Why does my marine toilet keep running, and how can I stop it?
My boat's electric toilet sometimes keeps making a pumping noise after I release the flush button, and occasionally water continues trickling into the bowl. What should I turn off first, and how do I work out which part needs fixing?
Answer
A marine toilet that keeps running usually has a stuck flush switch or control relay, an inlet valve that will not close, or a siphon drawing water into the bowl. First establish whether an electric motor keeps running or water flows silently, as each needs a different repair.
Stop the flow
Before working on the toilet, isolate its electrical supply, close the relevant seacocks and shut off any pressurised freshwater feed to prevent electric shock or flooding.
If the bowl is rising, stop using the toilet immediately. On a seawater installation, close the inlet seacock; if water still rises, close the discharge seacock too. A freshwater toilet normally has a separate supply valve, though some installations require you to switch off the domestic pressure pump and release pressure at a tap.
Identify the sound before dismantling anything:
- Motor beneath or beside the bowl: usually the toilet's discharge or combined flushing pump.
- Domestic water pump elsewhere aboard: may be feeding a leaking flush valve, though another plumbing leak can cause the same symptom.
- Separate vacuum generator: on a vacuum toilet, persistent running commonly indicates a vacuum leak or failure to reach the switch's stopping point.
- Silent trickling or rising water: suggests an inlet valve fault, siphoning or discharge backflow.
Water enters after pumping stops
On freshwater electric toilets, inspect the inlet solenoid valve first. Grit, scale or a damaged diaphragm can prevent it sealing. If water keeps entering with the toilet's power isolated but stops when you close its freshwater supply valve, the inlet valve is probably failing to seal mechanically.
With water and power isolated and pressure released, inspect the valve's inlet screen and accessible internals as directed in the model's instructions. Clear any debris; replace a damaged diaphragm or complete valve with the correct part. Do not connect a seawater toilet directly to drinking-water plumbing: freshwater installations require the manufacturer's specified backflow protection.
On seawater systems, water entering while the intake pump is stopped suggests siphoning or pressure at the hull intake while underway. Inspect the inlet valve and anti-siphon arrangement. A vented loop must admit air when pumping stops; salt deposits can stick its small air valve shut.
Clean or replace the vent valve and check the loop's position against the installation manual, allowing for the boat's heeled waterline. The required height and position vary. On many pumped installations, the inlet loop belongs between the pump and bowl, as fitting it on the suction side can prevent priming.