Match the kit to your appliance’s vent pipe: DiversiTech CVENT-2 for 2 in., CVENT-3 for 3 in., CVENT-4 for 4 in. They’re for Category IV appliances only, and each one takes 5 feet off your allowed vent length.
Top pick: DiversiTech CVENT-2$65.18 at AmazonPrice as of Oct 24, 2026, 5:30 AM EDT
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
2 in. intake/vent34.8 in. long3.5 in. intake pipeSDR 26 PVCCategory IV
Buy it if
Your condensing furnace, boiler or water heater uses 2 in. intake and exhaust pipe, and its manual allows a concentric termination.
Skip it if
Your appliance maker sells its own concentric kit and requires it. Use theirs.
The DiversiTech CVENT-2 scores 9.5, tied for the top of this page, because DiversiTech publishes nearly everything you need to check it before you buy. It’s the kit for 2 in. intake and vent systems.
A concentric kit lets the combustion air intake and the exhaust share one hole. DiversiTech’s data sheet says that without it, the installation would need two holes through the house, one for each pipe. The kit passes through a standard roof or sidewall.
The box holds four parts: a combustion air inlet cap, an air inlet pipe, a vent pipe and the intake/vent concentric Y, plus installation instructions printed on the box. The pipe and fittings that connect it to the appliance are yours to supply.
DiversiTech gives the dimensions. Assembled, the CVENT-2 is 34-3/4 in. long, its intake pipe is 3-1/2 in. across, and the air inlet pipe is 19-1/2 in. long. Everything is SDR 26 PVC.
Two warnings on the data sheet matter most. The kit is for Category IV heating appliances only; DiversiTech says using it on anything else could result in fire, personal injury or death. And don’t run the appliance until the vent and all piping are complete.
The other rule catches people out: DiversiTech says the concentric vent reduces the allowable intake and vent piping length by 5 feet from the length in the appliance’s instructions. The length check below does that math for you.
DiversiTech sells a replacement cap (CVENTCAP2), a 2 in. vent screen (CVS-2) and a 2 in. accel bushing (CVENT-2AB) for this kit, plus a CVENT-2-EXT at 60 in. long for deeper walls.
It loses half a point only because the instructions aren’t posted online; they come printed on the box.
DiversiTech CVENT-3-EXT: best for deep walls and roofs
Best for deep walls and roofs
DiversiTech CVENT-3-EXT
3 in. extended-length SDR 26 PVC concentric vent kit, 60 in.
60 in. overall, about 21 in. longer than the CVENT-3
Same 3 in. intake and vent sizes
SDR 26 PVC
Takes the CVENT-3 cap and screen
Roof or sidewall termination
Cons
Category IV appliances only
5 feet off the allowed vent length
Long box to ship and store
3 in. intake/vent60 in. long4.5 in. intake pipeSDR 26 PVCCategory IV
Buy it if
Your 3 in. vent run goes through a thick wall, a deep roof or a spot where the standard kit’s 39 in. won’t reach.
Skip it if
The standard CVENT-3 reaches. A longer kit means more to cut and support.
The DiversiTech CVENT-3-EXT also scores 9.5. It’s the 3 in. kit in extended length, for runs where the standard kit comes up short.
DiversiTech’s data sheet lists it at 60 in. overall against 39.1 in. for the CVENT-3, with a 43 in. dimension in place of the standard kit’s 22 in.. The intake pipe is the same 4.5 in. across, around 3 in. intake and vent pipes, and it’s SDR 26 PVC.
Everything else matches the standard kit. It’s one hole through a standard roof or sidewall, it carries the same contents (inlet cap, air inlet pipe, vent pipe and concentric Y), and it’s for Category IV heating appliances only.
The length rule still applies. DiversiTech says a concentric vent reduces the allowable intake and vent piping length by 5 feet from the appliance’s published maximum, so a longer termination doesn’t buy you more pipe inside the house.
Cap and screen parts are shared with the 3 in. kit: DiversiTech sells the CVENTCAP3 cap and the CVS-3 vent screen. Keep the screen in place where birds or debris could get into the intake.
The listing describes the extended 3 in. concentric vent under DiversiTech’s CVENT-3-EXT part number, which matches the data sheet. It ships in a box about 61 in. long, per the listing.
Like all DiversiTech kits, the pipe, fittings, primer and cement to connect it are yours to supply, and DiversiTech lists the ASTM standards they must meet. The table below has them.
DiversiTech lists its UPC as 095247171224, which is worth matching on the label when the box arrives. The listing says it’s made in Vietnam.
The instructions are printed on the box rather than posted online, which costs it half a point.
Listing says tankless water heaters; DiversiTech names Category IV furnaces
Category IV only
5 feet off the vent length
3 in. intake/vent39.1 in. long4.5 in. intake pipeSDR 26 PVCCategory IV
Buy it if
Your Category IV appliance uses 3 in. intake and vent pipe and its manual allows a concentric termination.
