Cartridge Retaining Nut
Tap cartridge retaining nuts, retention nuts, cartridge locking nuts and cartridge nuts for mixer taps and shower valves. The retaining nut is the threaded brass collar that screws into the tap body and holds the cartridge firmly in position. Without it seated correctly, the cartridge shifts under pressure and the tap drips. We stock branded and generic sizes not widely available at trade counters.
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Tap and Shower Cartridge Retaining Nuts for Mixer Taps and Shower Valves
What the retaining nut does, when it fails, and which sizes are covered here.
The cartridge retaining nut screws into the tap body and clamps the cartridge in place. On mixer taps it is typically a brass collar with an external thread — you unscrew it to remove the cartridge, fit the replacement, then torque the nut back down. On shower valves the same principle applies, though the nut profile and thread pitch vary by brand and model. The nut takes repeated stress. Threads wear, brass corrodes in hard water areas, and over-tightening during a previous cartridge change can strip the thread entirely. In each case the fix is a replacement retaining nut. We stock 30mm, 32mm and further sizes covering Bristan, Crosswater and Chartley Stone models not available through standard trade counters.
Retaining Nut, Retention Nut, Cartridge Nut, Locking Nut: Which Term Describes Your Part?
The same part goes by several names depending on the brand and who fitted the tap originally.
Questions About Cartridge Retaining Nuts
Identification, sizing, and fitting questions answered for tap and shower valve retaining nuts.
How do I know if the cartridge retaining nut is the part that needs replacing?
If the cartridge moves or rocks slightly when the tap handle is operated, the retaining nut has either loosened or its thread has failed. A tap that drips immediately after a cartridge change, despite the new cartridge being correct, usually points to a stripped or cross-threaded retaining nut that is no longer clamping properly. Remove the nut and inspect the thread. If it turns without resistance or the brass is visibly damaged, replace it.
What size cartridge retaining nut do I need?
The most common sizes for mixer tap retaining nuts are 30mm and 32mm across the thread diameter, though shower valve nuts vary more widely by brand. The safest approach is to remove the existing nut and measure the outer thread diameter directly. Do not rely on the cartridge size alone, as the nut diameter is not always the same as the cartridge diameter. If you are unsure, email us a photo of the existing nut alongside a ruler and we will identify the correct replacement.
Is a cartridge retaining nut the same as a retaining clip?
No. A retaining nut threads into the tap body using a screw thread and requires a tap spanner or cartridge wrench to remove. A retaining clip is a sprung circlip or horseshoe clip that slots into a groove and is removed by hand or with a flat-blade screwdriver. Some cartridges use one method, some the other. Check whether your cartridge has a threaded collar around it or a clip sitting in a groove before ordering either part.
Will a retaining nut from a different brand fit my tap?
Only if the thread diameter and pitch match exactly. Retaining nuts are not universal. A 30mm brass nut from one brand will fit any tap body with a matching 30mm thread, regardless of brand, but thread pitch differences between European and UK-spec taps can mean two nuts of the same outer diameter will not interchange. Always match the thread diameter and pitch from the old nut, not just the outer diameter. When in doubt, bring the old nut to compare before ordering.
Can I replace the retaining nut without replacing the cartridge at the same time?
Yes, if the cartridge itself is in good condition. Remove the nut, check the cartridge for cracking, scoring or worn ceramic surfaces, then refit the cartridge with the new nut and tighten to hand-tight plus a quarter turn. Do not over-torque. If the tap was dripping before you started, it is worth inspecting the cartridge while it is out. For mixer tap cartridges see our Mixer Tap Cartridges and for ceramic disc taps see Tap Ceramic Disc Cartridges.
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