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Most standard 275- and 330-gallon IBC tanks use a 2-inch (DN50) bottom outlet valve. The outlet on many of these valves has an S60x6 coarse buttress thread, which is about 60 mm, or 2.36 inches, across the outside of the threads.
But IBC fittings are not completely standardized. A fitting marked "2 inch" may use S60x6, NPT, NPS, BSP, or another thread. Some IBC tanks also have larger outlets. Measure your tank before buying an adapter.
The Most Common IBC Tank Fitting Size
For a typical plastic IBC tote used for rainwater storage, the bottom connection often looks like this:
| Part | Common size |
|---|---|
| Bottom valve | 2 inch / DN50 |
| Common outlet thread | S60x6 |
| S60x6 outside diameter | About 60 mm / 2.36 inches |
| S60x6 thread pitch | 6 mm |
| Common garden hose adapter outlet | 3/4-inch GHT |
| Common pump or plumbing adapter | 1-, 1 1/2-, or 2-inch pipe connection |
The S60x6 designation describes the thread rather than the opening through the valve. "S" refers to the coarse buttress-style thread, "60" refers to its approximate nominal diameter in millimeters, and "6" is the distance between thread peaks.
This distinction matters because a 2-inch valve does not necessarily accept an ordinary 2-inch plumbing fitting directly.
Why a 2-Inch Pipe Fitting May Not Fit
One of the easiest mistakes with an IBC tank is assuming that a valve described as "2 inch" has a standard 2-inch pipe thread.
It may not.
The 2-inch measurement often describes the valve's nominal flow size. The exposed connection may instead have a large, coarse IBC thread such as S60x6.
A standard 2-inch NPT pipe fitting has a very different thread pattern. NPT means National Pipe Taper, a common tapered pipe thread in North America.
S60x6 has much wider thread spacing.
Trying to force one onto the other can damage the plastic threads or leave you with a connection that leaks.
Instead, you normally use an IBC adapter that matches the valve on one side and provides the plumbing connection you need on the other.
For example:
S60x6 IBC valve → adapter → 3/4-inch garden hose
or:
S60x6 IBC valve → adapter → 1-inch pipe → pump
or:
S60x6 IBC valve → adapter → 2-inch camlock → transfer hose
A camlock, also called a cam-and-groove fitting, is a quick-connect fitting often used with pumps and larger water hoses.
How to Tell If Your IBC Has an S60x6 Fitting
Do not rely only on the tank's capacity. Two 275-gallon totes can have different valves.
Look at the threaded outlet after the shutoff valve.
Measure the outside diameter
Measure across the widest part of the male threads.
An S60x6 connection should be roughly 60 mm, or about 2.36 inches, across.
A caliper gives a much better measurement than a tape measure.
Look at the thread spacing
S60x6 threads are very coarse. There is about 6 mm between thread peaks.
If the threads look much finer, you may have a different connection even if the outside diameter is close to 60 mm.
Check the valve markings
Some valves have their size or thread molded into the plastic.
You may see markings such as:
- DN50
- S60x6
- 2"
- manufacturer or valve model information
The markings can help, but measure the fitting as well if you are replacing an adapter.
Other IBC Fitting Sizes Exist
S60x6 is very common, but it is not universal. Other IBC outlet arrangements include larger coarse threads and conventional pipe-thread connections. Examples reported on IBC equipment include S75x6, S80x6, S100x8, NPT, NPS, and BSP connections.
BSP means British Standard Pipe. It can look similar to some North American pipe threads, but BSP and NPT should not be treated as interchangeable.
Large IBC valves may also use a nominal 3-inch outlet rather than the more common 2-inch DN50 valve.
This is why buying an adapter simply labeled "IBC tote adapter" is risky. Check the connection listed on both sides of the adapter.
What Size Is the Top IBC Tank Opening?
The large top opening is separate from the bottom discharge fitting.
Many common IBC totes have a top fill opening around 6 inches or 150 mm. Some tanks use other lid sizes, including larger openings.
Do not assume the top lid size based on the bottom valve.
This matters if you want to add:
- a screened rainwater inlet
- an overflow arrangement
- a vent
- a level sensor
- a suction line
- a replacement lid
Measure the actual lid and thread before ordering parts.
What Adapter Do You Need for a Garden Hose?
If your IBC has the common S60x6 outlet, you can use an adapter that converts:
Look closely at common IBC connector thread dimensions to understand component compatibility before materials are finalized.
S60x6 female → 3/4-inch garden hose thread
Garden hose thread is often abbreviated GHT.
The adapter screws onto the IBC valve. A normal garden hose then attaches to the smaller connection.
Keep in mind that reducing a 2-inch valve to a 3/4-inch hose restricts flow. That may be fine for watering plants, filling buckets, or feeding a small gravity irrigation system.
