What you need to do before you start

Replacing shower taps is a job most homeowners can do in an afternoon with basic tools. The work involves disconnecting the old tap body from the pipes behind your wall, removing the cartridge or valve inside, and installing a new one. You do not need to be a plumber — the hardest part is usually getting the old tap off, not putting the new one on.

Before you touch anything, turn off the water supply to your shower. Look under your sink or in your basement for the main shut-off valve, or find the isolation valve specific to your shower line if one exists. Turn it clockwise until it stops. Then turn on the shower to release any pressure still in the pipes. If water keeps running, you have not shut off the right valve — keep looking.

Gather your tools now: an adjustable wrench, a screwdriver (both Phillips and flat-head), a hex key set, plumber's tape, and a bucket to catch drips. You will also need the replacement tap cartridge or valve that matches your current tap brand — this is not something you can guess at. Take a photo of your existing tap or bring the old cartridge to the hardware store to match it exactly.

Key Takeaways

  • Turn off the water supply and release pressure by running the shower before you disconnect anything.
  • The cartridge or valve inside your tap is the part that wears out; you often replace only that piece, not the entire tap body.
  • Tap brands are not interchangeable — a Moen cartridge will not fit a Kohler tap, so match the brand before you buy.
  • If the old tap is stuck, apply penetrating oil and wait 15 minutes rather than forcing it, which can crack the pipe fitting behind the wall.
  • Wrap new threads with plumber's tape before reconnecting to prevent leaks at the connection points.

Identify your tap type and find the cartridge

Most modern shower taps have a removable cartridge or valve inside — that is the part that fails and needs replacing. Older taps sometimes have separate hot and cold valves, which is a different job. Look at your tap handle: if there is one handle that moves up and down or side to side, you have a single-cartridge tap. If there are two separate handles, you may have a two-valve setup.

For a single-handle tap, the cartridge is usually hidden behind a decorative cap or plug. Look for a small slot or notch on the handle itself, or a cap at the base of the handle. Pry it gently with a flat-head screwdriver — it will pop off. Underneath you will see a screw holding the handle on. Remove that screw and pull the handle straight out. Behind it is a trim ring or escutcheon (the decorative ring against the wall), which you may need to unscrew or pry off to access the cartridge body itself.

Write down the brand name you see on the tap — Moen, Kohler, Delta, Pfister, and Grohe are common ones. The cartridge you buy must match this brand. If you cannot read the name, take a photo and show it to someone at the hardware store, or remove the old cartridge and bring it with you.

Remove the old cartridge or valve

Once you have exposed the cartridge, you will see it is held in place by a large nut or retaining clip. This nut is usually brass or plastic and sits right where the cartridge enters the tap body. Use your adjustable wrench to turn this nut counterclockwise — it will be tight, so apply steady pressure rather than jerking it. If it will not budge after a few tries, spray it with penetrating oil (like WD-40), wait 15 minutes, and try again.

Once the nut is loose, you can unscrew it by hand. Pull the cartridge straight out of the tap body. It will likely have water in it, so hold it over your bucket. You may see a small clip or pin holding the cartridge in place — remove that first if present.

Before you install the new cartridge, clean the inside of the tap body with a dry cloth. Remove any mineral buildup or debris. If the tap has been leaking, there may be sediment inside — wipe it out. This step prevents the new cartridge from getting stuck or wearing prematurely.

Install the new cartridge and reassemble

Check the new cartridge against the old one to confirm they are identical. The shape, size, and any grooves or notches must match. If they do not, you have the wrong cartridge — do not force it in.

Insert the new cartridge into the tap body, pushing it straight in until it seats fully. You should feel it click or bottom out. If it does not go in smoothly, stop and check the orientation — cartridges only fit one way. Some cartridges have a flat edge or a notch that aligns with a slot in the tap body. Rotate the cartridge slightly if needed until it slides in.

Once the cartridge is seated, screw the retaining nut back on by hand first, then tighten it with your wrench. Do not over-tighten — snug is enough. Reinstall the trim ring or escutcheon, then the handle, and finally the decorative cap. Make sure the handle points in the direction you expect (usually straight down for off, up for on).

