Marine grade hose is used on boats because of its flexibility and makes installations easier in tight spots. Marine hoses are constructed for specific uses and if used for the application intended, they will provide the most resistance to chafe, movement, and damaging environmental conditions such as salt water, salt air, heat, and cold.
SYSTEMS
The fluid systems aboard a boat are potable water, sanitation, propane fuel, raw water, engine-associated systems such as fuel, coolant, intake, cooling, drains, and bilge systems. Each of these systems has a hose specific to the application.
Potable water systems for hot and cold water should be FDA approved for drinking water.
- These hoses are constructed of either reinforced PVC or vinyl, are non-toxic, tasteless, and odorless.
- The FDA provides numbers for the different hose ratings.
- Always check the manufacturers’ specifications, usually found on the roll box, for temperature range, use, and water pressure ratings.
- If using these hoses for hot water, the temperature range is important.
- For water tank fill and vent hoses, use the corrugated heavy wall vinyl hose, FDA numbers 145 and 146.
Wet exhaust system hoses are black rubber and should be able to withstand temperatures of up to 250 degrees Fahrenheit.
- These hoses are flexible for easier installation, and absorb engine noise, movement, and vibration.
- Unlike rigid pipe used in these installations, the hose is not subject to corrosion and cracking.
Sanitation system hose is either rubber or vinyl.
- They should be resistant to odor permeation, flexible, have smooth heavy interior and exterior walls, and be labeled for sanitation use.
- These hoses should be used in all parts of the sanitation system; from the toilet to the holding tank or other marine sanitation device (MSD) type, to the pump-out and vent fittings, and to the discharge thru-hull fitting.
- Keep the hose runs short with no loops, dips or kinks, and be sure the fitting connections are tight.
- If the installation is such that sewage will "sit" in the hose, or a run will be long, use the premium rubber hose in lieu of the vinyl hose.
Fuel system hoses are heavy, thick walled rubber with a two-ply or two-spiral reinforcement. Between the two-ply layers should be a wire helix in the premium grade hoses.
- They should be resistant to fire for 2 1/2 minutes by USCG standards (type A1 or A2). Type B1 and B2 hoses do not pass the USCG 2 1/2-minute test.
- Fuel hoses should be resistant to the degradation properties of fuel, permeation, abrasion, environmental conditions, and maintain flexibility.
- These hoses must be matched to fuel types and blends.
LPG system hoses are high-pressure thermoplastic assemblies from 5 to 40 feet in length with flare fittings on each end.
- These hoses must be protected from physical damage, be accessible for inspection, and supports provided (either clips or straps) to minimize damage from vibration.
- Provide close fitting, non-abrasive sleeves or sealants for lines when passing through decks or other watertight areas.
- They should be of continuous length from the appliance to the regulator, solenoid valve, and leak detector (if installed).
Raw water intake system These hoses bring outside (raw) water inside the boat to supply systems such as the engine cooling, refrigeration, sanitation, and air conditioning systems.
- Hoses for these applications should be rated for use below the waterline use, flexible, heavily constructed, and reinforced to minimize kinking and collapse if suction occurs with a clogged raw water screen.
Drainage system hoses drain shipboard systems such as sinks, showers, and cockpits.
- These hoses are below the waterline and should be rated for this use.
- Cockpit drain hoses should be flexible, and heavy walled reinforced rubber to resist kinking and carry large quantities of water without collapsing.
- Other drains, such as sinks and showers, can be the same type of heavy-duty reinforced hose used for potable water systems, as long as the hose is rated for below waterline use.
Bilge system hoses provide discharge for bilge fluids usually via thru-hull fittings.
- Choose a hose with a smooth interior surface. Corrugated interior surfaces reduce water flow.
- Select a hose that is flexible enough to resist kinking, abrasion resistant, heavy walled, and reinforced.
- These hoses are used below the waterline and should be rated for this use.
- Resistance to coolants, oil, and environmental conditions is also a consideration because of the location and use of this hose.
TIPS
- If a bend in a hose exceeds its bend radius, it will kink. Smaller, heavily reinforced hoses have a smaller bend radius than larger, un-reinforced hoses. Bend (not kink) the hose before buying if the installation requires a tight bend.
- Reinforced hoses can have multiple plies, either nylon, or wire reinforcement (often referred to as a wire helix) that adds strength and rigidity. Reinforcement of hoses prevents the hose from collapsing from suction, or from expanding and splitting when under pressure.
- Hoses used in pressurized systems should be rated for a "maximum pressure" consistent with its use.
- FDA approved hoses for potable water, are non-toxic and constructed from non-corrosive, contamination-free materials. These hoses do not contribute to any taste or odor to water.
- All hose diameter measurements refer to the inside diameter (I.D.). Hose fittings are sized to the inside diameter of the hose. In other words, a 1/2 inch fitting is sized for 1/2 inch I.D. hose.
INSTALLATION
- Hoses should be sized correctly for the fittings, double clamped (not overlapping) on the barb fitting with stainless steel clamps.
- Use the correct thread sealant for NPT threads.
- Protect the hose from damage, including kinking, crushing, abrasion, and excessive temperatures by carefully routing and supporting.
- Many hoses are installed more easily if the end of the hose is lightly heated with a heat gun or by dipping in hot water. Do not overheat or burn the hose which will permanently damage it.
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