Do you have any idea how heavy a sit-on-top kayak is to carry when it’s full of water? Or how unpleasant it is to sit on the back of a boat with water sloshing around your feet? If you do, then you’ll understand why boat scuppers are so valuable. Surely it makes sense, doesn’t it, to get the water out of the boat?
Let’s begin by understanding what a boat scupper is
When you are out on the water, it is not unusual for some water to splash into the well of the boat. Or, if it rains, water will pool in the boat. This is when you need a scupper.
A boat scupper is the opening in the side wall of the boat that allows water to drain. This prevents the water from gathering and pooling in the body of the boat.
Now we know that, let’s look at the parts of a scupper
A boat scupper has different parts. The basic part is the housing, which is essentially a mount and tube that goes through the wall of the boat. Then there is a one-way valve, which only allows water to flow through it in one direction.
The valve is made up of a seal and a mechanism that will close it. When water presses on the boat from the outside, the valve is sealed by the pressure. When the water flows the other way, out of the boat, the valve is forced open.
Just like any part of a boat, not all scuppers are the same
The most common type of scupper is the one-way valve that allows water to flow one way and not the other. The flow is out of the boat and not back in.
A scupper doesn’t necessarily need a valve or plug, but there can be holes or tubes through the hull of the boat. Larger boats have openings in the gunwale through which the water can flow from the deck.
Smaller boats need dedicated drains or scuppers in the cockpit and going through the hull for water to drain to the outside.
The simplest boats have the simplest scuppers
Water can accumulate in any boat, from a simple kayak to a container ship out on the sea. All boats need to have some mechanism via which the water can either drain or be drained, from the deck. This is where scuppers come in.
It makes sense that the simplest boats will have the most basic form of the scupper. On a kayak, the scuppers are simply holes in the hull, through which the water will flow out automatically if the level of water is high enough, or when the kayak is tipped.
The problem is that a kayak sits quite low in the water, especially with people on board. Water splashes into the boat, but can also be forced up through the scupper holes. This is where scupper plugs are used to block the holes in the hull of a kayak when it is on the water.
They are removed when the boat is on the land and the water will drain out through the scuppers.
Then there are self-bailing boats, where the scuppers do it themselves
Self-bailing boats are designed to allow any water that may accumulate on the deck to drain on its own, as gravity forces the water out through the back of the boat. Scuppers are inserted that go straight through the back wall of the boat.
In the tube of each, a scupper valve allows the water to flow out of the boat but blocks the water from flowing up the hole into the boat.
Self-bailing scupper valves open automatically when a boat is moving and the pressure of the water on deck causes it to drain out through the scupper. At the same time, the water the boat is moving through cannot rise into the boat.
It seems logical that a scupper must go through the hull
A through-hull scupper is a tube that fits through the wall of the boat and has a rubber flap at one end. The flap will allow the water to drain out but closes again to prevent water from running back into the boat.
The flap is round and the same diameter as the pipe. It is supported halfway through the pipe so that it can flap open or closed. The direction of the flap is such that it opens when water runs out through the scupper, but will not open if water runs in from outside.
Seeing as a boat will be on the water, doesn’t it make sense to use a material that withstands corrosion?
Scuppers made of stainless steel is an attractive option because the material is very resistant to corrosion, which is a valuable attribute for a part that spends a lot of time with water flowing through it.
Boat scuppers made from stainless steel can be as simple as a drain that fits through the hull. This is in the shape of a tube, but has a 45° bend, so that water cannot flow in and upwards easily. At the outer end of the scupper is a grid, to catch debris.
Then, there is a stainless steel scupper with a stainless steel flap that is hinged in the middle. The hinge works so that the flap will seal if water enters from the outside and pushes against it, but will open if water flows onto it from inside the boat.
Of course, plastic scuppers are also highly resistant to corrosion, although they may still weather
There are all types of plastic and plastic composites available to boat owners. Scuppers can be made completely of plastic, or they may be combined with another material. A common mix is a plastic through the hull scupper tube with a rubber flap or disk. The housing of a ball lock scupper is often made of plastic.
Ball-lock scuppers are a bit like golf, the ball must end up in the hole…or not
A ball lock scupper uses the pressure of the water to move a ball into and out of position to close and open the scupper valve. These scuppers are often called ping pong scuppers.
When water is drained from the boat, the pressure sends the ball away from the hole and the water can escape. When the pressure of water coming into the boat presses on the ball, it is forced upwards into the hole and closes it.
Ball-lock scuppers can be mounted horizontally or vertically. Vertical is better because no water can drive up into the hole. With the horizontal mounting, trash can flow back out through the scupper and gets stuck. Quite often, all the water doesn’t flow out.
Straightforward scuppers use a rubber flap to seal the valve
The principle of any scupper is to allow water from the boat through and to block any water from outside the boat. This is achieved via a tube through the wall of the boat, which is alternately blocked and opened by a one-way valve.
Often, these valves are made of rubber. Most commonly, they are in the form of a flap that is positioned to flap up only in one direction, which is away from the boat. This allows the water to escape from the deck. When pressure is applied to the flap from the outside, it stays in position.
The problem with rubber is that it will eventually perish, so many scuppers are made from plastic or composite materials.
Sometimes, the name of a scupper says it all. Introducing the duckbill scupper
A duckbill scupper is a form of a through-hull scupper with a thermoplastic flap. Water pressure from outside causes it to seal, thus protecting the boat from any water entering.
The scupper itself is a tube that goes through the wall of the boat. The duckbill section is a rounded end of a pipe that fits into the end of a through-hull scupper tube. One end of the flap is flattened, resembling the wide, flat bill of a duck.
It can open vertically, like a duck’s bill (hence the name). When there is no pressure from outside, the water in the boat can flow through the opening. When the pressure of the water outside the boat increases, the flap seals, allowing no water in or out.
Imagine how useful it is to have a scupper that is one size (can be made) to fit all…
A telescoping scupper is one that can be adjusted to a range of lengths. This means it can be made to fit different widths of boat hulls. The transom of a boat is not always the same as another, so a telescoping scupper can be adjusted to fit snugly through the wall of the boat, making sure it is completely sealed at both ends.
FAQs
Does a boat scupper have to seal?
The simple answer is, no, a boat scupper doesn’t have to seal, as long as the water can drain out of it. However, if there is a possibility that water will force its way up the scupper, then a seal is not only valuable, it may be essential.
How do I know my boat’s scuppers are working efficiently?
The surest sign of a boat scupper working efficiently is if there is no water pooling on the deck of your boat. You can also check the flow of water out of the scupper when the boat is on land, or if you lift it and allow gravity to let the water flow out.
What is the best material for a scupper to be made from?
Choosing the material from which a scupper is made is part of the process of choosing the type of scupper. Your best overall choice is likely to be the material and scupper that will have the longest life and give the best service. Stainless steel and a thermoplastic composite may be the best choice then.