This is caused by either a restriction in the system or an installation issue.
- Remove the tub spout and inspect for any obstructions that may restrict the water from the spout. Turn the water on and see if the water comes out of the showerhead; if it does not, the issue is with the tub spout. If it cannot be freed of any obstructions, then replace the tub spout.
- Inspect the type of pipe used for the installation. From the tub port of the valve, only ½" Copper or ½" Galvanized Iron pipe (IPS) can be used. If PEX or CPVC was used from this connection, it will need to be replaced with either ½" Copper or ½" Galvanized Iron pipe.
- Measure the distance between the tub spout and the valve. The tub spout can be no less than six inches and no greater than eleven inches below the valve. If the measurement does not meet these criteria, it can cause this to occur.
- There should only be one elbow from the tub port of the valve to the tub spout. If there are multiple elbows, they will need to be eliminated.
- If any transitional fittings that might restrict the water flow were used, they will need to be removed.
- Inspect the valve body. If it was installed upside down, it will need to be reinstalled in the correct orientation. Many valves will have the word "up" printed on the valve.
- If this is a two-handle model, then inspect the flow director (diverter) in the valve. Depending on the location of the water supplies, it may need to be reversed.
Note: If there is no longer any access into the wall, then a volume control valve (Moen part number 91888) can be installed between the shower arm and the showerhead. This will allow the user to turn the showerhead on and off at their discretion, however, this will not provide a positive or complete shut off.