Plumbing, water tanks and heads

The freshwater system includes tanks, deck fills, vents, selector valves, strainers, a 12V pressure pump, accumulator, distribution hose, faucets and often a calorifier/water heater heated by shore power and engine coolant. Tank material may be polyethylene, stainless, aluminum or integral fiberglass. A watermaker, if fitted, is a separate high-pressure appliance feeding this system.

The sanitation system includes a manual or electric marine toilet (head), intake, discharge hose, vented loops, Y-valves where legal, holding tank, vent, deck pump-out and possibly a macerator. A joker valve is the flexible one-way outlet valve limiting backflow into the bowl. Sanitation hose is odor-resistant and much more expensive than ordinary white PVC hose. All hose routes and valves must match legal discharge rules in the waters used.

Freshwater loss can end a passage plan; a split pressure line can silently pump a tank into the bilge. A failed water-heater heat-exchanger loop can affect engine coolant. Sewage hose or tank failure creates a health hazard and can make the interior uninhabitable. An incorrectly looped head can siphon seawater and flood the boat. Two-handed crews need simple isolation and a manual means to obtain drinking water.

Service by sanitizing freshwater tanks/lines, cleaning strainers, checking accumulator pressure, descaling where appropriate and rebuilding the head with model-specific seals/joker valve. A cycling pump may indicate a leak or accumulator setting, not pump failure. Replace one pump, hose run, valve or heater without redesigning the whole system when the rest is good.

Sanitation work should replace permeated hose end-to-end, correct low spots/loops and verify venting. Tank repair depends on material; access and removal often make a new tank preferable to welding. A manual head is maintainable worldwide and need not be replaced by an electric model for offshore use. Keep a spare pump kit/joker valve and a manual freshwater method.

• Covered by a standard survey — operation of pumps/toilets/faucets, visible tanks/supports, leaks, hose condition, water heater, vented loops/Y-valves and basic holding-tank installation. Surveyors do not usually fill every tank to capacity or taste/test potable water.
• Not covered — tank interior inspection behind baffles, water laboratory testing, sanitation permeation under all temperatures, water-heater pressure testing or long-duration leak tests. A plumber visit ($500–$1,500) is justified before purchase for sewage odor, hidden metal tanks, unexplained freshwater loss or illegal/unsafe head routing; routine service can wait.

• The broker or owner — “List each fresh and holding tank’s material/capacity/location and send replacement/cleaning invoices.” “Send dates/models for pressure pump, water heater, toilets and sanitation hose.” “Has any tank leaked, any head siphoned/backflowed, or potable water developed taste/odor?”
• The surveyor — “Fill and operate each pressure/head circuit where permitted, time whether the pump cycles with all taps closed, inspect tank supports/fittings and vented loops, and distinguish a service kit from a wholesale replacement recommendation.”

Turn the pressure pump on, close all taps and wait; repeated cycling means a leak, bad valve or accumulator issue. Inspect every low hose joint with a dry tissue. Smell the head locker, then press a warm damp cloth to sanitation hose and smell the cloth—odor transfer suggests permeation. Rock tanks gently and inspect straps/supports. Look for rusty heater seams and green coolant staining. Pump the head dry and check whether water creeps back into the bowl.