Marine Plumbing & Heads

The plumbing is where cruising boats develop their unique smells. Marine sanitation hoses, raw-water toilets, holding tanks, and seacocks all need ongoing attention — and ignoring them produces unforgettable problems. This is also the area where competent DIY pays off most directly.

What marine plumbing includes

Heads (toilets): Manual or electric. Macerator pump. Sanitation hose.
Holding tank: Capacity, vent line, deck pumpout fitting.
Raw water seacocks: Engine cooling, head intake, watermaker feed, refrigeration condenser, deck washdown.
Through-hulls and fittings: Bronze, Marelon, or stainless components.
Fresh water: Tank, pump, accumulator, fixtures.
Bilge plumbing: Pump discharge, manual backup, high-water alarm.

Maintenance schedule

Item	Interval	Notes
Head rebuild	2–4 years	Manual heads, cruising use
Sanitation hose check	Annually	Rub test for permeability
Sanitation hose replacement	10–15 years	Quality marine hose
Seacock cycling	Monthly	Prevent seizing
Seacock service	Annually	Disassemble, grease
Through-hull replacement	15–20 years	Bronze; sooner if galvanic issues
Fresh water pump	5–8 years	Diaphragm wear

Common costs

Service	Common range (USD)	Notes
DIY head rebuild (parts)	$50–150	Service kit
Pro head rebuild	$200–500	Labour plus kit
Sanitation hose replacement	$200–500	Materials
Hose replacement labour	$400–1,000	Depends on access
New seacock installation	$250–500 each	Haul-out required
Composting head conversion	$2,000–4,000	All-in

Frequently asked questions

Head rebuild frequency?

Manual heads every 2–4 years cruising. Electric longer but harder to fix at sea.

Sanitation hose life?

10–15 years quality marine hose. Replace when rub test shows odor permeation.

Seacock maintenance?

Cycle monthly. Service annually. Replace if won't turn.

Composting heads?

Increasingly common. $2,000–4,000 all-in conversion. Eliminates hose and tank.

Head repair cost?

DIY $50–150. Pro $200–500. Full replacement $600–1,500.