Sioux Chief 832-4HHD
$26.26 at Amazon
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Hub drain
What it is, what’s allowed to drain into it, and how far above it each line must stop.
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Quick answer
A hub drain is an open pipe or hub at least 1 inch above the floor that takes indirect waste: relief valve, condensate and softener lines. Each line stops above it with an air gap or air break, and the hub drain itself is trapped and vented.
Hub drain fixture: Sioux Chief 832-4HHD$26.26 at AmazonPrice as of Oct 23, 2026, 5:30 AM EDT · low stock then
Check it on AmazonWhat a hub drain is
The plumbing code defines it in one line, and the rest of the rules come from what it’s for.
IPC section 802.4.2 says a hub drain is a hub or a pipe that sticks up at least 1 inch above a water-impervious floor. That raised lip is the whole point. It keeps floor water and mop water out, so only the pipes that are meant to drain into it do.
The code calls it a waste receptor. Receptors catch indirect waste: water from equipment that must never connect straight to the drain, because a backup could push sewage into it. Water heater relief valves, furnace and AC condensate, water softener regeneration and some boiler and process drains are the common ones in homes and light commercial work.
| Receptor | What it looks like | Code section | Typical use |
|---|---|---|---|
| Hub drain | A hub or pipe at least 1 in. above the floor | 802.4.2 | Relief valve, condensate, softener lines |
| Standpipe | A trapped pipe 18–42 in. above its trap weir | 802.4.3 | Clothes washer drain |
| Floor sink | A sunken basin set in the floor, often with a dome strainer | 802.4 (receptor) | Commercial kitchen equipment |
| Floor drain | A drain flush with the floor under a grate | Chapter 7 fixture | Floor water, spills, basements |
So is a hub drain a floor drain? Not in the code. A floor drain is flush and takes water off the floor. A hub drain rises above the floor and takes water from pipes. You’ll see the two combined, a floor drain with a hub or funnel extension on top, and that combination is common in mechanical rooms.
Can this line drain to a hub drain?
Pick the line and enter its pipe size. The checker gives the connection the code calls for and the minimum air gap.
The checker uses the 2018 IPC, which many states adopted with their own changes. Georgia, for example, amends the IPC. Ask your inspector before you plumb a new receptor, and keep the relief valve rules, which protect people, as the strict ones.
Air gap vs air break
IPC 802.3 says indirect waste discharges through an air gap or an air break into a waste receptor. They aren’t the same, and the line decides which you need.
An air gap is open air between the end of the pipe and the receptor’s flood level rim, at least twice the pipe’s effective opening (802.3.1). If the receptor backs up and overflows, the water spills on the floor before it can reach the pipe.
An air break lets the pipe end inside the receptor, below the rim but above the trap seal (802.3.2). It’s allowed for some nonpotable lines and gives less protection.
| Pipe end size | Minimum air gap | Relief valve line must end between |
|---|---|---|
| 1/2 in. | 1 in. | 1 in. and 6 in. above the rim |
| 3/4 in. | 1.5 in. | 1.5 in. and 6 in. above the rim |
| 1 in. | 2 in. | 2 in. and 6 in. above the rim |
| 1-1/4 in. | 2.5 in. | 2.5 in. and 6 in. above the rim |
| 1-1/2 in. | 3 in. | 3 in. and 6 in. above the rim |
| 2 in. | 4 in. | 4 in. and 6 in. above the rim |
The gap is measured to the flood level rim, the top edge where water would spill over, not to the water inside. On a hub drain that’s the top of the hub. A relief line that hangs inside the hub is a violation even though it’s “over the drain”.
