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. Well start with a visual guide to common marine hoses, then go into more detail about each type. (See photo above).
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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. Theyre 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, its 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 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 dont leach into the water. Chemicals can also make 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. There are essentially two types of vinyl hose, reinforced and non-reinforced. You can tell them apart because reinforced has synthetic fabric strands visible while the non-reinforced does not. Reinforced is always the better bet as it resists kinking, is stronger, and is less likely to collapse especially when used on the suction side of a pump.
PEX is often a good choice on larger boats with long pipe runs where its semi-rigid structure and resistance to sagging makes for a neater installation with fewer supporting clips or brackets needed. PEX, short for polyethylene, comes in various colors, often blue for cold and red for hot, although grey is common too. All PEX piping has similar properties irrespective of the color.
Tip: Even clear hose that is hidden behind lockers will eventually get growth inside. It can be killed by flushing a bleach solution (3/4 cup per 10 gallons) through the pipework but be sure to flush the system with plenty of clean water before drinking.
Properties: Low permeability
The best sanitation hoses are thick-walled and smooth inside. Reinforced PVC is an excellent choice. Hoses for sanitation use are clearly marked, most often with the words sanitation hose printed in a stripe running the length of the hose. Although its tempting to use other types of hose that may be more flexible, dont. Smells and other problems are sure to follow. Aside from being strong, holding tank (sanitation) hose must have the least permeability possible.
Hoses should be run, as far as practicable, so that there is no standing water in sags or loops to prevent premature aging and permeation. This kind of hose eventually can get clogged over time with scale by waste and uric acid from the head. Using incorrect hoses have caused all sorts of problems really foul smells caused by using the wrong type of hose has rendered many a boat unusable.
Tip: Most holding tank odors come from the hose. To check, run a clean cloth over the hose and take a sniff. If it smells icky, the hose is permeating and needs to be replaced.
Properties: Strength
Thru-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. Thru-hull hoses are typically made from rubber that has been reinforced with metal or plastic spirals and may be double or even triple walled. Hoses that connect to underwater fittings should be manufactured to SAE J20R3 as a minimum and marked as such on the outer surface.
Dont assume that automotive radiator hose is strong enough just because some of it is reinforced. Its thinner, and the metal reinforcement may rust from seawater and further weaken the hose.
Thru-hull hose is stiff, and its essential you dont bend them too far or youll create a weak spot and/or a restrictive and possibly damaging crimp. The lifespan of these hoses varies, but hoses that are more than 10 years old should be considered suspect. And although ABYC doesnt require it, this is one type of hose that deserves to be double-clamped, if there is room on the fitting.
Contact us to discuss your requirements of marine exhaust hose. Our experienced sales team can help you identify the options that best suit your needs.
Tip: If you arent sure the thru-hull hose on your boat is rated for marine use, compress it between your thumb and fingers. Radiator hose is fairly easy to compress, whereas reinforced thru-hull cannot be squeezed nearly so easily.
Properties: Tempurature resistance
The 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. (This is why ABYC standards call for double-clamping of all exhaust hose connections.) Most exhaust hose is made from rubber and designed to withstand temperatures to 250 F. Some special silicone rubber exhaust hose can withstand up to 500 F and is often blue, making it easy to spot. If your engines cooling water system fails, the exhaust hose is usually first to suffer because it takes the full brunt of hot exhaust gases. The higher its temperature rating, the longer it will hold together.
If you experience severe engine 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, regularly check 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.
VETUS marine exhaust systems are based on wet systems. This is the process in which the cooling water is injected into the exhaust line. This reduces the gas temperature along with reducing fumes.
With the engine being at the heart of any vessel, it is important to fit the correct engine exhaust system. This will reduce maintenance costs, increase performance and is also safer for the crew.
The system is often hidden but plays a vital role in making sure the crew are not exposed to toxic exhaust gases by transporting these safely away. It also transports raw water or sea water and protects the engine against water ingress.
The main components of the exhaust system are the mixing elbow, the waterlock and the gooseneck. Additional components are an exhaust alarm and an air vent. There are also lesser-known options such as a gas water separator for a very quiet installation.
The first part of a well-designed wet marine exhaust system is the intake grate which only allows the engine cooling water to be sucked in when the engine is running and will filter the water to make sure items like plastic bags are not sucked up.
The mixing elbow is where hot exhaust gases of up to 400 degrees Celsius are mixed with cold cooling water with temperatures dropping to around 40 or 50 degrees Celsius.
A flexible hose supplies cooling water to the impeller pump which moves the water through the heat exchanger where it is then forced into the mixing elbow. When installing the system, the hose should be kept as straight down as possible from the mixing elbow to the water lock to ensure a good mix of cold water and hot gases, if this is not possible, a swirler or mixer can be fitted.
A waterlock, which fits onto the hose, is used to pump the mix of exhaust gases and cooling water overboard. A VETUS waterlock of the correct capacity will prevent water backflowing into the engine. When the engine is stopped, the waterlock will collect the water in the system, preventing it from damaging the engine.
VETUS designs waterlocks to withstand temperatures found in exhaust systems and has developed special plastics to use instead of stainless-steel.
We prefer to use specialist materials for our waterlocks as it has a longer lifespan than stainless-steel. The drawbacks of stainless steel are that it needs oxygen to form a protective layer for longevity. This oxygen is not found in an exhaust system because the engine uses it to burn fuel. In addition, the acidic exhaust fumes will start to attack and corrode the stainless-steel.
Other features of our waterlocks include noise reduction capabilities and a drain plug for winter storage.
There are three steps to follow when choosing the correct waterlock.
The gooseneck will provide additional protection to the system, particularly against waves hitting the back of the boat. The gooseneck will create a high point in the exhaust system so water cannot enter the exhaust system. This high-point should be 45cm but dont go over 150cm as this will create excessive back pressure in the system. The gooseneck can be formed using a flexible hose or for easier installation, VETUS has developed a gooseneck with a rotating top or bottom.
For a quieter system, a gas water separator can be installed to separate the exhaust gases from the water. The water will then drain from the bottom and the exhaust gases will exit quietly out of a top fitting. On faster boats with a continuous downslope from the engine to the transom, a muffler can be fitted to dampen the exhaust noise.
The final part of the exhaust system is the transom connection which is typically fitted with a non-return valve so any waves are blocked before they can enter the system.
All VETUS diesel engines are equipped with an exhaust alarm which can also be retrofitted to a wet exhaust system. The alarm has a small sensor. This sensor can be installed in the muffler, the waterlock, or even screwed into the hose. It provides an early warning of problems with the cooling water flow and rising engine temperature. Usually, the engine temperature will rise before your exhaust temperature. If the engine temperature does rise, it can cause the engine to seize up, leading to significant damage.
When the cooling water injection point is less than 15cm above the waterline, the cooling system can siphon water through the intake when the engine is turned off. VETUS air vents will prevent the water siphoning into the exhaust system and into the engine itself. The air vent need to be installed at least 40cm above the waterline.
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