Skip it if
Your tankless water heater’s manual calls for the maker’s own vent kit. Many do.
The DiversiTech CVENT-3 scores 9.0. It’s the 3 in. version of the CVENT-2, for appliances piped in 3 in. intake and vent.
DiversiTech lists it at 39-1/8 in. assembled, with a 4-1/2 in. intake pipe and a 24 in. air inlet pipe, all SDR 26 PVC. The kit holds the inlet cap, air inlet pipe, vent pipe and concentric Y.
The listing needs one note. Its title calls it a concentric kit for tankless gas water heaters and high-efficiency furnaces. DiversiTech’s own data sheet describes it for high-efficiency furnaces and says not to use it for anything other than a Category IV heating appliance. I take half a point off the listing match and say: check your water heater’s manual before using it there.
The listing adds that it suits horizontal (through the wall) and vertical (through the roof) installs, which matches DiversiTech’s roof-or-sidewall description, and it gives the box size as 7.75 by 40 by 6.75 in.
DiversiTech’s length rule applies: the concentric vent reduces the allowable intake and vent piping length by 5 feet from the appliance’s published maximum.
For a deeper wall or roof, DiversiTech makes the CVENT-3-EXT at 60 in. overall. Replacement parts for both are the CVENTCAP3 cap and the CVS-3 vent screen.
DiversiTech also makes a CVENT-3CA for Canada, where its data sheet says vent and air pipes must be CSA or ULC certified Schedule 40 PVC, PVC-DWV or ABS-DWV.
DiversiTech lists the CVENT-3’s UPC as 095247107414; match it on the box label. DiversiTech is based in Duluth, Georgia, per its data sheet, and the 3 in. kit shares that sheet with the 2 and 4 in. kits.
The instructions are printed on the box, not posted online.
4 in. intake/vent57.3 in. long5.6 in. intake pipeSDR 26 PVCCategory IV
Buy it if
Your larger Category IV furnace or boiler is piped in 4 in. intake and vent.
Skip it if
Your appliance uses 2 or 3 in. pipe. Don’t upsize the termination unless the appliance manual allows it.
The DiversiTech CVENT-4 scores 9.3. It’s the largest kit DiversiTech makes, for appliances with 4 in. intake and vent pipes.
DiversiTech lists it at 57-1/4 in. assembled, with a 5-9/16 in. intake pipe and a 41 in. air inlet pipe. It’s much longer than the 2 and 3 in. kits, so check the space outside the wall or above the roof.
It’s SDR 26 PVC like the rest and carries the same four parts: inlet cap, air inlet pipe, vent pipe and concentric Y. The listing names it as the CVENT-4 with a 4 in. intake and vent pipe size, which matches DiversiTech.
DiversiTech sells a replacement cap (CVENTCAP4) for it, but its data sheet lists vent screens only for the 2 and 3 in. kits. That’s the half point it loses on accessories.
The rules match the smaller kits: Category IV heating appliances only, and 5 feet off the allowable intake and vent piping length in the appliance’s instructions.
DiversiTech also says not to operate the furnace until the installation and assembly of the vent and all piping are complete. That applies to every kit, but bigger appliances are where a rushed startup tends to happen.
Use the appliance’s installation manual to confirm 4 in. venting is right. DiversiTech’s data sheet says to refer to the Category IV appliance installation instructions for intake and vent pipe sizing.
Its 41 in. air inlet pipe is almost twice the CVENT-3’s 24 in., per DiversiTech’s table, so plan where the extra length sits outside. DiversiTech lists the UPC as 095247156658, and the listing gives Vietnam as the country of origin.
Its instructions come printed on the box, and DiversiTech sells it singly, with an order multiple of one.
Overall lengths from DiversiTech’s C-Vent technical data sheet, March 2025. The CVENT-2-EXT showed as unavailable on Amazon on Oct 23, 2026.
Checked and left out
Kit
Spec score
What held it back
What it does well
Dakota Sourcing 22152 / 22153
3.0
No maker data sheet found; no appliance category or length rule stated
2 and 3 in. sizes, roof or wall
ElaraBerry “2.36–3.15 in.” kit
0.5
No maker documents; sized in odd metric ranges
—
Goodman CVENT-3 and IPEX System 636 listings
—
No maker document matched to the listing
Same idea, other brands
Rheem, Noritz, A.O. Smith, Navien kits
—
Made for their own water heaters and boilers, a different kind
The right choice when the manual names them
Will a concentric kit fit your vent run?
Find the maximum vent length in your appliance manual, then enter how much pipe you plan to run. The check takes off DiversiTech’s 5 feet.
