Stems & CartridgesThe faucet valve parts index

Guide

How to measure a faucet stem or cartridge

Five numbers identify almost any stem or cartridge: brand, length, broach, type and, for ceramic cartridges, diameter. You need a ruler or tape measure, a piece of masking tape, and the old part in your hand.

Before you start

  1. Shut off the water to the fixture. For a shower with no integral stops, that usually means the main shutoff.
  2. Remove the handle, then the bonnet nut or retaining clip, and pull the stem or cartridge straight out. Some cartridges need a puller tool.
  3. Lay the part on a towel next to the sink so nothing small rolls down the drain.

1. Brand and any numbers on the part

Look at the handle, escutcheon and spout for a brand name, then check the part itself for stamped or molded numbers. A number on the part is the fastest route: search it. Many stems carry no number at all, which is what the next steps are for.

2. Overall length

Measure end to end, from the tip of the broach (the splined end the handle fits on) to the very bottom. Write it down in inches to the nearest sixteenth. If the stem has a rubber washer and screw on the bottom, note whether you measured with it in place: if your number is close to a listing but not exact, the washer is usually the difference.

3. Broach: spline count and shape

The broach is the top of the stem where the handle grips. Most are splined with small teeth. To count them, put a dot of marker on one tooth, or wrap the broach in masking tape, press it with a fingernail so every tooth shows, then peel it off and count the marks flat on the counter. Common counts are 16, 18, 20 and 22. Some broaches are square, D-shaped or another shape with no teeth at all; note the shape instead.

4. Type

A brass stem with a washer on the bottom is a compression stem. A cylinder with ports in the side and no washer is a cartridge. One handle that controls temperature on a tub and shower is a pressure-balance or thermostatic cartridge. The center handle of a three-handle shower is a diverter. If you are not sure, the part types page has a drawing of each.

5. Diameter (ceramic cartridges)

Ceramic disc cartridges for single-handle faucets are sized by the diameter of the body in millimeters. Measure across the widest part of the body. 35mm and 40mm are the most common sizes, with 25mm, 47mm and others also in use.

Hot or cold

Some valves use separate hot and cold stems that turn in opposite directions. Before you take both out, mark which side each came from with a piece of tape.

Put it together

Take your length and spline count to the identify tool. It lists every indexed part within a sixteenth of an inch, sorted by how close the length is. Compare the shape of your part against the listing before you buy, and if nothing matches, send us the measurements and a photo.