Understanding Fluidmaster 400 and 400A: A Comprehensive Comparison
The Fluidmaster 400 and 400A are both popular toilet fill valves, often causing confusion due to their similar names and appearances. While they share many similarities, there are distinct differences that might make one a better choice than the other for your specific needs. Let's dive into a detailed comparison to help you make an informed decision.
Fluidmaster 400: The Classic Choice
The Fluidmaster 400 has been a trusted name in toilet fill valves for decades. It's known for its durability, easy installation, and reliable performance. Here are some key features:
- Adjustable water level with a simple turn of the float arm.
- Performs well in both 3/8" and 7/16" supply lines.
- Comes with a 5-year warranty, reflecting its robust construction.
Fluidmaster 400A: The Upgraded Version
The Fluidmaster 400A is an upgraded version of the 400, incorporating modern features and improvements. Here's what sets it apart:

Fluidmaster 400 vs 400A: Key Differences
| Feature | Fluidmaster 400 | Fluidmaster 400A |
|---|---|---|
| Adjustable Water Level | Yes, with a float arm | Yes, with an easy-to-use dial |
| Supply Line Compatibility | 3/8" and 7/16" | 3/8" only |
| Warranty | 5 years | 7 years |
| Additional Features | None | Adjustable water level dial, 7-year warranty |
Which One Should You Choose?
The choice between the Fluidmaster 400 and 400A depends on your specific needs:
- If you need compatibility with both 3/8" and 7/16" supply lines, choose the 400.
- If you prefer the convenience of an adjustable water level dial and a longer warranty, opt for the 400A.
Both models are excellent choices for their respective use cases, offering a blend of durability, reliability, and easy installation. By understanding the subtle differences between the Fluidmaster 400 and 400A, you can make an informed decision that best suits your requirements.