Shower Thermostatic Cartridges
Thermostatic shower cartridges for concealed and exposed valves, covering most UK brands. Each replacement is selected for the body length, spline pattern and seal arrangement of the original valve, so the trim and pipework stay where they are.
Please note: all our thermostatic cartridges arrive in a sealed see-through wrapper. The wrapper, and the delivery note, both state that the seal voids the return. Cartridges are non-refundable once the wrapper has been opened.
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Cartridges for Thermostatic Shower Valves
Replacing the Cartridge, Not the Whole Shower Valve
Shower running hot then cold. Drips at the head when the valve is off. A temperature dial that spins without doing much. These are cartridge faults, almost every time, and the cartridge is the part that comes out and gets replaced.
The valve body stays in the wall. Replacing the thermostatic cartridge fixes the fault without disturbing the trim plate, the pipework, or the tiles around it. A new cartridge runs a fraction of a whole-valve replacement, with no plumber rip-out and no retiling. That is the reason this category exists, and the reason it is the right place to start.
Cartridges for Concealed and Exposed Thermostatic Shower Valves
Two valve formats take different cartridges. Confirm yours before ordering.
Concealed valves
Pipework's inside the wall. Trim plate and dials are all you see on the bathroom side. Behind the plate sits the cartridge, and once the trim is removed it pulls straight out for replacement. Standard fit on most newer shower installations.
Exposed valves
Valve body fixed to the wall surface, often a chrome bar valve with the cartridge inside one end. Pipes run to either side. Standard on bar shower mixers and traditional installations.
Plate flush against the tilework, no pipework on show, that is a concealed shower cartridge job. Chrome body fixed to the wall with pipes running to it, that is exposed.
Replacement Cartridges Sized for Mira, Bristan, Triton and Other Major UK Brands
Two cartridges can look identical online and fit completely different valves. The part has to match the original on body diameter, body length, spline count, O-ring layout and inlet type, every one of them. One spec wrong, the part comes back unused.
The cartridges in this range cover brass and plastic bodies, three-O-ring layouts at the standard count, twenty and twenty-four spline spindles, and both push-in and screw-in inlets. Body diameters cluster around 32mm and 33mm. Lengths run from roughly 80mm up to 120mm and longer for deep-mounted units. Brand fitments include Bristan, Vado, Crosswater, Mira, Aqualisa, Ideal Standard, Grohe, Hansgrohe, Triton and a wide list beyond. The fastest way to confirm yours: pull the existing cartridge, measure the body, count the splines, and check the trim plate or valve body for a brand mark. If it is not obvious, photograph the cartridge and the trim side by side and the team will identify it.
Frequently Asked Questions About Thermostatic Shower Cartridges
How do you know if a shower cartridge needs replacing?
The shower runs hot then cold during use, drips at the head when the valve is fully off, drifts off the dialled temperature, fails to reach a usable temperature, or stops responding to the temperature control. Limescale buildup inside the cartridge and worn rubber seals are the main causes. If the valve body shows no leaks at the wall and pipework is dry, the fault is inside the cartridge and replacement is the fix.
Is a thermostatic cartridge the same as a mixer cartridge?
No. A thermostatic cartridge holds a set temperature using an internal wax or bimetallic element that reacts to pressure and temperature changes in the supply. A standard mixer cartridge blends hot and cold by hand without temperature regulation, so the output drifts when the supply changes. Thermostatic shower mixer valves use a thermostatic cartridge, not a manual mixer cartridge, and the two are not interchangeable inside the same valve body.
How do I identify which thermostatic cartridge fits my valve?
Pull the existing cartridge from the valve body. Measure the body diameter (32mm and 33mm cover most of the range), measure the body length (between 80mm and 120mm for the bulk of cartridges), count the splines on the spindle (20-spline and 24-spline are the dominant patterns), and check for a brand mark on the trim plate or valve body. The inlet style (push-in or screw-in) confirms the connection type. If the cartridge is unmarked or unclear, photograph it alongside the trim plate and the team will identify it.
Will a cartridge from one brand fit another brand's valve?
Sometimes. Brand-original cartridges are designed to a specific valve body, but several aftermarket cartridges are produced as universal-fit replacements that physically match multiple brands when the body diameter, length, splines and inlet style line up. The match is mechanical, not branded. A 32mm brass cartridge with 20 splines and push-in inlets will fit any valve body machined to those same dimensions, regardless of the badge on the trim plate. Always confirm the body size, spline count and inlet style before assuming cross-fit.
What does this category cover, and what does it not cover?
This category covers replacement thermostatic cartridges that fit inside concealed and exposed thermostatic shower valves, across most UK brands including Bristan, Vado, Crosswater, Mira, Aqualisa, Ideal Standard, Grohe and Triton. It does not cover the valve body itself, diverter cartridges that switch flow between outlets, flow valves and shut-off cartridges, shower handles or levers, or non-thermostatic mixer cartridges. Each of those sits under Shower Valve Spares as its own category.