What F78 Means
F78 means the leak sensor has detected water. GE's guidance is to determine the source of the leak and correct it, or contact a plumber. A water heater holds many gallons under pressure, so a leak that is found early is worth acting on before it becomes a flood.
Common Causes of F78
- Leaking inlet, outlet or drain valve fitting
- Temperature and pressure relief valve discharging
- Condensate overflow mistaken for a leak
- Tank corrosion or failure
- Wet leak sensor reporting after an earlier spill
🔧 One Safe Check You Can Try
Look at the floor around and under the heater and dry it so you can see whether water returns. Check the obvious fittings - the cold inlet, the hot outlet, the temperature and pressure relief discharge pipe and the drain valve - for drips, without loosening anything. If you find an active leak, close the cold water supply to the heater, switch off its breaker, and call a plumber. Do not ignore it because the amount looks small.
⚠ Why You Shouldn't Go Further Than That
- Water heater plumbing is pressurised and hot - tightening the wrong fitting can turn a drip into a flood.
- A discharging relief valve can indicate excess pressure or temperature, which needs proper investigation rather than capping off.
- Damage caused during a repair attempt may not be covered - check your warranty terms first.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.