How to Change a Washer on a Mixer Tap
A dripping mixer tap isn’t just annoying — it can waste litres of water a day and drive up your bill. In many cases, the culprit is a worn washer, which is a simple and inexpensive part to replace. With the right tools and a little care, you can change it yourself.
At Pleasant Plumbers, we help homeowners and landlords across London repair and upgrade kitchen and bathroom taps efficiently. Here’s a step-by-step guide to replacing a washer on a standard mixer tap — plus when it’s best to call in the pros.
Tools & Materials You’ll Need
- Adjustable spanner or basin wrench
- Flathead screwdriver
- Replacement washer (usually 3/8" or 1/2", but check your tap type)
- Cloth or towel
- Tap reseating tool (optional if seat is damaged)
Step-by-Step: How to Change the Washer
Step 1: Turn Off the Water Supply
Locate and turn off the isolation valves under the sink. If you don’t have these, shut off the water at the main stopcock.
Turn on the tap to drain any remaining water.
Step 2: Plug the Sink
Pop the plug into the sink to prevent losing any small parts down the drain.
Step 3: Remove the Tap Handle
Use a flathead screwdriver to gently pry off the tap cap (usually on the top of the handle) to expose the screw.
Unscrew it and carefully lift off the handle.
Step 4: Unscrew the Tap Bonnet
Using a spanner or tap wrench, loosen and remove the brass bonnet nut beneath the handle.
This will reveal the valve mechanism — also known as the tap spindle or cartridge
Step 5: Remove the Old Washer
At the base of the valve, you’ll see a small rubber washer held in place with a screw or clip. Remove it and replace with a new washer of the same size and shape.
If the valve seat (inside the tap body) looks worn or uneven, use a tap reseating tool to restore a smooth surface.
Step 6: Reassemble the Tap
Reinsert the valve, tighten the bonnet nut, and refit the tap handle and screw.
Restore the decorative cap.
Step 7: Turn the Water Back On and Test
Turn on the isolation valves or main stopcock. Open the tap slowly to check for leaks or drips.
If the tap still drips, the washer may not be seating properly — or the valve seat may be too worn.
When to Call a Plumber
You may need professional help if:
- The tap is seized or corroded
- The valve seat is badly worn
- Your mixer tap has ceramic disc cartridges (these require a different process and parts)
- You’ve changed the washer and the tap still leaks
At Pleasant Plumbers, we can diagnose issues quickly and ensure a long-term fix — whether you need a repair or a full tap replacement.
Need Help With a Leaky Mixer Tap?
We provide fast, affordable tap repairs across London and can advise on whether to replace washers, cartridges, or the whole unit.
📲 Call or WhatsApp 0800 046 1000
📧 Email [email protected]
🌐 Visit pleasantplumbers.com
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