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Tiffin Motorhomes Knowledge Base

How do I fix or replace the fresh water tank fill / city water selector valve in the wet bay?

Fixing or replacing the fresh water tank fill / city water selector valve (sometimes called the “Anderson valve” or “diverter valve”) in your Tiffin’s wet bay is a straightforward but critical repair. Here's what you need to know:

🔍 Problem Symptoms

  • Water only flows to the tank or the city line—not both when switched
  • Water leaks from the valve or behind the wet bay wall
  • The handle feels loose, cracked, or spins freely
  • Valve is stuck and won't turn

🛠 Tools & Supplies You’ll Likely Need

  • Replacement valve (commonly a 2-way or 3-way brass diverter or Anderson valve)
  • Adjustable wrench / channel locks
  • PEX cutter or tubing cutter (if lines are crimped)
  • PEX fittings or SharkBite connectors
  • Teflon tape (for threaded fittings)

🔧 Step-by-Step: Replace the Selector Valve

  • Shut off all water
    • Disconnect from city water and turn off your water pump.
    • Open faucets to relieve pressure in the lines.
  • Access the valve
    • Open the wet bay panel. If necessary, unscrew and remove the rear service panel to expose plumbing behind it.
    • Label or take a photo of the lines so you remember which goes where.
  • Disconnect the plumbing
    • Use a PEX tool or release fittings carefully.
    • If SharkBite fittings are present, press the release collar while pulling the tubing out.
  • Remove the old valve
    • Unscrew or unclip the valve from its mounting.
    • Check for any broken internals or stripped threads.
  • Install the new valve
    • Reconnect all plumbing using either PEX crimp, SharkBite, or hose clamps (depending on original setup).
    • Wrap threaded fittings with Teflon tape to prevent leaks.
    • Secure the valve in place.
  • Test for leaks
    • Slowly turn the water back on (pump or city water).
    • Test both modes: Tank Fill and City Water.
  • Verify that pressure and routing work correctly and there are no drips.

⚠️ Pro Tip:

  • Tiffin often uses color-coded PEX lines and standardized valve types.
  • If yours is cracked or failing regularly, consider upgrading to a brass diverter valve if it's a plastic model now.
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