4mm Airline Tee - Splits One Airline into Two
Best for: anyone running more than one airstone off a single air pump and needing to split the airline.
Our thoughts
It's about as basic a part as you'll find in a hydro setup, but it's the kind of thing you don't want to be without when you're trying to add a second airstone at 11pm. Cheap enough to keep a couple spare. Gets the job done properly.
The 4mm Airline Tee is a simple T-shaped connector that splits a single 4mm airline into two, letting you run an extra airstone from the same air pump rather than needing a second pump. It fits standard 4mm internal diameter airline tubing, the size used by common air pumps such as those in the Charles Austen ET range.
How it compares
This is a commodity fitting - the only real choice is between a basic tee like this and a multi-outlet air manifold if you need to split into several lines rather than just two.
- A tee is the simplest way to add a second airline from one pump; a manifold with individual valves makes more sense once you're running three or more airstones and want to control each one
- Works with standard 4mm airline used across most budget and mid-range air pumps, not tied to one specific brand
For splitting one line into two, there's no need to overcomplicate it - this does the job.
Usage guidance
Fitting
Push 4mm airline firmly onto each of the tee's three barbed outlets until fully seated.
Balancing airflow
Expect airflow to split roughly evenly between both lines - if you need to favour one airstone over another, an inline valve on one branch gives you that control.
Checking for leaks
Run the pump briefly after fitting and check each joint for air escaping around the tubing before leaving it running unattended.
Technical specifications
- Vendor: Charles Austen
- Tubing size: 4mm internal diameter airline
- Outlets: 3 (1 inlet, 2 outlets)
- Use case: splitting one airline into two for an extra airstone
Who this is for
- Growers adding a second airstone to a reservoir without buying a second air pump
- Anyone running Charles Austen or similar 4mm airline air pumps
- Growers who want a cheap spare on hand for when a fitting fails
Our take
Not much to say about a part this simple - it splits your airline cleanly and doesn't fail. Worth grabbing a couple while you're ordering other bits, since it's exactly the kind of small part that's annoying to be without.
Does exactly what it should, day in, day out.
