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Marine Sanitation & Seacock Replacement — 11m Flybridge Cruiser

A blocked toilet system led us below the waterline to a far more serious find — a badly corroded seawater-intake seacock that could have sunk the vessel. We rebuilt the black-water system and renewed every below-waterline fitting before relaunch.

11m flybridge motor cruiser GCCM Shipyard, Coomera QLD Delivered June 2026
Marine Sanitation & Seacock Replacement — 11m Flybridge Cruiser
The Brief

An 11-metre flybridge cruiser came into our GCCM shipyard with a blocked, unreliable toilet system — but the real story was below the waterline. Inspecting the black-water system, our engineer found the primary three-way diversion valve seized solid and the main toilet discharge hose completely choked. A check of the seawater side then uncovered something far more serious: a badly corroded below-waterline intake seacock that could have flooded the vessel had it failed at the berth.

We rebuilt the marine plumbing and sanitation system end to end — replacing the seized diversion valve, cutting out and renewing the solidified discharge hose, checking the macerator pump, and re-making every joint with new marine-grade hose clamps. The bilge and heads were cleaned and disinfected, and the system was pressure-tested from the toilet both overboard and to the holding tank, with no leaks detected.

The corroded seawater intake was cut out and replaced with a new bronze through-hull, seacock and hose tail, bedded in Sika 291 marine sealant and properly bonded for galvanic protection. The existing discharge seacock was wire-brushed, inspected and improved with a new elbow for better flow. The vessel was relaunched within her hardstand window — every below-waterline fitting renewed and certified leak-free, and a genuine sinking risk eliminated before it became an emergency callout.

Scope

Services rendered

Black-water system inspection & report
Seized 3-way diversion valve replacement
Blocked discharge hose renewal
Macerator pump service
Corroded seacock & through-hull replacement
Sika 291 bedding & galvanic bonding
Leak & pressure testing
Bilge clean & disinfect
Gallery

From the project

Aerial view of a motor boat carving a circular wake across clear blue water

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