Shower Faucet: Leaking-M-Core Valve

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The most common reason for a leaking shower is the cartridge. The full M-Core line includes two series of valve assemblies, each using a different flow cartridge. See the chart below for troubleshooting help.

Symptom	Solution
Continuous Leaking with the Handle in the Off Position Water Leaks From Handle Water Leaks Around the Escutcheon/Back Plate	New Installation: Tighten the cartridge nut-Confirm the cartridge and system have enough compression. Installation should be hand tight plus one quarter turn with a wrench. Confirm that the cartridge parts are in place and correctly assembled. Following the instructions in the article M-Core Cartridge Basics, verify that all parts are present, no seals are damaged or missing and the cartridge assembly is reinstalled in the correct order. Replace the flow cartridge. The cartridge number is based on the M-Core Valve series, *See Identify the Valve Series and Cartridge* Below. Existing Installation: Replace the flow cartridge. The cartridge number is based on the M-Core Valve series, See Identify the Valve Series and Cartridge Below**.
Water Leaks Behind the Wall	Call us at 1-800-289-6636 or Contact Us
Showerhead Leaks When Running the Tub Spout Only	This symptom is called Stacking, see article What is a Stacking Leak?

Symptom

Solution

Continuous Leaking with the Handle in the Off Position

Water Leaks From Handle

Water Leaks Around the Escutcheon/Back Plate

New Installation:

Tighten the cartridge nut-Confirm the cartridge and system have enough compression. Installation should be hand tight plus one quarter turn with a wrench.
Confirm that the cartridge parts are in place and correctly assembled. Following the instructions in the article M-Core Cartridge Basics, verify that all parts are present, no seals are damaged or missing and the cartridge assembly is reinstalled in the correct order.
Replace the flow cartridge. The cartridge number is based on the M-Core Valve series, See Identify the Valve Series and Cartridge Below.

Existing Installation:

Replace the flow cartridge. The cartridge number is based on the M-Core Valve series, See Identify the Valve Series and Cartridge Below.

Water Leaks Behind the Wall

Call us at 1-800-289-6636 or Contact Us

Showerhead Leaks When Running the Tub Spout Only

This symptom is called Stacking, see article What is a Stacking Leak?

Identify the Valve Series and Cartridge:

2 SERIES- A 2 Series M-Core valve handle rotates only to adjust the water temperature, the system only provides one level of water pressure. The 2 Series uses the 1212 flow cartridge.

For 2 Series Shower Only, see article 1212 M-Core Cartridge 2 Series: 3 Port Valve
For 2 Series Tub and Shower, see article 1212 M-Core Cartridge 2 Series: 4 Port Valve

3 SERIES-A 3 Series M-Core valve handle rotates to adjust the water temperature and pushes in and out to adjust the force or volume exiting the showerhead or tub spout. The 3 Series uses the 1213 flow cartridge.

For 3 Series Shower Only, see article 1213 M-Core Cartridge 3 Series: 3 Port Valve
For 3 Series Tub and Shower, see article 1213 M-Core Cartridge 3 Series: 4 Port Valve

For additional information on M-Core Shower products, visit Single Handle Shower: M-Core at Solutions.moen.com.

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