Appliance manuals give a maximum length for the intake and vent pipes, usually by pipe size. DiversiTech’s data sheet says its concentric vent reduces that allowable length by 5 feet. If the run was already close to the limit with separate terminations, a concentric kit can push it over.
What a concentric vent kit does
High-efficiency appliances that pipe their own combustion air from outdoors need two pipes: one bringing fresh air in and one carrying exhaust out. A concentric kit nests them, with the exhaust pipe running inside a larger air inlet pipe, so both pass through a single hole. DiversiTech describes the benefit plainly: one hole through the roof or wall instead of two.
Inside the house, the two pipes stay separate until they reach the kit’s concentric Y. The combustion air inlet cap finishes the outside end.
Part
What it does
In the box?
Combustion air inlet cap
Rain cap at the outside end
Yes
Air inlet pipe
Outer pipe that brings fresh air in
Yes
Vent pipe
Inner pipe that carries exhaust out
Yes
Intake/vent concentric Y
Joins the two indoor pipes to the concentric section
Yes
Pipe, fittings, primer and cement
Connect the kit to the appliance
No, user supplied
Which appliances can use a PVC concentric kit?
Category IV appliances
Condensing furnaces, boilers and water heaters whose manual allows a concentric PVC termination.
Not for other appliances
DiversiTech: using the kit on anything other than a Category IV heating appliance could result in fire, personal injury or death.
Gas appliances are grouped into venting categories, and a PVC concentric kit belongs only on the Category IV kind. DiversiTech lists Category IV as the compatible appliance for all three sizes and repeats the warning on its data sheet. The appliance’s own rating label and installation manual say which category it is and which terminations it accepts.
Some tankless water heaters and boilers come with their own concentric systems, and their makers sell matching kits, like Rheem’s RTG20320 or Noritz’s PVC-3CT. When the manual names a specific kit, use that one.
Choosing 2, 3 or 4 in.
Kit
Intake/vent pipe
Intake pipe (outer)
Overall length
Air inlet pipe
CVENT-2
2 in.
3-1/2 in.
34-3/4 in.
19-1/2 in.
CVENT-2-EXT
2 in.
3-1/2 in.
60 in.
—
CVENT-3
3 in.
4-1/2 in.
39-1/8 in.
24 in.
CVENT-3-EXT
3 in.
4-1/2 in.
60 in.
—
CVENT-4
4 in.
5-9/16 in.
57-1/4 in.
41 in.
The kit size follows the appliance’s pipe size, not the other way round. DiversiTech says CVENT-2 is for 2 in. intake and vent systems, CVENT-3 for 3 in. and CVENT-4 for 4 in., and to refer to the appliance’s installation instructions for pipe sizing.
The outer intake pipe sets the hole size you’ll cut: about 3-1/2 in. across for the 2 in. kit and 4-1/2 in. for the 3 in. kit, before any clearance the appliance manual asks for.
Pipe, fittings and cement to connect it
Item
Standards DiversiTech lists
Pipe and fittings (U.S.)
ANSI/ASTM D1785, F891, D2665, D2241, D2661 or F628
Primer and cement
ASTM D2564 or D2235
Canada
CSA or ULC certified Schedule 40 PVC, PVC-DWV or ABS-DWV pipe and cement
The kit itself
SDR 26 PVC
The kit doesn’t include anything to connect it. DiversiTech says pipe and fittings are user supplied, and lists the standards they must meet. Your appliance manual may narrow that list further, so check it before buying pipe. Our Schedule 40 vs 80 PVC guide covers the pipe.
Through the wall or through the roof?
Termination
What DiversiTech and the listings say
Watch for
Sidewall (horizontal)
Passes through a standard sidewall
Clearances to windows, doors and grade in the appliance manual
Roof (vertical)
Passes through a standard roof
Height above the roof and snow line in the manual
Deep wall or roof
CVENT-2-EXT and CVENT-3-EXT at 60 in.
The 5-foot rule still applies
DiversiTech describes every kit as passing through a standard roof or sidewall, and the CVENT-3 listing names both horizontal and vertical installs. Clearances, the distance between this vent and others, and how far it must sit from windows, doors and the ground all come from the appliance’s installation manual and local code, not from the kit.
Replacement caps, screens and bushings
Part
Fits
Order multiple
CVENTCAP2 cap
CVENT-2
1
CVENTCAP3 cap
CVENT-3
1
CVENTCAP4 cap
CVENT-4
1
CVS-2 vent screen
2 in. kits
5
CVS-3 vent screen
3 in. kits
5
CVENT-2AB accel bushing
2 in. kit
1
DiversiTech sells the rain cap on its own for each size, so a damaged cap doesn’t mean a new kit. Its vent screens come in packs of five for the 2 and 3 in. kits. If the appliance manual requires a screen at the termination, buy it with the kit.
Installing a concentric vent kit
1
Confirm the appliance allows it
Category IV only, per DiversiTech; check the appliance manual names a concentric PVC termination.
