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A Hose Is A Hose

This winter, take time to squeeze the hoses.

Claim #0705698: When a 32-foot sailboat sank at a New York dock last summer, the investigating surveyor noted that the hose connected to the engine-cooling water intake was cheap radiator hose from an auto parts store. The flimsy hose had softened and split where it connected to the through-hull. Further inspection revealed that radiator hose was used nearly everywhere: cockpit drain lines, fresh water lines, bilge pump, and even the diesel fuel fill.

There is no such thing as an all-purpose hose on a boat; no single hose type can withstand engine exhaust, bring fresh water to the galley, safely transport gasoline to the carburetor, drain the cockpit, and flush the head. Using the wrong hose can cause problems that range from an inconvenient mess, to a burning boat.

Fuel Hose

Special Needs: Chemical resistance and low permeability. Gasoline-powered boats have specific requirements for hose that are so demanding they're federal law. Hoses that carry gasoline must be USCG approved and are marked with J 1527 A1, A2, B1, and B2, as well as with the manufacturing date. Gasoline hoses are usually made of rubber compounds. A-type hose is thicker than B-type and has to pass a 2.5-minute burn test (which is designed to give you enough time to get off the boat in the event of a fire), while type 1 hose is far less permeable than type 2. In the end, it makes senses to just use the best — A1 — for all gasoline uses. A new hose, called A1-15 is even less permeable and will become more and more common due to EPA regulations. Manufactures say that gasoline hose has a useful life of about 10 to 20 years. This kind of hose deserves the best hose clamps and ABYC standards require that gasoline fuel fill hoses be double-clamped. While there are no federal regulations for diesel-powered boats, A1 hose is also the best to use; the extra thickness guards against chafe and since it is less permeable, it is less likely to smell like diesel.

Bilge Hose

Special Needs: Low restriction. Bilge pump hose needs to be extremely flexible, strong enough to resist attack from chemicals, and it needs smooth internal surfaces to allow water to flow freely. Corrugated hose, seen in many installations, saps as much as 30 percent of the bilge pump's capacity because it creates extra friction. Bilge hoses are usually vinyl to maximize flexibility. Bilge pumps won't work well (or at all) if the hose has rises or loops where water can get trapped; the pump may not be able to overcome the resistance. (See "Stacy's Bilge Pump," April 2006).

Potable Water Hose

Special Needs: Chemically inert. Hoses that carry drinking water have to be made of FDA approved nontoxic materials (stamped on the hose) so that chemicals from the hose don't leach into the water; the chemicals also make the water taste bad. PVC hose is usually used for this purpose and systems that have pumps to deliver water under pressure or have hot water should use a reinforced type. While many potable water hoses are clear, opaque hose has the advantage of preventing slime from forming. Even clear hose that is hidden behind lockers will eventually get growth inside. Once slime gets started, it can be killed by allowing a bleach solution (three-quarters of a cup per 10 gallons) to remain inside for a few minutes, but getting the residue out is nearly impossible without removing the hose and running a rag through it.

Holding Tank Hose

Special Needs: Low permeability. While a leaking seawater hose might do the most potential damage, few people would argue that a burst holding tank hose is the most dreaded. Holding tank (sanitation) hose, aside from being strong, also has to have the least permeability possible — a delicate nose can detect the wrong hose. In fact, the best way to locate the source of a holding tank odor (more often than not, it's the hose) is to run a clean cloth over the hose and take a sniff. If it smells icky, the hose is permeating and needs to be replaced. The best sanitation hoses are thick-walled and smooth inside. Reinforced PVC is a good choice, but it should be made specifically for sanitation use. Hoses should be run so that there is no standing water in sags or loops to prevent premature aging and permeation. Eventually this kind of hose will get clogged with scale from seawater. With luck, the hose can be removed and banged around enough to loosen the scale, but by then, it probably makes sense just to replace it.

Through-Hull Hose

Special Needs: Strength. Through-hull hoses are really just an extension of a hole in your boat, connected to an above- or below-waterline fitting. As such, they must be exceptionally strong and long lasting. Hoses that are used at water intakes need to be rigid enough to withstand suction from engine raw-water pumps. Throughhull hoses are typically rubber, which has been reinforced with metal or plastic spirals. Don't make the mistake of thinking that automotive radiator hose is strong enough just because some of it's reinforced too — it's thinner and chances are the metal reinforcement will rust from seawater and further weaken the hose. Proper hoses are stiff and it's important they are not be bent too far, otherwise a weak spot will be created. This is one type of hose that deserves to be double-clamped, if there is room on the fitting. The lifespan of these hoses varies with their job, but hoses that are over 10 years old should be considered suspect.

Exhaust Hose

Special Needs: Temperature resistance. Exhaust hose is one of the most critical hoses on board. A leaking hose will not only flood the boat with cooling water, but it will also release deadly carbon monoxide, which is why the ABYC standards call for double-clamping of all exhaust hose connections. Most exhaust hose is rubber and designed to withstand temperatures to 250ºF. Some special silicon rubber exhaust hose can withstand up to 500ºF. If your engine's cooling water system fails, the exhaust hose is often first to suffer since it takes the full brunt of hot exhaust gases; the higher its temperature rating, the longer it will hold together. If you experience serious overheating, your hoses may look fine, but are likely to be damaged on the inside and should be replaced immediately. Even if the engine has never overheated, check regularly for bulges, cracks, and soft spots. Long runs of exhaust hose need to be well-supported, since they may be full of water and heavy.

LPG and CNG Hose

Special Needs: Flexibility and low permeation. Leaks in a liquefied petroleum gas (LPG) system (also called propane) can be catastrophic, which is why propane hoses must have permanent connections and cannot be hose-clamped to a barb like most other hoses. LPG hose is thermoplastic and sold in specific lengths with fittings already attached. Chafe is the enemy of this kind of hose, which should be protected wherever it passes through a bulkhead. LPG hose must be marked UL 21. CNG (compressed natural gas) is different from LPG and requires a different hose, which must meet the requirement of NFPA 52 for automotive hose.


1. Hoses are sized by their inside diameter (ID) and hose fittings are labeled based on the ID of the hoses.

2. Hose should be well-supported and not allowed to sag.

3. One of the best ways to inspect hoses is to squeeze them. If they feel mushy, crumbly, or excessively hard, they are beyond their useful life. Also, look at the ends — if they're splitting or swollen, the rest of the hose is in just as bad shape even if you can't see it. Hose that has standing liquid in it, whether effluent, gas, or water, won't last as long, which is why it's important to make hose runs that won't trap liquid.

4. Use the best marine grade 316 stainlesssteel hose clamps. Replace any that are even slightly rusted and double-clamp critical hoses. Clamps that are embossed rather that perforated are much stronger and longer-lasting.

5. Stiff hoses can be easier to install if the end is dipped in boiling water; this allows the end to stretch easier. When shopping for hose, if it is not marked properly (A1, etc.), it doesn't meet the standards, no matter what the salesperson says.