Reconnect the water supply and test for leaks

Before you turn the water back on, check the connections where the tap pipes enter the wall. If you had to disconnect any fittings to remove the old tap, wrap the new threads with plumber's tape (also called PTFE tape or Teflon tape). Wrap it clockwise around the threads three to four times, then reconnect the fitting and tighten it with your wrench.

Turn the main water shut-off valve back on slowly. Listen for any hissing or spraying. Turn on the shower and let it run for a minute. Check behind the tap and under the sink for drips. If water is leaking from the connection points (not from the tap spout itself), turn the water back off and tighten the fitting a quarter turn more. If water is leaking from inside the tap where the cartridge sits, the cartridge may not be seated correctly — you may need to remove and reinstall it.

Once the water is running cleanly and there are no leaks, test the hot and cold water. The handle should move smoothly, and the temperature should change as you move it. If the hot and cold are reversed, you can usually rotate the cartridge 180 degrees to swap them — turn off the water, remove the handle and retaining nut, rotate the cartridge, and reassemble.

What to do if the old tap is stuck or corroded

If the retaining nut will not turn even after applying penetrating oil, do not force it. Forcing can crack the fitting behind the wall, which means cutting into the wall to repair it. Instead, apply penetrating oil again and wait an hour. Tap the nut gently with a hammer to help the oil work into the corrosion, then try again.

If the cartridge itself is stuck inside the tap body, you may need a cartridge puller — a specialized tool that grips the cartridge and pulls it straight out. These are inexpensive and available at most hardware stores. Rent one if you do not want to buy it. Do not try to pry the cartridge out with a screwdriver, as this can damage the tap body.

If you have an older two-handle tap with separate hot and cold valves, the job is more complex because each valve may have a different design. In that case, it is worth having a plumber handle it, or research your specific tap model online to find detailed instructions for your brand.

Common mistakes that cause leaks or damage

The most common mistake is buying the wrong cartridge. Tap brands are not interchangeable — a Moen cartridge will not fit a Delta tap, and forcing it will damage both the cartridge and the tap body. Always confirm the brand before you buy, and if you are unsure, bring the old cartridge with you to the store.

Another mistake is over-tightening the retaining nut. This can compress the cartridge seal and cause leaks, or crack the nut itself. Tighten until snug, then stop. If it still leaks after that, the cartridge itself may be defective — return it and try a new one.

Forgetting to use plumber's tape on threaded connections is a common source of slow leaks that appear days later. If you disconnected any fittings, wrap the threads before reconnecting. This is cheap insurance against a leak that will damage your wall.

Frequently Asked Questions

Can I replace just the cartridge, or do I have to replace the whole tap?

In most cases you replace only the cartridge, which is the internal part that wears out. The tap body, spout, and handle usually last much longer. If the cartridge is available separately for your brand, that is all you need to buy. If your tap is very old or the body is cracked, you may need to replace the entire tap assembly.

What if I turn the water back on and it still leaks from the same spot?

If water leaks from the connection where the tap enters the wall, turn the water off and tighten that fitting another quarter turn. If it leaks from inside the tap body where the cartridge sits, the cartridge may not be fully seated — remove the retaining nut, pull the cartridge out, and reinstall it, making sure it goes in straight and clicks into place.

How do I know which way the handle should point?

Most taps have the handle pointing down when the water is off, and you push it up to turn the water on. If yours is reversed after installation, turn off the water, remove the handle and retaining nut, rotate the cartridge 180 degrees, and reassemble. The handle will then point the way you expect.

Do I need to drain the pipes before I start?

You do not need to drain the entire house, but you should turn off the water supply and run the shower to release pressure. This prevents water from spraying when you disconnect the cartridge. Have a bucket ready anyway — there will be some water in the tap body.

What if the new cartridge leaks right away?

Check that it is fully seated and the retaining nut is snug but not over-tightened. If it still leaks, the cartridge may be defective. Return it to the store and ask for a replacement. Bring your receipt and the old cartridge to confirm you bought the right part.