Water heater relief valve lines and hub drains
The relief valve line, often called the T&P line, has the strictest rules because it carries scalding water under pressure. IPC 504.6 lists 14 requirements. These are the ones that matter at a hub drain:
| Rule (IPC 504.6) | What it means at the hub drain |
|---|---|
| 1. Not directly connected to the drainage system | Never glued or threaded into the hub |
| 2. Discharge through an air gap in the same room as the heater | The hub drain must be in the heater’s room |
| 3. Not smaller than the valve outlet, full size to the air gap | No reducing near the end |
| 5. To the floor, the pan, a waste receptor or outdoors | A hub drain is a waste receptor, so it’s allowed |
| 7. Readily observable termination | You should be able to see it drip |
| 8. Not trapped; 9. flows by gravity | No dips or traps in the line on the way down |
| 10. Ends ≤ 6 in. and ≥ 2× its diameter above the rim | 3/4 in. pipe: between 1-1/2 and 6 in. above the hub |
| 11. No thread on the end; 12. no valves or tees | Plain cut end, no shutoff, no shared line |
Rule 4 adds that each relief device gets its own line. Two heaters or a heater and a boiler can’t share one relief line, even if they share the hub drain. The relief valve guide covers the valve itself, and the drain pan guide covers IPC 504.7, the pan under the tank.
Condensate, softener and boiler lines
These are nonpotable clear-water waste under IPC 802.1.5, which allows an air break or an air gap. In practice most installers use an air gap anyway, because it’s easy to see and impossible to get wrong.
Several lines can share one hub drain if the receptor is big enough for all of them at once. IPC 802.4.1 says a receptor is sized for the maximum discharge of every line it serves, and installed so it doesn’t splash or flood. A softener regenerating at the same moment the relief valve opens is the case to plan for.
Where there’s no drain at the right height, a condensate pump lifts the water to one. The condensate pump guide covers sizes and safety switches.
Good hub drain setup
Every line ends above the rim with a visible gap, the hub is in the same room as the heater, and the hub is trapped, vented and easy to reach.
Common problems
A relief line pushed down inside the hub, a softener line taped into it, a hub drain boxed into a wall or ceiling, or several lines overflowing a small hub.
Which equipment needs which connection
| Equipment (IPC section) | Connection to the receptor |
|---|---|
| Food storage, prep and handling equipment (802.1.1) | Air gap; each sink compartment to the receptor on its own |
| Walk-in cooler or freezer floor drains (802.1.2) | Air gap; air break or air gap with a backwater valve |
| Sterilizers, relief valves, other potable clear water (802.1.3) | Air gap |
| Pool water, filter backwash, deck drains (802.1.4) | Air gap |
| Process tanks, filters, drips, boilers (802.1.5) | Air break or air gap |
| Commercial dishwashing machines (802.1.6) | Air gap or air break |
| Commercial pot, dish and utensil sinks (802.1.7) | Air gap or air break |
The pattern is simple. Anything that carries drinking water or touches food or pool water gets an air gap, because a backup into it would be a health problem. Equipment carrying water nobody drinks may use an air break. IPC 802.1 also says that in a home, food equipment isn’t on the list; a kitchen sink and a household dishwasher connect directly.
A worked example: three lines to one hub drain
| Line | Pipe end | Connection | Where it ends |
|---|---|---|---|
| Water heater relief valve | 3/4 in. | Air gap (504.6) | 1-1/2 to 6 in. above the rim |
| Furnace condensate | 3/4 in. | Air gap or air break (802.1.5) | 1-1/2 in. or more above the rim for an air gap |
| Softener regeneration | 1/2 in. | Air gap or air break (802.1.5) | 1 in. or more above the rim for an air gap |
| Water heater pan drain | 3/4 in. minimum | Indirect, full size (504.7.2) | Over the receptor, open end |
Four lines can land on one hub drain if the hub is wide enough for all four ends to stay apart and the receptor can take the flow if the relief valve and the softener discharge at once (802.4.1). The relief line has the tightest window, so set it first and fit the others around it.
The pan under the heater counts too. IPC 504.7.1 wants a pan at least 1-1/2 in. deep with a drain of at least 3/4 in., and 504.7.2 lets it end over an indirect waste receptor or floor drain, or outdoors 6 to 24 in. above the ground. A replacement heater doesn’t need a pan drain where none was installed before.
Does a hub drain need a trap and a vent?
Yes, in most cases. IPC 802.3 says waste receptors shall be trapped and vented and connect to the building drainage system. The exception is a receptor that takes only clear-water waste and doesn’t connect directly to a sanitary drain, which needn’t be trapped.
