By Tom Burden, Last updated: 7/11/2023
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Consider what can happen when a hose bursts. If you are lucky, you will only have nuisance repairs to electronics, engine or interior. If fate has it in for you, a defective hose can cause a stink if it’s the discharge of the head, cause a fire if it’s part of a gas line or even sink your boat if it’s connected to a thru-hull fitting. That’s why we recommend spending a little more on a high-quality marine hose that offers more durability and better performance in critical applications and why you should inspect your hoses frequently for signs of deterioration.
Your application will determine what kind of hose to purchase. Our selection of hoses encompasses most applications and is available in any length from a foot up. The following is a guide to match hose and application.
Raw water intake hoses ingest water from outside a boat to cool an engine, flush a toilet, cool an air conditioner or provide a fresh supply of water for fish in bait tanks. Use only hose recommended for “below waterline” connections. Depending on the application, raw water intake hose will have fabric, PVC or stainless steel spiral reinforcement that resists kinking and prevents the hose from collapsing when for example, an engine pulls a vacuum due to a clogged water intake screen. For engine raw water intake, we recommend Shield's Series-250 or Series-252 hose, both of which are reinforced with a metal wire helix to prevent collapse. For engine coolant circulation, Shields Series-135 hose, which is reinforced with polyester yarn spirals can be a good choice—however care must be taken not to exceed the minimum bend radius and the temperature rating of the hose. For an overview of hose applications, see the hose application tables below.
Drainage hose for cockpit, sink or shower needs to be flexible with strong walls and resistance against kinks and abrasions, but since they are under positive pressure, they generally don't require helical wire reinforcement..
Potable water hoses must be made of FDA-approved, non-toxic materials so they won’t cause bad taste in drinking water supplies. Pressurized freshwater systems must use reinforced hose to withstand pump pressure (approx. 40–60PSI). For fill and vent hoses in water tanks, extra-heavy-duty sanitation/water hose should be used, while reinforced rubber hose is the best choice for hot water up to 140°F.
Alternatively, you may use a reinforced vinyl hose reinforced with nylon braid. Examples include: Series 162 (polyester reinforced clear PVC hose), FDA approved; Series 140 VAC Standard (steel wire reinforced PVC hose); and Series 148 Multi-Purpose (vinyl helix hose) FDA approved, ideal for critical drain and fill applications.
Bilge pump hoses typically use corrugated polyethylene with molded cuffs because it is flexible, economical and resists oil, solvents and other waste that collects in the bilge. For better flow you should choose a hose with a smooth bore, abrasion-resistant cover and good anti-kink flexibility. Examples include: Series 148 Multi-Purpose (smooth-walled vinyl helix hose) FDA approved, ideal for critical drain and fill applications, and Shields Multiflex Hose (Series 141). Of the corrugated hoses, the best is Shields VAC Standard (Series 140) and Bilgeflex (Series 120).
Sanitation hose has to be tough, flexible and resistant to odors and toilet chemicals. Choose hose with a smooth bore, heavy wall and specifically labeled for marine sanitation use. There are two choices: white vinyl hose and sanitation hose. Both will eventually smell. We recommend only smooth interior wall hose because corrugated types trap waste and restrict flow. Rigid PVC does not pass odors but is stiffer and more difficult to route and does not connect directly to pumps and thru-hulls. Still it is possible to plumb part of the system with rigid PVC, switching to hose where necessary.
Reinforcement: Many hoses have reinforcement in the walls for strength and rigidity, and to prevent collapse or expansion under pressure. The reinforcements can be wire, yarn spiral or PVC/vinyl helix.
Burst strength: Hose used for discharge lines has to resist pressure. This so-called burst strength, measured in pounds per square inch (psi) depends on product design and diameter; small diameter hoses have greater burst strengths. Hose with multiple plies or helical reinforcement has greater pressure limits, which is important for pressurized water or exhaust applications.
Vacuum rating: Hose on the intake side has to withstand suction, a property that is measured with a so-called vacuum rating. Intake hose should have a vacuum rating of 20 or higher.
Temperature range: Mostly critical for engine cooling hose, but might also be important for pressurized hot water systems.
FDA-approval: Hose used in potable (drinking) water systems must be constructed from safe, non-toxic materials that are contamination- and corrosion-free.
Bend radius: For proper installation a hose should not be bent more than the minimum bend radius recommended by the manufacturer to avoid kinks and breakage. Especially important for sewage lines and bilge pump applications.
Sometimes a lubricant is needed to install a hose onto a fitting.
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Hoses are sized by their inside diameter (ID). Hose fittings are labeled based upon the ID of the hose they fit. In other words, the outside diameter of a 1/2" barbed elbow is liable to measure slightly greater than 1/2", but it will fit 1/2" ID. hose just fine. Smooth bore hose is recommended for all applications, since corrugated hose can reduce flow by as much as 30%. Hose needs to be matched to the fittings on pump, through-hull, deck fill, tank, etc. See below for some sizing guidelines. Some popular diameters by application:
Marine hose clamps are stainless bands that compress hose around barbed fittings. They can be made from a variety of metals, but quality ones are all stainless steel, including the screw, band, and other parts. T-Bolt hose clamps are much stronger and have a 360° clamping surface. They are used in applications with high pressure, heat, vibration, or other severe requirements, like exhaust systems. Two clamps are recommended for below-waterline connections. Thru-hulls, hose lube & sealant, etc. may be necessary to make a hose fit and complete your marine plumbing system.
There is no such thing as an all-purpose hose on a boat. No single hose type can withstand engine exhaust, bring freshwater 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. This handy run-down will help you identify one type of hose from another and assist in choosing the right hose for the job at hand. We'll start with a visual guide to common marine hoses, then go into more detail about each type. (See photo above).
1. Exhaust hose. Able to withstand temperatures to around 250 F, an exhaust hose is often reinforced with wire, which may be stainless, or other special reinforcement. Other, more expensive silicone hoses are capable of sustaining much higher temperatures.
2. Hot and cold PEX potable water pipe. Many modern boats use PEX tubing for hot and cold plumbing. PEX is available in three distinct grades: A, B, and C. Although all are perfectly acceptable for potable water, Grade A is the most flexible and easiest to run in the tight confines of a boat. Fittings are easy to connect to the pipe, although you may need special tools. PEX is not the only option for potable water, however (see 6).
3. Sanitation hose. Often white, with a smooth bore to prevent trapping waste that could lead to odors, sanitation hose has an expected lifespan of approximately 10 years.
4. Corrugated bilge pump hose. This cheap hose is often supplied with bilge pumps. While easy to run, cut, and bend, its ridged internal structure restricts flow, making it a poor choice.
5. Smooth-bore bilge pump hose. Although four times the price of corrugated types, smooth-bore bilge pump hose offers up to 30 percent greater efficiency.
6. Potable water hose. Potable water hose comes in both reinforced and non-reinforced types. They're easy to tell apart as the reinforced hose will have strong synthetic cord strands visible. This one is clear but opaque is generally a better choice for potable water because there is less chance of algae growing inside.
7. Fuel hose. Fuel hose must be marked as such and will be stamped A1, A2, B1, or B2. Older hoses are incompatible with fuel containing ethanol, so if yours is older than about 10 years, it's most likely due for replacement anyway.
8. Thru-hull hose. For any connections to thru-hulls, reinforced hose is the only way to go. A cheap hose may fail and sink your boat.
Properties: Chemical resistance and low permeability
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