vent Pipe Kit
Best for: Buyers whose installation calls for the listed 3-inch horizontal vent components and whose appliance documentation permits this kit. It is described for most standard 3-inch gas tankless water heaters, including ThermoMate and other major brands.
The package includes a 3-inch termination hood, a 90-degree elbow, one 1-foot vent pipe, one 1.5-foot vent pipe, and a wall thimble. The listed purpose is to discharge combustion exhaust from residential tankless water heaters.
Why it was selected: The kit bundles several named parts, which can be convenient when a project needs a termination hood, elbow, short pipe sections, and wall thimble together.
Limitation: “Most” does not mean every appliance. Confirm the required vent material, diameter, layout, and approved components for the specific water heater before installation.
Rheem RTGH-X Outdoor Vent Kit
Best for: Owners planning an outdoor installation of a compatible Rheem high-efficiency tankless water heater. The product information specifies Rheem RTGH-3 models.
An outdoor setup may save indoor space and reduce venting costs, according to the listing. Assembly is described as requiring a Phillips-head screwdriver. These are practical considerations for buyers deciding between an indoor vent route and an outdoor appliance location.
Why it was selected: It addresses a different installation need from conventional vent pipe kits: adapting a specified Rheem tankless model for outdoor installation.
Limitation: Compatibility is specifically identified for RTGH-3 models. Do not treat this kit as a universal accessory for other Rheem heaters or other brands.
Rheem SP21031A Power-Vent Blower Assembly
Best for: A homeowner or service professional replacing or repairing an existing Rheem residential power-vent blower assembly, after confirming the part number matches the appliance.
The listing describes the SP21031A as an OEM genuine factory-authorized part for use in residential power vents. It is identified as a replacement or repair component, not as a complete water heater or a full venting system.
Why it was selected: A working blower is central to a power-vent system’s operation, and this is the only product in the list specifically identified as a residential power-vent blower assembly.
Limitation: The supplied details do not identify compatible water-heater models. Verify the original part number and appliance documentation before ordering.
SP20285 2-Inch Vent Termination Kit
Best for: Installations that specifically use 2-inch PVC or ABS pipe and need a low-profile termination for an outside wall. The listed center-to-center measurement is 4 inches.
The kit is described for venting high-efficiency fossil-fuel appliances, including tankless water heaters and furnaces. Its low-profile design conceals intake and exhaust pipework. The product information also describes horizontal through-wall and vertical through-roof use.
Why it was selected: It offers a defined 2-inch termination option for buyers who need to finish a vent opening and prefer a less exposed exterior appearance.
Limitation: The listing says it is suitable only for 2-inch PVC and ABS pipes. Confirm both pipe material and diameter; a different vent size is not an equivalent fit.
Buying Guide: How to Choose a Power-Vent Option
Are you buying a water heater or a vent component?
These five products are accessories or replacement parts, not complete gas water heaters. The Tjernlund product is a side-wall vent system; the ThermoMate and SP20285 products are venting components; the Rheem RTGH-X is an outdoor vent kit; and the SP21031A is a blower assembly. Start by identifying the actual project: a new appliance installation, a vent-route change, an outdoor installation, or a repair.
If you need a complete water heater, compare full appliance models separately. A vent kit or blower cannot replace the heater itself. Likewise, a vent termination does not necessarily include every component required for an approved installation.
Which appliance and fuel system does the part support?
Use the water heater’s model and installation manual to identify approved venting parts. The Tjernlund VP-3F listing specifies millivolt gas water heaters and a 60,000-to-120,000-BTU range. The Rheem outdoor kit identifies RTGH-3 models. The Rheem blower listing does not name compatible models, so its part number must be checked against the appliance.
Do not infer compatibility from a shared brand name, a similar-looking part, or a broad phrase such as “most gas tankless water heaters.” The exact model, vent system, and manufacturer instructions matter.
What vent diameter and material are required?
Diameter and material are essential checks. The SP20285 kit is specified for 2-inch PVC and ABS pipe. The ThermoMate kit is described as a 3-inch system and includes matching 3-inch components. These products are not interchangeable just because both are intended for horizontal venting.
Check the water heater’s instructions for approved vent material, diameter, maximum layout, and termination details. Do not choose pipe solely by measuring the opening or matching a component that is already installed; an existing setup may not follow the current appliance requirements.
Is the installation through a wall, through a roof, or outdoors?
Choose a component designed for the intended route. The Tjernlund system is described for side-wall venting and allows a heater location up to 75 feet from an outside wall, subject to the product’s application limits. The SP20285 listing describes horizontal and vertical installation. The ThermoMate kit includes a termination hood, elbow, pipe sections, and wall thimble for a horizontal vent arrangement.
The Rheem RTGH-X serves a different purpose: it is an outdoor vent kit for compatible tankless models. Before deciding on an outdoor or indoor location, confirm the appliance’s installation instructions and local requirements.
Do you need a blower replacement or a complete vent route?
A blower assembly is a repair part, not a complete vent system. Choose the Rheem SP21031A only when the task is replacing or repairing a matching residential power-vent blower. Confirm the existing part number and appliance model first.
For a new vent route, look at the system or termination components instead. A pipe kit may contain several pieces but still may not cover every requirement of a particular installation. Compare the included parts with the appliance manual and the planned route before purchasing.
What should you verify before ordering?
- Record the water heater’s exact make, model, fuel type, and relevant specifications.
- Check the installation manual for approved vent parts and layout requirements.
- Match the required vent diameter and material to the kit listing.
- Confirm whether the project needs a blower, vent system, termination, or outdoor accessory.
- Review which parts are included and identify any components not specified in the package.
- Ask a qualified professional or the appliance manufacturer when compatibility is unclear.
Gas-appliance venting affects safe operation. Product descriptions alone may not contain every installation detail. Follow the appliance manufacturer’s instructions and applicable local requirements, and use qualified installation help when needed.
Frequently Asked Questions
Is a power-vent blower the same as a vent kit?
No. A blower assembly is a component used in a power-vent appliance. A vent kit or vent pipe system consists of components that route or terminate exhaust. The Rheem SP21031A is described as a blower assembly, while the other products are venting accessories or systems.
Can I use the SP20285 kit with 3-inch vent pipe?
The listing specifies 2-inch PVC and ABS pipe only. It does not support treating the kit as suitable for 3-inch pipe. Confirm the required diameter in the appliance documentation.
Is the ThermoMate kit compatible with every gas tankless heater?
No universal compatibility is established by the supplied product details. The listing says it works with most standard 3-inch gas tankless water heaters. Check the specific heater’s approved vent requirements before use.
Which product is for an outdoor Rheem tankless installation?
The Rheem RTGH-X Outdoor Vent Kit is listed for Rheem high-efficiency tankless water heaters, specifically RTGH-3 models. Verify the exact model before ordering.
Can the Tjernlund VP-3F vent any gas water heater?
The listing specifies millivolt gas water heaters in the 60,000-to-120,000-BTU range. It should not be assumed to suit appliances outside those stated conditions without confirmation from the manufacturer.
What should I do if I cannot identify the correct replacement blower?
Check the water heater’s model label and compare the existing blower’s part number with the replacement documentation. The supplied information for the SP21031A does not name compatible heater models, so confirm fit with the appliance manufacturer or a qualified service professional.