IPC 802.4 also wants a removable strainer or basket over a receptor’s outlet, except on hub drains that take only clear-water waste and on standpipes. And receptors can’t go in concealed spaces, plenums, crawl spaces, attics or the space above a ceiling; they need ready access.
A hub drain that sits dry for months can lose its trap seal like any floor drain. The trap primer guide covers when the code wants a primer or a seal device, and the sewer smell guide covers what happens when one dries out.
| Receptor takes | Trap | Vent | Strainer or basket |
|---|---|---|---|
| Any waste, connected to the sanitary drain | Required (802.3) | Required (802.3) | Required unless it’s a clear-water hub drain or a standpipe (802.4) |
| Clear-water waste only, not directly connected to a sanitary drain | Not required (802.3 exception) | Not required | Not required on a clear-water hub drain |
| Washer discharge (standpipe) | Individually trapped (802.4.3) | Required | Not required |
Hub drain or standpipe for a washer?
A clothes washer gets a standpipe, not a hub drain. IPC 802.4.3 says standpipes are individually trapped and extend 18 to 42 in. above the trap weir, with access for rodding. The height gives the washer’s pump a column to fill so it doesn’t overflow at the top.
A laundry tray can drain into the washer standpipe without its own trap, under 802.4.3.1. That’s a common basement setup and one more reason the standpipe has to be the right height. If the washer sits in a pan, the washing machine drain pan guide covers where the pan drains.
Standpipe done right
Its own trap, 18 to 42 in. above the trap weir, access for a snake, and the washer hose loose in the top, not sealed in.
Signs it’s wrong
Water spilling from the top during the spin cycle, a gurgle or smell from the pipe, or a hose taped airtight into it.
Floor sinks in commercial kitchens
Restaurants use floor sinks where homes use hub drains. IPC 802.1.1 says food storage, prep and handling equipment drains through an air gap, and each compartment of a multi-compartment sink discharges on its own to a receptor. Commercial dishwashers and pot sinks may use an air gap or air break under 802.1.6 and 802.1.7.
Walk-in cooler and freezer floor drains are indirect too, through an air gap (802.1.2). In a space that freezes, the line isn’t trapped and drains to a receptor outside the cold area.
Floor sinks are deeper and wider than a hub drain, with a strainer to catch food. Zurn’s FD2375 is a typical one: a 12 x 12 in. cast iron body with a white acid-resisting porcelain enamel interior, a 6 in. sump and an ABS anti-splash dome strainer.
| Zurn FD2375 option | What it changes |
|---|---|
| -NH2 / -NH3 / -NH4 | 2, 3 or 4 in. no-hub outlet |
| -F full grate | Covers the whole top; lines enter through the grate |
| -H 1/2 grate | Half open for indirect lines, half covered |
| -T 3/4 grate | Three quarters covered |
| -Y sediment bucket | A basket that lifts out to empty solids |
Zurn calls the FD2375 recommended for sanitary installations. The grate choice is about how many lines come down and where: a half grate leaves room for several pipe ends with a visible gap, a full grate suits a floor where people walk.
For floor water there’s the plain floor drain. Zurn’s FD-2220 is a medium-duty drain recommended for light vehicle traffic and residential use, with a PVC or ABS body and a cast iron frame and grate, in 2, 3 or 4 in. hub sizes. Zurn makes each size in PVC and ABS, so match the body to the drain pipe you’re tying into.
It sits flush, so it can’t give a pipe end the 1 in. rise a hub drain has. Where both jobs land in one spot, installers fit a funnel or hub extension over a floor drain so lines get their air gap and the floor still drains.
Whichever receptor you use, it still has a trap that can dry out between discharges. A relief valve may never open, and a softener only runs every few days, so the trap seal in a mechanical room hub drain can go dry. That’s why the trap and primer rules above apply to it like any other drain.
Three receptors, compared
One of each receptor type, plus a seal for one that dries out. Each was new and in stock on the day of the update. Prices come from Amazon with the time they were read.
