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Tap Valves : Clockwise and Anti-Clockwise explained

Tap Valves : Clockwise and Anti-Clockwise explained

This guide explains how to tell whether your tap uses a clockwise (CO) or anti-clockwise (ACO) opening valve. This is essential when replacing ceramic disc valves in modern kitchen taps, especially lever-style taps where the direction the handle turns determines the type of valve needed.

1. Types of Tap Valves

There are two main types of valves used in kitchen taps:

Compression Valves (Twist Turn Handles)

• Found in older taps
• Handles twist several times to open and close
• Both hot and cold valves usually turn anti-clockwise to open
• These valves are usually interchangeable i.e the exact same valve goes into hot or cold side.

Ceramic Disc Valves (Quarter Turn)

• Used in most modern lever taps
• Open and close with just a 90° turn
• ‘Cold’ valve opens anti-clockwise (ACO)
• ‘Hot’ valve opens clockwise (CO)
• Not interchangeable

More detail here: Different Valves used in Kitchen Taps

2. How to Tell Which Valve You Need

Don’t assume based on which side of the tap is hot or cold. The most reliable method is to observe which direction the handle turns to open the water:

If the handle turns clockwise to open, you need a CO valve (clockwise opening).
If the handle turns anti-clockwise to open, you need an ACO valve (anti-clockwise opening).

Even if you’re replacing the valve in the same location (left or right), the direction the lever moves is what matters.

For example, in a standard setup:

• Right-hand lever turns anti-clockwise to open: needs ACO (cold) valve
• Left-hand lever turns clockwise to open: needs CO (hot) valve

3. What If the Tap Has Been Plumbed the Wrong Way Round?

In most UK installations, hot water is connected to the left-hand side and cold water to the right-hand side of the tap.

However, if the tap was plumbed incorrectly — for example, hot water to the right and cold water to the left — then the side of the tap won’t match the valve type.

This is why you should always go by the direction the handle turns, not by whether the tap is on the left or right.

Handle direction tells you the valve type:

• Turns clockwise to open = CO (clockwise opening valve)
• Turns anti-clockwise to open = ACO (anti-clockwise opening valve)

4. Common Tap Examples

Standard Two Lever Tap

• Levers pull toward the body to turn water on
• Hot side is on the left, cold on the right (when plumbed correctly)
• You’ll need:
  • ACO valve for cold (turns anti-clockwise)
  • CO valve for hot (turns clockwise)

Bridge Lever Tap (Levers Start Horizontal)

• Levers are horizontal in the off position
• Both levers turn inward to switch on
• Requires:
  • CO valve on the right (opens clockwise)
  • ACO valve on the left (opens anti-clockwise)

5. Special Case Taps

Two Lever Filterflow / Aquifier Taps

• Hot side has a standard valve
• Cold side uses a diverter cartridge to control cold and filtered cold

Triflow Taps (3-Valve Taps)

• Have valves for hot, mains cold, and filtered cold
• Mains and filtered cold valves are often identical

How to identify which valve is dripping:

1. Run the hot water and turn it off
2. If the drip stays hot, it’s likely the hot valve
3. If the drip turns cold, it’s likely one of the cold valves

Tip: If unsure which cold valve is faulty, you may need to test a new valve in both positions. Fitted valves cannot be returned.

Other useful guides

Why Is My Tap Dripping? Common Causes and How to Identify the Problem

Need Help Replacing a Valve?

Check out this easy guide:
7 Easy Steps to Replace a Kitchen Tap Valve