Quick Answer: The right tankless water heater vent kit depends on your brand and whether your unit condenses. For condensing units, buy the OEM-matched PVC concentric kit — Rinnai 196116PVC for Rinnai, Navien VK3HPVC for Navien, or the Rheem SP20245 (roughly $58) for Rheem EcoSense models. If you want one system with documented cross-brand approval instead of a single manufacturer’s accessory, DuraVent’s PolyPro line is approved for Navien’s full lineup and works with Rinnai and A.O. Smith’s condensing units too. Non-condensing units can’t use PVC or polypropylene at all — they need a stainless steel kit like the Rheem RTG20282 (about $127), rated for the 300°F+ exhaust that would melt plastic pipe.
Most people shopping for a tankless vent kit already own the heater and just need the pipe to finish the install — but the vent aisle at a big-box store or plumbing wholesaler mixes PVC, polypropylene, and stainless kits from half a dozen brands without making clear which one fits which unit. Buy the wrong material and you have a code violation and a carbon monoxide risk; buy the wrong brand’s concentric adapter and it simply won’t seat on your heater’s flue collar. This roundup sorts the OEM options by brand, names the closest thing to a universal pick, and flags the stainless kit non-condensing owners need instead.
The rule that decides everything: condensing status first, brand second
Condensing tankless water heaters (typically 0.90+ UEF) exhaust cool enough — roughly 100-140°F — for PVC or polypropylene vent pipe. Non-condensing units exhaust at 300°F+ and require Category III stainless steel, full stop. That single fact eliminates most of the vent aisle before brand even matters. Once you know your material, the second question is fit: OEM concentric kits are built to that manufacturer’s specific flue collar and termination hardware, so a Rinnai kit won’t drop cleanly onto a Navien unit even though both are PVC-rated condensing systems. For the full material and code-clearance breakdown, see our tankless water heater venting guide.
Our top picks at a glance
| Kit | Material | Fits | Config | Price |
|---|---|---|---|---|
| Rinnai 196116PVC | PVC (condensing) | Rinnai condensing units | 3" concentric | ~$65-$99 |
| Navien VK3HPVC | PVC (condensing) | Navien condensing units | 3" concentric | ~$60-$90 |
| Rheem SP20245 | PVC (condensing) | Rheem EcoSense condensing | 3" concentric | ~$58 |
| DuraVent PolyPro | Polypropylene (condensing) | Navien (full line), Rinnai, A.O. Smith | 2"/3" concentric or twin-pipe | varies by run length |
| Rheem RTG20282 | Stainless steel | Non-condensing units, any brand fit-dependent | 3"x5" concentric | ~$127 |
1. Rinnai 3-in. PVC Concentric Termination Vent Kit (196116PVC) — Best for Rinnai Condensing Units
Rinnai 196116PVC Concentric Termination Vent Kit
- Sized and fitted for Rinnai's condensing tankless flue collar — the adapter, gasket, and hardware are built for a Rinnai unit specifically, not a universal fit.
- Rinnai's condensing lineup is rated for 2-inch PVC runs up to 65 equivalent feet, so this termination kit pairs with standard Schedule 40 PVC pipe purchased separately for longer runs.
- Related Rinnai plastic concentric kits (like the 229013NPP horizontal termination kit for Sensei SE+ models) run closer to $99, so match the exact kit to your specific Rinnai model series before ordering.
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If you already own a condensing Rinnai unit, this is the default buy — it’s the manufacturer’s own accessory, built to seat on Rinnai’s flue collar without adapters or workarounds. The tradeoff versus the universal PolyPro option below is flexibility: it’s sized for Rinnai’s specific termination style, so if you later switch brands or need an unusual run configuration, you’re buying a new kit rather than extending an existing polypropylene system.
2. Navien VK3HPVC 3-in. PVC Concentric Vent Kit — Best for Navien Condensing Units
Navien VK3HPVC Concentric Vent Kit
- Genuine Navien accessory, sold through plumbing wholesalers and parts retailers, matched to the NPE and NPN series flue collar dimensions.
- Navien's condensing units are also approved for DuraVent PolyPro polypropylene venting across the full lineup, so owners who want a longer or more flexible run than the stock concentric kit supports have a documented alternative rather than an off-label workaround.
- Confirm your exact Navien model series before ordering — NPE and NPN venting hardware isn't always cross-compatible even within the Navien lineup.
This is the safe default for Navien owners for the same reason the Rinnai kit is the default for Rinnai owners: it’s built to the manufacturer’s own flue collar, so there’s no adapter guesswork. If your install needs a longer run than the stock kit’s straight-run length covers, the PolyPro option below extends further without abandoning OEM-approved materials.
