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Shower Faucet: Flow Issues- Moentrol with Integrated Transfer Valve

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Showering devices like showerheads and handheld showers are designed to provide varying flow rates. Before replacing or repairing your shower system, please confirm the flow rate (GPM /gallons per minute) of the device that is experiencing the reduced water output. Over the last 20 years the Department of Energy has changed the flow rates. Example: in the 1970's showerheads were rated at 3.25 GPM, In the 80's and 90's the acceptable flow rate was 2.5GPM and in the last 20 years flow rates have been reduced to as low as 1.25 GPM. With advances in plumbing technology Moen has developed showerheads that provide the luxury of a higher flow rate, while meeting Eco Performance guidelines. 
Symptom System Test Solution
Low Flow: Temperature Specific

A reduction in flow when operating one specific temperature. (Ex: Only when using hot water)

Is the reduction temperature specific?  Yes

Is the reduced flow happening when using a specific device?  No

Things to consider or test before a diagnosis can be made:

  1. Check Stop Valves: Your system is designed with a hot and cold check stop valve. If the shower has been recently installed or serviced you will want to confirm these are fully open as they may be contributing to your low flow issue.
  2. Confirm handle operation: Verify how each handle operates
    • Upper Handle This handle is designed to rotate to divert water (note: This handle can also be assembled to pull in and out. If the lever is able to pull in/out, it must be in the pulled out position to allow water flow).
    • Lower Handle In this shower valve system the lower handle pulls out and pushes in for on/off and volume control, and it rotates for temperature modification. 
  3. Please perform a SystemTest: Now that we've reviewed the information above let's recheck the flow with the lower handle pulled out, and rotated to the temperature experiencing the reduced flow:
    • If there is still a temperature specific reduced flow, continue to Step 2 in the Solution column for this symptom.
  1. Run a System Test.
  2. Clean the 1423 balancing spool, see article  Maintenance: How to Clean a 1423 Balancing Spool- Moentrol with Integrated Transfer Valve
  3. Replace the 1225 temperature/flow cartridge and 1423 balancing spool.
Low Flow: Overall

The shower system is delivering less flow than it has on previous occasions.

Is the reduction temperature specific?  No

Is the reduced flow happening when using a specific device?  No

Things to consider or test before a diagnosis can be made:

  1. Check Stop Valves: Your system is designed with a hot and cold check stop valve. If the shower has been recently installed or serviced you will want to confirm these are fully open as they may be contributing to your low flow issue.
  2. Confirm handle operation: Verify how each handle operates
    • Upper Handle This handle is designed to rotate to divert water (note: This handle can also be assembled to pull in and out. If the lever is able to pull in/out, it must be in the pulled out position to allow water flow).
    • Lower Handle In this shower valve system the lower handle pulls out and pushes in for on/off and volume control, and it rotates for temperature modification. 

3. Please perform a System Test: Test the flow with the lower handle pulled out and rotate through the temperatures:

  • If there is still an overall reduction in the flow, continue to Step 2 in the Solutions column for this symptom.
  • If there is a temperature specific reduced flow, review the symptom Low Flow: Temperature Specific.
  1. Run a System Test.
  2. Clean the 1423 balancing spool, see article  Maintenance: How to Clean a 1423 Balancing Spool- Moentrol with Integrated Transfer Valve
  3. Replace the 1225 temperature/flow cartridge and 1423 balancing spool.
Low Flow: Using One Function/Device

A reduction in flow operating an independent function from one shower device (showerhead, body sprays or hand held shower).

Is the reduction temperature specific?  No

Is the reduced flow happening when using a specific device?  Yes

Things to consider or test before a diagnosis can be made:

  1. Check Stop Valves: Your system is designed with a hot and cold check stop valve. If the shower has been recently installed or serviced you will want to confirm these are fully open as they may be contributing to your low flow issue.
  2. Confirm handle operation: Verify how each handle operates
    • Upper Handle This handle is designed to rotate to divert water (note: This handle can also be assembled to pull in and out. If the lever is able to pull in/out, it must be in the pulled out position to allow water flow).
    • Lower Handle In this shower valve system the lower handle pulls out and pushes in for on/off and volume control, and it rotates for temperature modification. 

3. Please perform a System Test: Now that we have verified the check stop valves are open and confirmed the handle operation, we will need to observe the flow from each shower function and note which function is experiencing the reduced flow (please keep in mind that each shower device may be designed to provide different flow rates. Also if your valve is a 3330/3320 (3F) you should also have a shared function.). Turn the water on by pulling the lower handle out.

  • 3350 Two Function Transfer Valves: Check the independent function for each shower device by rotating the upper handle counter-clockwise from function 1 to function 2.
  • 3320, 3330 Three Function Transfer Valves: Check each of the three functions by rotating the upper handle counter-clockwise from function 1 (one independent shower device) to function 3 (both devices run simultaneously) to function 2 (one independent shower device).
  • If there is still a reduced flow during one of the functions of the shower devices, continue to Step 2 in the Solution column for this symptom.
  • If there is an overall reduction in flow, review the symptom Low Flow: Overall.
  1. Run a System Test.
  2. Check for blockage in the shower device. The low flow symptom can occur if debris has come through the line and became trapped causing a reduction of flow:
  1. Is the flow of water normal with the shower device removed?
  • Yes, rinse any debris from the shower device and re-test the flow. If the symptom persists, replace the shower device.
  • No, replace the diverter cartridge:
No Flow

There is no hot or cold water from the shower system. 

Is the reduction temperature specific?  N/A

Is the reduced flow happening when using a specific device?  No

Things to consider or test before a diagnosis can be made:

1. Check Stop Valves: Your system is designed with a hot and cold check stop valve. If the shower has been recently installed or serviced you will want to confirm these are fully open as they may be contributing to your low flow issue.

2. Confirm handle operation: Verify how each handle operates

Upper Handle This handle is designed to rotate to divert water (note: This handle can also be assembled to pull in and out. If the lever is able to pull in/out, it must be in the pulled out position to allow water flow).

Lower Handle In this shower valve system the lower handle pulls out and pushes in for on/off and volume control, and it rotates for temperature modification. 

3. Please perform a System Test:

Test the flow with the handle(s) pulled all the way out for full flow and rotate the lower handle to check flow for cold/warm/hot temperatures.

  • If there is still no water flow, continue to Step 2 in the Solution column for this symptom.
  • If there's a temperature specific reduced flow, review the symptom Low Flow: Temperature Specific.
  • If there's an overall reduced flow, review the symptom Low Flow: Overall.
  • If there's a reduced flow from one specific device, review the symptom Low Flow: One Device.
  1. Run a System Test.
  2. Replace the 1225 temperature/flow cartridge and 1423 balancing spool.

For additional information on Moen products visit solutions.moen.com and select the type of faucet you are repairing. The faucet guide will contain repair details, troubleshooting and specific information on assembling handles associated with that style of product.

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