Shower Temperature Won't Adjust? How to Replace the Flow Control Valve [2026]

If turning your shower's temperature dial does absolutely nothing, your stabiliser flow control valve has likely failed. This mechanical valve manages temperature by physically restricting water flow over the heating elements—the slower the flow, the hotter the water. In this guide, I’ll show you the step-by-step process to remove the solenoid, loosen the heat exchanger, and swap out the flow valve safely.

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Is Your Flow Valve Actually Broken?

Before you tear the shower apart, check for these "False Valve" symptoms:

• The "Summer/Winter" Dial: If it's winter and your shower is on the "low" setting, the water will feel cold. This isn't a valve fault; it's a setting issue.

• Blocked Shower Head: If the head is scaled up, it creates "back-pressure" that makes the valve feel stiff or unresponsive.

• Limescale in the Valve: Sometimes the internal plastic gears are just jammed with grit. Rotating the dial from full-cold to full-hot 10 times (with the power off) can sometimes clear a minor blockage.

You have to remove the solenoid first to get to the flow / heat control

so remove wiring and 2 retaining screws and pull free or 

see our post on that here

Now undo the 2 retaining screws for the flow / heat control valve 

When the screws are removed that hold the flow control in place 

you need to loosen the heat exchanger to get enough room to be able to get the flow control 

valve free , first remove screws from bottom of heat exchanger and the one retaining screw

on the side of the heat exchanger.

Watch the pressure switch at the top as it hooks into the micro switch this is 

another thing that could go wrong with this and the elements would not 

heat up and solenoid would not open to allow water to flow.

When refitting make sure you fit the o-ring seal 

back in place and screwing the retaining nuts up

When you fit the outlet pipe if it falls of like it did for me  do not forget the 

o-ring seal 

Symptoms of a Faulty Flow Control Valve

• No Adjustment: The dial turns, but the water temperature stays identical.

• Leaking from the Valve Body: Visible drips coming from the central plastic assembly behind the dial.

• Low Flow Even on Cold: If the internal gears or ceramic discs inside the valve seize or break.

Step-by-Step Replacement Guide

• Safety First: Isolate the electricity and water supply.

• Step 1: Remove the Solenoid: You cannot reach the flow valve without removing the solenoid first. Undo the two screws and pull it forward.

• Step 2: Loosen the Heat Exchanger: This is the "secret step." The flow valve is wedged tight. You must remove the screws at the base and side of the silver heating tank to give yourself enough "wiggle room" to pull the valve out.

• Step 3: The Pressure Switch: Watch the top of the valve where it hooks into the microswitch. If this isn't aligned correctly on reassembly, your heating elements won't engage.

• Step 4: O-Ring Integrity: Crucial Tip: Always check the O-ring seals on the outlet pipe. If they fall off or are pinched during reassembly, your shower will leak inside the box.

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• The "Limescale" Warning: Mention Flow valves often fail in hard water areas because limescale seizes the internal moving parts.

• Troubleshooting Tip: Before replacing the valve, check that your shower head isn't simply blocked—sometimes back-pressure makes the valve feel like it's not adjusting.

                  See the video below of us removing and replacing the                                           flow/heat control valve