Systems & how-tos
Freshwater and head systems on cruising yachts
How freshwater tanks, pumps, and marine heads work on Nordic cruisers — pressure systems, seacocks, and winterisation basics.
Overview
Freshwater plumbing delivers drinking and galley water from tanks to taps. Head systems move waste overboard or into holding tanks. Both depend on hoses, seacocks, and pumps that fail quietly until they flood or smell.
Freshwater loop
| Component | Notes |
|---|---|
| Tanks | Often poly under berths — inspect access plates for smell |
| Fill deck fitting | Must not share vent with diesel |
| Pump | Manual foot pump, pressurised diaphragm, or accumulator tank |
| Hot water | Engine heat exchanger or 230 V element — scale in Baltic hard water |
Pressurised systems need a expansion/accumulator to stop pump cycling. Low flow often means ** clogged filter** at the pump inlet, not a bad tap.
Marine heads
- Manual Jabsco-type — simple; rebuild kits yearly in heavy use
- Electric macerator — more parts; sensitive to wrong paper
- Holding tank — required in many harbours; know Y-valve position and lock
Seacock on the discharge line must open only offshore or at pump-out — fines in Sweden and Croatia for illegal discharge.
Winterisation
- Drain tanks or fill with food-grade antifreeze through all taps
- Pump antifreeze through head intake until pink exits overboard
- Close seacocks and label "winter — closed"
See spring commissioning for reverse steps.
FAQ
Why does my tank water taste bad?
Stagnant hose, algae in tank, or wrong hose type (non-potable). Flush with dilute chlorine, replace hose, then rinse thoroughly.
Next steps
Cross-read through-hulls and seacocks and watermaker vs marina water.