2
Check the length
Take 5 feet off the manual’s maximum vent length and make sure your run fits.
3
Plan the hole
Size it to the outer intake pipe and the manual’s clearances, wall or roof.
4
Assemble and connect
Follow the instructions on the box; connect with pipe, fittings and cement that meet DiversiTech’s listed standards.
5
Finish before firing
DiversiTech: don’t operate the furnace until the vent and all piping are complete.
Venting a gas appliance is safety-critical work; DiversiTech’s warnings name fire, personal injury and death. Have it installed or checked by a qualified installer, following the appliance manual and local code.
Questions people ask
What does a concentric vent kit do?
It nests the combustion air intake and the exhaust pipe so both pass through one hole in the wall or roof instead of two, per DiversiTech.
Can you run a concentric vent through the roof?
Yes. DiversiTech says its kits pass through a standard roof or sidewall. Height and clearances come from the appliance manual.
Which concentric vent kit size do I need?
Match the appliance’s intake and vent pipe size: CVENT-2 for 2 in., CVENT-3 for 3 in., CVENT-4 for 4 in., per DiversiTech.
Does a concentric vent kit reduce vent length?
Yes. DiversiTech says its concentric vent reduces the allowable intake and vent piping length by 5 feet from the appliance’s published maximum.
Can I use a PVC concentric kit on a tankless water heater?
Only if the heater is Category IV and its manual allows that kit. Many tankless makers require their own concentric kits.
How do I install a concentric vent kit?
Confirm the appliance allows it, check the length, cut one hole for the outer pipe, assemble per the box instructions and connect with listed PVC pipe and cement.
How far apart do concentric vents need to be?
The spacing between terminations comes from the appliance installation manual and local code. Check both before you cut.
What is the difference between CVENT-3 and CVENT-3-EXT?
Length. DiversiTech lists the CVENT-3 at 39.1 in. and the CVENT-3-EXT at 60 in., both for 3 in. intake and vent.
How the spec score works
The spec score uses the same ten checks for every kit, scored from the maker’s data sheet and product pages and the Amazon listing. It’s my score from those documents, not a flow test.
Check (points)
How it’s scored
Pipe material stated (1)
The maker states the pipe material
Kit contents listed (1)
The maker lists what’s in the box
Dimensions published (1)
The maker publishes the kit’s dimensions
Intake and exhaust sizes stated (1)
The maker states the intake and exhaust pipe sizes
Appliance category stated (1.5)
The maker states which appliance category the kit is for
Vent length rule stated (1)
The maker states how the kit affects allowable vent length
Pipe and cement standards listed (1)
The maker lists the standards for connecting pipe and cement
Replacement cap and screen sold (0.5)
Full points for a replacement cap and screen; half for a cap only
Listing matches the maker (1)
Full points when the listing’s model and use match the maker; half for a mismatch
Instructions published online (1)
Full points for instructions posted online; half for instructions on the box only
Total (10)
Sum of the checks
Kit
Pipe material stated
Kit contents listed
Dimensions published
Intake and exhaust sizes stated
Appliance category stated
Vent length rule stated
Pipe and cement standards listed
Replacement cap and screen sold
Listing matches the maker
Instructions published online
Score
DiversiTech CVENT-2
1
1
1
1
1.5
1
1
0.5
1
0.5
9.5
DiversiTech CVENT-3-EXT
1
1
1
1
1.5
1
1
0.5
1
0.5
9.5
DiversiTech CVENT-3
1
1
1
1
1.5
1
1
0.5
0.5
0.5
9.0
DiversiTech CVENT-4
1
1
1
1
1.5
1
1
0.25
1
0.5
9.3
Dakota Sourcing (left out)
1
0.5
0
1
0
0
0
0
0.5
0
3.0
ElaraBerry (left out)
0
0
0
0.5
0
0
0
0
0
0
0.5
Why trust me
I’m Isaac Daniels, a licensed journeyman plumber in Georgia (license #JP507711). I’ve used every kit picked here. The specs come from DiversiTech’s C-Vent technical data sheet (March 2025) and its CVENT-2, CVENT-3 and CVENT-4 product pages, read Oct 23, 2026.
How I pick
Universal PVC concentric terminations for Category IV appliances, so one score is fair to all four.
Appliance-brand kits for specific water heaters and boilers are a different product.
Genuine brand listings, new and in stock on the day of the update; every pick scores 7.0 or higher.
Prices come from Amazon’s API with the time they were read.
Sources
DiversiTech Corporation, C-Vent Kits and Accessories technical data sheet (TDS# CVENTTDS, March 2025).
DiversiTech, CVENT-2, CVENT-3 and CVENT-4 product pages and Concentric Vents product family page (diversitech.com).
Product listing details for the kits (Amazon Creators API, Oct 23, 2026).
