How to Remove and Replace the Internal Cartridge of a Single-Lever Mixer Tap (by Capitan Farloc)

If your single-lever mixer tap is leaking or acting up, it’s probably time to replace the inner cartridge. No worries — this guide will walk you through each step to take the tap apart and swap the cartridge without any hassle. You’ll just need a few simple tools like an adjustable wrench, a screwdriver, and a bit of patience. Just remember to turn off the water before you start and be careful not to damage any delicate parts. Ready to roll up your sleeves? Let’s get started!

What Is a Single-Lever Mixer Tap?

Unlike traditional taps, single-lever mixer taps do not use rubber seals for water-tightness. Instead, they rely on a ceramic disc system, which ensures greater durability and requires minimal force to operate.
This system is typically enclosed in a cylindrical plastic housing and is commonly referred to as the mixer cartridge.
When a tap stops functioning properly, the usual solution is simply to replace the cartridge.
This article explains how to remove the cartridge from the tap in order to replace it.

STEP 1 - Removing the Mixer Lever

Let’s go step by step. The first thing to do is, of course, turn off the water supply—either using the main bathroom shut-off valve or, if available, the two valves under the sink.
Next, proceed to remove the single-lever handle. This is usually secured with a screw, which can be accessed by:

• Fully lifting the lever (as shown in the picture).
• Removing a small plastic cap on the front (typically half blue and half red).
• Unscrewing or pulling off the decorative cover on top of the lever, which may be threaded or snap-fit.

However, even after loosening the locking screw, the lever may still stick to the spindle. In this case, patience is key—gently apply leverage:

• Left and right,
• Forward and backward, until the piece comes loose.

STEP 2 - Removing the Chrome Cover

After removing the lever, you will see a chrome-plated cover with a central hole, through which the square spindle that holds the lever protrudes.
This component, typically made of plastic or metal, must be unscrewed to remove it and access the cartridge.
Sometimes, unscrewing it can be tricky, as dust and limescale deposits from water can accumulate in the threading, making it difficult to loosen.
If the cover does not unscrew easily, try using a descaling and release spray. These sprays are available from hardware stores and DIY shops, and can be conveniently applied using a thin nozzle, even through the top hole.

Even with the use of a release oil, removing the semi-spherical chrome cover can be tricky, mainly because it’s difficult to firmly grip a piece with that shape.
A useful tool for this task is a rubber strap wrench (as shown in the image), typically used for removing car oil filters.
Alternatively, if you have a standard metal band filter wrench, you can increase grip and prevent scratches by placing a rubber strip (such as a piece cut from an old bicycle inner tube) between the metal band and the chrome cover before loosening it.

STEP 3 - Removing the Locking Ring

At this stage, you will find a system securing the cartridge in its housing.
In the tap shown in the picture, this function is performed by a threaded locking ring with four tabs, which are designed to be unscrewed using a special key.
However, since very few DIY enthusiasts will have such a key, an alternative method must be used to loosen the ring. I usually rely on one or two screwdrivers in the following ways:

1. Single-screwdriver method: Place a flathead screwdriver against one of the tabs (as shown in the picture). Then, gently tap the handle with a rubber hammer to loosen the ring.
2. Dual-screwdriver method: Position two screwdrivers vertically against two opposite tabs, holding their handles with one hand. With the other hand, insert the rubber hammer handle between the screwdriver shafts as low as possible, and use it as a lever to rotate the ring counterclockwise to unscrew it.

The first method is more effective for breaking the seal but should be used with caution, as excessive force could damage the ring. The second method works best when the ring is difficult to loosen but isn’t completely stuck.

After unscrewing the locking ring or otherwise removing the cartridge securing system (as designs may vary across different tap brands), you will finally see the problematic component—the cartridge, now fully detached.

STEP 4 - Removing the Old Cartridge

The mixer cartridge should be extracted carefully, as there is a rubber seal underneath that may have partially adhered to the housing.
If this happens, it’s important to detach it gently, as not all manufacturers include a replacement seal with the cartridge. If the seal breaks, it could create a problem during reassembly.

STEP 5 - Replacing and Reinstalling the New Cartridge

The image shows how the cartridge and its seal appear after removal.
Since there is no universal design standard for these cartridges, it’s highly recommended to bring the original part as a sample when searching for a replacement.
If you need to reuse the old seal, it should be carefully cleaned to remove any limescale deposits.
Before reinstalling, lubricate the seal with a thin layer of food-grade petroleum jelly or, if unavailable, apply a drop of olive or seed oil to help it stay correctly positioned in its seat.

Before reinstalling the new cartridge, it’s good practice to thoroughly clean the inside of the tap, particularly the thread where the locking nut will be screwed on.
Applying a light layer of food-grade petroleum jelly or oil to the thread using a finger will help ensure smooth assembly and prevent future sticking.

...And What If You Can’t Find a Replacement Cartridge?

If, upon external inspection, the cartridge shows no mechanical damage but a replacement for your tap is unavailable, you could try servicing the existing one.
It’s not always possible to restore an old cartridge, but if addressed in time and properly serviced, it could last for years.
If you're interested in this process and want to learn more, simply visit the article dedicated to it:
How to Service and Repair the Internal Cartridge of a Single-Lever Mixer Tap (by Capitan Farloc)

Thank you all!
Luciano (Capitan Farloc)