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When should a shower cartridge be replaced?

A shower cartridge is the replaceable part inside many mixer showers, and a drip or a stiff handle is a reason to ask a plumber rather than to guess the part. This page says what to tell them, and it does not set out a way to take the valve apart.

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By the QuoteZila editorial team. Editorial policy.

What are people usually trying to stop?

A mixer shower that drips after the handle is shut, or a handle that will no longer turn smoothly, is often described as a cartridge fault. The cartridge is the part inside the valve. It is not the hose, the head, or the rail. If water is coming from the hose joint, say that, because a washer at the hose is a smaller job than a new cartridge. If water is staining the ceiling of the room below, say that too, because the leak may be the tray or a pipe, not the valve.

QuoteZila is starting in Cheshire. Crewe, Nantwich and Sandbach are among the first places people can post. Anyone in the UK can post a job or register.

Why is the model number the whole job?

Cartridges are made to fit a particular valve. A photo of the handle is not a part number. Look for a brand plate on the valve body if you can see it without taking anything apart, and write down any code printed there. If you cannot see a code, say so. A plumber who has the valve in front of them can order the matching part. Buying three near-matches and hoping is how a small drip becomes a scarred thread.

This page does not tell you to shut the water, lift the handle, or undo the valve. Those steps are easy to describe and easy to get wrong on a thermostatic mixer, where the temperature stop is part of the same assembly. Hand the identification to the person who will fit the part.

Where does a plumber look the job up?

WaterSafe describes its register as a free online directory of approved plumbers and other water specialists, searchable by postcode, and says approved contractors issue certificates of compliance [S1]. QuoteZila does not look anyone up on that register for you. If you want a plumber who can issue that certificate, search it yourself and ask the person who quotes whether they are on it.

Citizens Advice says some traders charge for quotes, so ask first, and to get the price in writing from at least 3 traders [S2]. A quote is a fixed price and an estimate is a rough guess [S2]. A business registers for VAT when taxable turnover for the last 12 months goes over £90,000, or is expected to in the next 30 days [S3]. A cartridge visit is often a small invoice. Ask whether VAT is included anyway.

When is it no longer a cartridge?

The Planning Portal says installing a new kitchen or bathroom where there was not one before is likely to need building regulations approval, while a refit of units and fittings generally does not, except where drainage or electrical work inside the refit needs it [S4]. Tell the plumber if you are only changing the cartridge, or if you also want the valve moved, a new supply, or a different shower position. Those are different approvals.

If the unit is an electric shower rather than a mixer fed by hot and cold pipes, stop. The Planning Portal says electrical installation work in a home must comply with the building regulations, and that certain riskier jobs are notifiable, including a new circuit [S5]. In England, the spaces around baths and showers are special locations [S5]. An installer registered with a competent person scheme can self-certify [S5]. This page does not tell you to open an electric shower.

Electrical Safety First: find a registered electrician; NICEIC; NAPIT. QuoteZila is not affiliated with this organisation.

Jobs you might post

These are examples, not taken from real job posts.

  • Mixer shower over a bath, drip from the valve when the handle is off. Brand and any model code in the post, plus a photo of the valve face. Ask for a written price that includes the matching cartridge if they supply it.
  • Thermostatic mixer in an enclosure, handle stiff, temperature still steady. Say you do not want the valve moved.
  • Electric shower that has failed. Say it is electric, and ask for an electrician rather than a cartridge guess.

Anyone in the UK can post or register. QuoteZila is a new, early-stage project, so how many plumbers reply depends on who has joined near you [QZ5]. Up to five matched local businesses can quote [QZ2]. QuoteZila is free for customers and local businesses [QZ1].

Questions about shower cartridges

What is a shower cartridge?

It is the part inside many mixer shower valves that the handle operates, so the flow and the mix can be controlled. Brands do not share one shape. The useful step is to note the maker and the model on the valve, or to ask a plumber to identify it, rather than to buy a cartridge that only looks similar.

Does replacing a cartridge need building regulations approval?

The Planning Portal says a bathroom refit with new units and fittings does not generally need building regulations approval, although drainage or electrical work within that refit may. Swapping a cartridge in an existing mixer is not the same as creating a bathroom where there was not one before, which that page says is likely to need approval.

What if the shower is electric?

An electric shower is a different appliance from a mixer on the hot and cold pipes. The Planning Portal says electrical work in a home must comply with the building regulations, and that in England the spaces around baths and showers are special locations. A new circuit is notifiable. Use a registered electrician for that unit. This page does not describe opening it.

Does QuoteZila check plumbers?

No. We don't check insurance, qualifications or registrations, so please check these yourself before you hire. You can report a quote or a business from your job page.

Honest status: QuoteZila is new. We're starting in Cheshire, beginning with Crewe, Nantwich and Sandbach, and growing area by area. Anyone in the UK can still post a job or register a business. How fast you get quotes depends on how many local businesses have joined near you. Businesses can register and receive jobs straight away. We don't check insurance, qualifications or registrations, so please check these yourself before you hire.

For an electric shower, use the Electrical Safety First register search.

This page is general information, not professional or legal advice. QuoteZila does not check Gas Safe, WaterSafe, NFRC, NICEIC or other registrations against the register on your behalf: look them up yourself.

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Plumbers cover mixer valves. Electricians cover an electric shower. The plumber cost guide is about comparing plumbing quotes more generally. A tap cartridge is a different part: changing a tap cartridge. All services.

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Sources

  1. QZ1: QuoteZila product fact. QuoteZila pricing line.
  2. QZ2: QuoteZila product fact. QuoteZila FAQ.
  3. QZ5: QuoteZila product fact. QuoteZila home callout.
  4. S1: WaterSafe Register, WaterSafe. Accessed 2026-10-28. https://www.watersafe.org.uk/
  5. S2: Before you get work done on your home, Citizens Advice. Accessed 2026-10-28. https://www.citizensadvice.org.uk/consumer/getting-home-improvements-done/before-you-get-building-work-done/
  6. S3: When to register for VAT, GOV.UK. Accessed 2026-10-28. https://www.gov.uk/register-for-vat
  7. S4: Is building regulations approval needed for work to a kitchen or bathroom?, Planning Portal. Accessed 2026-10-28. https://www.planningportal.co.uk/permission/common-projects/kitchens-and-bathrooms/is-building-regulations-approval-needed-for-work-to-a-kitchen-or-bathroom/
  8. S5: Building Regulations: general information, electrics, Planning Portal. Accessed 2026-10-28. https://www.planningportal.co.uk/permission/common-projects/electrics/building-regulations-general-information/