E18 means SHP78CM5N did not receive enough water in time; a partly closed tap, kinked hose or dirty inlet screen is more likely than a drain blockage. Use the exact code to separate water inlet, drainage, foam, leak protection and internal faults. Do not order a part until the visible installation and removable filters have been checked. Restricted household supply reduces fill rate below the level the dishwasher expects at the start of the program. E18 reports insufficient fill; E22/E25 occur later during filtration or drainage and require different checks. Open the tap fully, straighten the inlet hose without moving the built-in unit unsafely, then close water and clean only the accessible connection screen per the installation guide. Run a short fill and listen for steady water entry. If E18 returns with full supply, record the code for Bosch service.
Models covered
Safety first
- Wear gloves around the sump because broken glass may be hidden. Do not tilt a built-in appliance or remove its base, side panels or wiring cover.
What the symptom may indicate
Checks in the right order
- Confirm the pattern
Restricted household supply reduces fill rate below the level the dishwasher expects at the start of the program.
- Prepare safely
Cancel the cycle, switch the dishwasher off, close the water valve and wait for hot water and dishes to cool before touching a filter or hose.
- Apply the official check
Open the tap fully, straighten the inlet hose without moving the built-in unit unsafely, then close water and clean only the accessible connection screen per the installation guide.
- Retest once
Run a short fill and listen for steady water entry. If E18 returns with full supply, record the code for Bosch service.
Stop and get qualified help when
- Stop and arrange service for water in the base, a heat or motor code, a leak that continues with the valve closed, or a code that returns after one empty test.
Next step
Repair, replace a part, or arrange a diagnosis?
Use the checks and stop conditions above to choose a cautious next step. A symptom alone never proves that the appliance has failed.
Resolve it without buying anything
Complete the 4 user-accessible checks in order. If normal operation returns and no warning sign remains, no replacement is indicated.
Replace only the confirmed part
If the checks isolate a worn or blocked component, match its complete reference to the exact appliance model before ordering.
This guide does not identify a replacement part. Do not order a generic component from the symptom alone.
Arrange a diagnosis before replacing the appliance
Stop at any warning sign listed above. A qualified diagnosis should confirm that repair is unsafe, unavailable or uneconomical before an appliance replacement is considered.
Sources used
- Bosch — Bosch's official material documents “Bosch SHP78CM5N error E18: water level too low” and the user checks retained here.
Last checked: 30 August 2026