It is less suitable when you want to empty the tank quickly or supply a high-flow pump.
What Size Should You Use for a Pump?
Match the plumbing to the pump rather than automatically reducing the IBC outlet to garden-hose size.
For example, if a transfer pump has a 1-inch suction connection, it often makes more sense to adapt the tote to suitable 1-inch plumbing instead of running through a long 3/4-inch garden hose first.
The important factors are:
- pump inlet size
- required flow rate
- hose or pipe length
- vertical lift
- restrictions from valves and fittings
Flow rate means how much water moves through the system over a given time, usually measured in gallons per minute.
Reducing the plumbing too early can restrict the pump. Follow the pump manufacturer's requirements for suction-pipe size and installation.
Never assume an IBC tank itself is designed to operate as a pressurized vessel. Most common IBC totes are intended for storage and gravity discharge, not for being pressurized by a water pump.
What Size Is Best for Rainwater Irrigation?
For simple rainwater irrigation, the best fitting size depends on what happens after the tank.
A garden hose or small drip system may eventually need a 3/4-inch or smaller line. But that does not mean the connection immediately leaving the tank should always be that small.
Keeping the main outlet larger can reduce flow restriction. You can then reduce the pipe closer to the irrigation equipment.
For example:
2-inch IBC outlet → adapter → larger main line → filter → pressure regulator if needed → drip tubing
A gravity-fed IBC has limited water pressure. Water pressure increases as the water surface gets higher above the outlet, but an elevated tote still produces much less pressure than a typical household water line.
Check the minimum pressure and flow requirements of filters, timers, valves, and irrigation equipment before connecting them.
Check the Gasket as Well as the Thread
A fitting can have the correct thread and still leak if the gasket is missing, damaged, or unsuitable.
IBC adapters often seal against a flat gasket rather than relying on the threads themselves.
Before installing an adapter:
- Clean dirt from the valve face and threads.
- Inspect the gasket for cracks, deformation, or damage.
- Seat the gasket correctly.
- Thread the adapter on straight.
- Tighten it enough to compress the seal without damaging the plastic.
Do not try to fix mismatched threads by adding large amounts of thread tape or sealant. If the fitting will not thread on normally, confirm its size and thread type.
Used IBC Tanks Need an Extra Check
If you are turning a used IBC tote into a rainwater tank, fitting size is not the only concern.
Find out what the container previously held.
A tote that carried an unknown chemical or unsuitable substance should not automatically be repurposed for garden water, household water, livestock water, or drinking-water storage just because it has been rinsed.
For drinking-water use in particular, the container, collection surface, plumbing, treatment system, maintenance plan, current laboratory testing, and applicable local requirements all matter.
The fitting size does not tell you whether the tank is suitable for potable water.
Measure Before Ordering an IBC Adapter
For most common IBC rainwater tanks, 2-inch DN50 with an S60x6 outlet is the first size to check. But treat it as a common configuration, not a guarantee.
Before ordering, identify:
- outside thread diameter
- thread pitch
- coarse or fine thread
- male or female connection
- connection you want on the other side
- hose, pipe, pump, or irrigation size
A few minutes spent measuring can prevent the common problem of buying a "2-inch IBC adapter" that is the right nominal size but the wrong thread.
Frequently Asked Questions
Are all IBC tote fittings 2 inches?
No. A 2-inch DN50 bottom valve is very common on standard IBC totes, but other valve and thread sizes exist. Always measure the fitting before buying an adapter.
What is the most common IBC tote thread?
S60x6 is one of the most common outlet threads. It is a coarse buttress thread with a nominal diameter of about 60 mm and a 6 mm thread pitch.
Is S60x6 the same as 2-inch NPT?
No. They are different thread systems. S60x6 is a coarse IBC buttress thread, while 2-inch NPT is a tapered pipe thread. An adapter is normally needed between them.
Can I connect a garden hose directly to an IBC tank?
Usually not unless the valve or existing adapter already has garden hose threads. A common setup uses an adapter from the IBC outlet, such as S60x6, to 3/4-inch garden hose thread.
How do I measure an IBC fitting?
Measure the outside diameter of the male threads, then measure the distance between thread peaks. Also check whether the thread is coarse or fine and look for molded markings on the valve.
What size IBC fitting should I use for a rainwater pump?
Match the downstream plumbing to the pump manufacturer's inlet requirements and needed flow. Avoid reducing a large tank outlet to a small hose before the pump unless the pump is designed for that arrangement.
Is the top opening the same size as the bottom IBC valve?
No. They are separate connections. Many common totes have a top fill opening around 6 inches or 150 mm, while the bottom discharge valve is commonly a 2-inch DN50 size.