3. Rheem SP20245 3-in. PVC Concentric Vent Termination Kit — Best Value
Rheem SP20245 Concentric Vent Termination Kit
- The least expensive OEM concentric kit in this roundup, at roughly $58 — noticeably cheaper than comparable Rinnai and stainless-steel options.
- Rated for Rheem's EcoSense high-efficiency condensing tankless gas water heaters, installable horizontally or vertically depending on your termination point.
- Rheem also sells a 3-in./5-in. stainless steel concentric kit (RTG20282, ~$127) for its mid-efficiency, non-condensing gas units — don't confuse the two if you own an older non-condensing Rheem model; see pick #5 below.
If cost is the deciding factor and you own a Rheem EcoSense condensing unit, this is the pick — same OEM-matched fit as the Rinnai and Navien kits above, at the lowest price point of the three.
4. DuraVent PolyPro Venting System — Best Cross-Brand Option
DuraVent PolyPro Polypropylene Venting System
- DuraVent publishes documented approval for the entire Navien condensing lineup, and polypropylene venting is separately approved for Rinnai's and A.O. Smith's condensing tankless units.
- Sold as a starter kit (adapter, initial pipe length, termination) plus additional straight-pipe sections priced separately, which makes it the more flexible choice for runs that don't match a single OEM kit's fixed length.
- Not a substitute for stainless steel on non-condensing units — polypropylene shares PVC's 100-140°F temperature ceiling, so it's condensing-only just like every other plastic option here.
- Because it isn't tied to one manufacturer's flue-collar geometry, confirm the specific adapter model matches your heater's exhaust outlet diameter before ordering — 2-inch and 3-inch systems aren't interchangeable.
This is the pick if you want one venting system with cross-brand documentation behind it, rather than a single manufacturer’s accessory — useful if you’re not fully committed to one brand yet, or if your run length doesn’t cleanly match any single OEM kit’s fixed configuration.
5. Rheem RTG20282 3-in./5-in. Stainless Steel Concentric Vent Kit — For Non-Condensing Units
Rheem RTG20282 Stainless Steel Concentric Termination Kit
- Rated for the 300°F+ flue-gas temperature a non-condensing tankless unit produces — PVC and polypropylene aren't an option here at any price.
- Includes flashing, cap, and storm collar for a roof or wall penetration, which is why it costs more than the PVC kits above: stainless material and the extra weatherproofing hardware both add cost.
- Sized for Rheem's mid-efficiency non-condensing lineup specifically; other brands' non-condensing units need their own manufacturer-matched stainless kit rather than this one, since flue collar dimensions vary by brand the same way they do on the condensing side.
If you’re not sure whether your unit condenses, check the UEF rating on the nameplate or spec sheet before buying anything in this roundup — a UEF around 0.80-0.82 means non-condensing and stainless steel, while 0.90+ means condensing and PVC or polypropylene are fair game.
How to choose
- You own a condensing Rinnai unit: the Rinnai 196116PVC (or the matching kit for your specific Rinnai series) is the OEM-safe default.
- You own a condensing Navien unit: the Navien VK3HPVC is the OEM match; the DuraVent PolyPro system is a documented, approved alternative if you need a longer or differently configured run.
- You own a Rheem EcoSense condensing unit and cost matters: the Rheem SP20245 is the cheapest OEM-fitted kit in this roundup at roughly $58.
- You’re not committed to a single brand’s accessory line, or your run doesn’t match a stock kit length: DuraVent PolyPro gives you documented cross-brand approval and modular pipe lengths instead of a fixed kit.
- Your unit is non-condensing (UEF around 0.80-0.82): skip every PVC and polypropylene option above and buy a stainless steel kit like the Rheem RTG20282 — material choice isn’t optional here.
- You’re unsure which type you have: check the UEF rating on your unit’s nameplate before ordering anything; see our tankless water heater venting guide for the full condensing-vs-non-condensing breakdown and code-clearance rules.
The bottom line
Buy your tankless water heater vent kit by condensing status first, brand second. Condensing units take PVC or polypropylene — the Rinnai 196116PVC, Navien VK3HPVC, and Rheem SP20245 are the OEM-matched picks for their respective brands, while DuraVent’s PolyPro system is the closest thing to a documented, cross-brand universal option. Non-condensing units need stainless steel, no exceptions — the Rheem RTG20282 is a solid example, but confirm brand-specific fit before buying since flue collar dimensions vary the same way they do on the condensing side. Get the material wrong and it’s a code and safety issue; get the brand fit wrong and the kit simply won’t seat. Venting is one of two accessory kits every install needs — pair it with an isolation valve kit so you can actually flush the unit once it’s vented and running.