Zurn FD2375 floor sink
$112.99 at Amazon
Check it on AmazonPrice as of Oct 23, 2026, 5:30 AM EDT
Zurn FD2220 floor drain
$54.79 at Amazon
Check it on AmazonPrice as of Oct 23, 2026, 5:30 AM EDT
Oatey Drain Seal 3 in.
$25.58 at Amazon
Check it on AmazonPrice as of Oct 23, 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.
| Receptor | Key specs | Pick it if | Skip it if |
|---|---|---|---|
| Sioux Chief 832-4HHD | Hub drain finish fixture: ABS base, PVC hub riser 2-3/4 in. tall, 4-7/8 in. O.D.; fits the 6-1/2 in. FinishLine coring sleeve | You set a FinishLine rough-in in the slab and need a hub for condensate or relief lines. | There’s no FinishLine rough-in. It’s a finish fixture, not a full drain. |
| Zurn FD2375-NH3-H | 12 x 12 in. cast iron, enameled interior, 6 in. sump, 3 in. no-hub outlet, half grate, dome strainer | Kitchen equipment needs an air gap receptor that catches solids. | It’s a home mechanical room. A hub drain is simpler. |
| Oatey Drain Seal, 3 in. | One-way valve insert; Oatey says it blocks odors, insects and rodents and opens when water flows | A floor drain or floor-level receptor sits dry for weeks and smells. | Your pipe is 2 in. Oatey says to match the seal to the pipe size. |
| Zurn FD2220-PV3-NT | Medium-duty floor drain, PVC body, 3 in. PVC hub, nickel top | You need to take water off the floor in a basement or garage. | You need a raised hub for pipes. Floor drains sit flush. |
Sioux Chief’s spec sheet says the 832 Series allows adjustment after the concrete pour. It threads into the FinishLine rough-in’s coring sleeve once the coring plug comes out, which is why it isn’t a complete drain by itself. An optional 832-UM stainless mesh debris basket fits the 4HHD model. The riser is 2-3/4 in. tall, which easily clears the code’s 1 in. minimum.
I’ve used each of these. For a new slab with a water heater and a furnace, the FinishLine hub drain is the cleanest way to get a code-height hub exactly where the lines come down.
Oatey describes its Drain Seal as a one-way valve for drains that see little use, made for 2 or 3 in. outlets; it opens when water flows and closes when it stops. It suits a floor drain or a floor sink that sits dry. A hub drain whose lines stop above the rim is easier to keep wet: pour water in at each service visit.
Where to put a hub drain
- 1Same room as the water heater
The relief valve line has to end in the heater’s room (504.6), so the hub drain goes there too.
- 2Where you can see it
504.6 wants the relief termination readily observable. A drip into a visible hub tells you the valve is leaking.
- 3Never concealed
802.4 bans receptors in concealed spaces, plenums, crawl spaces, attics and above ceilings.
- 4Sized for every line
802.4.1: big enough for all the lines discharging at once, without splashing or flooding.
- 5Lines short and direct
802.3: an indirect waste pipe longer than 30 in. horizontally or 54 in. in total developed length has to be trapped.
Setting a FinishLine hub drain in a slab
- 1Set the rough-in
The FinishLine rough-in base and coring sleeve go in with the underground, trapped and vented like any receptor.
- 2Pour around it
The coring plug keeps concrete out of the sleeve during the pour.
- 3Remove the coring plug
Sioux Chief’s sheet says the finish fixture threads in after the plug comes out.
- 4Thread in the hub fixture
The 832-4HHD has ACME threads that set its height after the pour, to match the finished floor.
- 5Add the debris basket if wanted
The optional 832-UM stainless mesh basket fits the 4HHD model.
The 4HHD model goes with the 6-1/2 in. coring sleeve and the 3HHD with the 5-1/2 in. sleeve. Sioux Chief lists the 4HHD at 5-1/4 in. overall with a 2-3/4 in. hub riser, 4-7/8 in. across. Match the fixture to the sleeve size before you order.
