Why is my boat watermaker not working, and what should I check first?
My watermaker has stopped putting fresh water into the tank, although the control panel comes on and I can hear a pump running. What should I check first, and how can I tell whether it is a blocked filter, pump fault or membrane problem?
Answer
Check the power supply, seawater inlet, sea strainer and prefilters first: loss of power or restricted feed water can stop production without a membrane fault. Then check whether the pump runs, brine leaves the boat and product water reaches the diversion valve, as each points to a different fault.
Start with the supply
Record the alarm message before resetting anything, and identify the make, model and supply voltage. A Spectra Cape Horn Extreme 330 and a Newport 700c/1000c have different controls and troubleshooting procedures; their pressure settings are not interchangeable.
Isolate electrical power before disturbing wiring, close the seacock before opening seawater components, and release system pressure before loosening any pressurised fitting.
- Check the inlet seacock. Confirm it is open and the intake is clear of weed, plastic or other obstructions.
- Inspect the sea strainer. Clean the basket and check that the lid seal is seated properly. A suction leak can admit air without dripping seawater into the bilge.
- Check the prefilters. Replace dirty cartridges with the grades specified for the installation. Many systems use staged filtration, commonly 20 micron followed by 5 micron, but follow your manual.
- Check power at the equipment. Inspect the breaker, fuse, isolator and connections, then measure voltage at the pump while it is commanded to run. An idle battery reading will not reveal voltage lost through a poor connection under load.
After opening the filter circuit, prime and vent it using the manufacturer's procedure. Avoid repeated dry starts.
Pump noise and cycling
A silent pump calls for an electrical check before you order a replacement. If the display works, look for loose pump wiring, an active tank-full switch, a failed relay or an overheated speed controller where fitted. On Newport systems, a sleeping or disconnected display can also look like complete power failure.
On the Cape Horn Extreme's Shurflo feed pump, the pressure switch sits on the pump head and has two red wires. With power isolated, a competent owner can check switch continuity against the manual. A failed switch, motor brushes or internal thermal protection can prevent operation even when supply voltage is present.
A loud pump points first to a blocked intake or air entering the suction side. Check the strainer seal, hose connections and freshwater-flush module for air leaks, then re-prime. On relevant 48 V Newport installations, also check that the boost pump operates.
A pump repeatedly switching on and off may be reaching its overpressure cut-out. Check restrictions, accumulator charge and the specified switch setting before adjusting anything. Do not bypass the pressure switch as a routine remedy.