Dishwasher
E18
The E18 error code on a Siemens dishwasher means the machine isn’t getting enough water — or isn’t filling fast enough. It’s a moderately serious fault that will stop your dishwasher from running, but in many cases it’s something you can fix yourself in under 30 minutes.
What does this error mean?
E18 is Siemens’ water inlet error. The dishwasher’s control board monitors how long it takes for the machine to fill with water; if it takes too long or fails entirely, it throws E18 and stops the cycle to prevent damage. In plain terms: water isn’t reaching the machine at the rate it expects. This could be a supply problem, a blockage, or a faulty inlet valve.
Est. repair cost
£80–£150 professional repair (inlet valve + labour); £20–£45 DIY (replacement inlet valve or Aquastop hose)
🔍 Likely causes
🛠️ Step-by-step fix
Turn off the dishwasher and cut the power at the wall. Check the water supply tap under the sink — make sure it’s fully open. This is the most common cause and takes 10 seconds to check.
Pull the dishwasher out slightly and inspect the inlet hose running from the tap to the machine. Look for kinks, sharp bends, or anything pinching the hose. Straighten it out if needed.
Turn off the water supply tap, then disconnect the inlet hose from the back of the dishwasher (have a towel ready). Locate the small mesh filter inside the hose fitting and rinse it under the tap to clear any limescale or debris. Refit securely.
Check your household water pressure isn’t the issue — run a cold tap elsewhere in the house. If flow is unusually weak, contact your water supplier before going further.
If the Aquastop hose has triggered (common after even a small drip under the machine), you’ll need to replace the Aquastop inlet hose assembly — these are non-resettable safety devices. Replacement hoses cost around £20–£40 and are a straightforward swap for a confident DIYer.
If all of the above check out and the error persists, the water inlet valve itself has likely failed. This is a replaceable part but involves pulling the machine out fully and disconnecting the valve from internal wiring — if you’re not comfortable with this, call an engineer.
📞 When to call a professional
If you’ve checked the tap, hose, and filter and the E18 code keeps coming back, the inlet solenoid valve almost certainly needs replacing — this is the point to call a dishwasher repair engineer. Tell them: ‘My Siemens dishwasher is showing error code E18, I’ve checked the supply tap, inlet hose, and filter, and I suspect it’s the water inlet valve.’ This saves diagnostic time and money.
⚖️ Repair or replace?
A professional repair for an E18 fault — typically an inlet valve replacement — will cost £80–£150 including labour in the UK. If your Siemens dishwasher is under 5 years old, repair is almost always worth it; Siemens machines are mid-to-premium quality and built to last 10–15 years. If it’s over 8–10 years old and this isn’t the first fault, weigh repair cost against a new machine (budget £400–£700 for a comparable Siemens model).