Keeping a hub drain working
Once a season
Pour a bucket of water in to refill the trap, clear debris off the strainer or basket, and look at each line end for a steady drip.
A relief line that drips
A steady drip from the T&P line means the valve is opening. That’s a water heater problem to fix, not something to plumb around.
That visible drip is the reason the code wants the relief line to end where people can see it. Hidden inside a pipe, a leaking relief valve can run for months. Condensate lines also grow algae and slime that can block the line before it reaches the hub; clearing them is part of the furnace and AC service.
Hub drain mistakes inspectors see
| What people do | What the code says |
|---|---|
| Push the relief line down into the hub | 504.6 wants an air gap: the end at least twice its diameter above the rim. |
| Glue a condensate line into the hub | 802.3: indirect waste discharges through an air gap or air break, never a direct joint. |
| Put a threaded cap or valve on the relief line | 504.6 bans a threaded end, valves and tees. |
| Hide the hub drain behind drywall | 802.4: no receptors in concealed spaces; they need ready access. |
| Drain a washer into a short hub | 802.4.3: a washer gets a standpipe 18–42 in. above its trap weir. |
Questions people ask
What is a hub drain?
A waste receptor shaped like a hub or a pipe that rises at least 1 inch above a water-impervious floor (IPC 802.4.2). It takes indirect waste such as relief valve, condensate and softener lines.
What is the difference between a floor sink and a hub drain?
Both are waste receptors. A floor sink is a sunken basin with a strainer, used for commercial kitchen equipment. A hub drain is a raised hub, used mostly for relief valve and condensate lines.
Does a hub drain need to be vented?
Yes in most cases. IPC 802.3 says waste receptors are trapped and vented. A receptor taking only clear-water waste that doesn’t connect directly to a sanitary drain needn’t be trapped.
Is a hub drain considered a floor drain?
No. A floor drain sits flush to take water off the floor. A hub drain rises at least 1 inch above the floor and takes water from pipes.
Can a water heater relief valve drain to a hub drain?
Yes, through an air gap in the same room. IPC 504.6 lists a waste receptor as an allowed discharge point; the pipe ends between twice its diameter and 6 inches above the rim.
Can a hub drain be inside a wall or closet?
Not inside a wall. IPC 802.4 bans receptors in concealed spaces, plenums, crawl spaces and attics, and wants ready access. A mechanical closet with a door is fine.
Can a water heater pan drain to a hub drain?
Yes. IPC 504.7.2 lets the pan drain end over an indirect waste receptor or floor drain, full size, with a drain of at least 3/4 inch.
How high above a hub drain should a condensate line end?
With an air gap, at least twice the pipe’s opening above the rim: 1-1/2 inches for a 3/4-inch line. The code also allows an air break for condensate.
How I put this together
Why trust me
I’m Isaac Daniels, a licensed journeyman plumber in Georgia (license #JP507711). I’ve used each product listed here. The rules come from the 2018 International Plumbing Code, chapters 5 and 8, and the product details from Sioux Chief and Zurn spec sheets, read Oct 23, 2026.
How I pick
- One receptor of each type, so you can compare them, plus one trap seal.
- Genuine branded parts with published spec sheets, new and in stock on the day of the update.
- No scores: a hub drain, a floor sink and a floor drain do different jobs.
- Prices come from Amazon’s API with the time they were read.
Sources
- International Code Council, 2018 International Plumbing Code, chapter 8, sections 802.1 through 802.4.3.1 (codes.iccsafe.org).
- International Code Council, 2018 International Plumbing Code, section 504.6 (relief valve discharge) and 504.7 (pans).
- Sioux Chief, 832 Series FinishLine adjustable hub drain fixture specification sheet, and 832-4HHD product page (siouxchief.com).
- Oatey, “Why Does My House Smell Like Sewer Gas? (And How to Fix It)” (oatey.com blog), Drain Seal description.
- Zurn, FD2375 floor sink specification sheet (Rev. D, 02/24/25) and FD-2220 medium-duty floor drain specification sheet (zurn.com).
- Product listing details for the three receptors (Amazon Creators API, Oct 23, 2026).