Every boat should have a scupper valve as it is very important for boat safety. The water passes from one direction to another through suppers so it can drain off the excess water in your boat. It also has
an exit location so the water will release easily and your boat will be free of extra loads. The boat can get extra water for any reason such as rainwater, or any small leakage on the boat. It is dangerous to keep the water on the boat for a long time.
Scupper has a one-way valve so it can only release the water, not added it. Also, the conductor head helps to channel the direction of the flow of water into the hole. The scupper is usually located at the stern.

How to Install Scuppers on a Boat: Tips to Follow
If your boat is already designed to self-bail, you can also install the scupper by sealed them on the hole.
Things You Will Need
- A micrometer
- Screwdriver
- Tape measure
- Paint scraper
- End wrenches
- Drill bit
- Rags
- Hole saw etc.
Scupper Drain Installation Process
When answering the question of how to install a scupper on a flat roof, I have come to know that process of the installation is the key to do it rightly.
Setting process of the one-directional or both way valves is important to help the water to flow out in the hole and keep the deck clean and dry.
Measure the Deck Height
First of all, take a proper measure in your boat deck from the waterline. You have to find out if your boat is ready to carry a scupper.
Keep the boat on the water and put some loads on it. Check the deck height from the waterline. If the deck is high enough from the waterline, you can install one or more scupper on the boat roof or parapet wall.
Replace the Old Scupper
If your boat already has a scupper, you can replace it. There are many updated scuppers you will get in the market. It’s better to install them and enjoy new features. Take a small fishing line and wrap it around the old scupper to see the sealing condition.
After that, cut the sealant with a socket and take a hammer and gently knock the scupper. Just tap in on straightly so this way any dirt or debris will come out from the scupper.
Insert the Pipe on for Flapper Valve
After removing the scupper, take a small size PVC pipe and insert it into the mounting holes by tapping gently. It will remove the front side of the scupper. The valves have inside and outside transom.
So, removing the valve and pull of the transom is easy. After removing the old one, clean the area with vinyl and scrubber and let the area dry for some time.
Scupper Assembly Process
Most of the original scupper is a little smaller than the new one. But do not worry. You can trim out the new one and make the right measurement.
Carefully cut off the flange then remove the excess leftover with a blade. After the mounting holes are dry completely, apply silicone gel at the inside and outside of the transom borehole and let it sits for some time. This will allow you to remove the scupper easily in the future.
Install the Smaller Piece
Remember, you have to set small pieces inside the boat and big pieces outside the boat because they both will attach with together. Now lay down the big piece on the hole with your hand twist it firmly. The caulk and sealant will keep it fit.
After that, apply the holes with marine-grade sealant outside of the flange so that you can seal it with the outer piece properly. Apply caulk on the small piece so it could attach with the fringe edge properly. Now put the flange straight on the hole and screw the flapper on it.
Tighten the Screws
Go to the opposite sides and tighten the screws with a screwdriver. Keep the flapper open so you can hold it from the other side. Take a rag and wipe out any excess silicon.
Measure the Thickness
Go to the top of the ransom rail and measure the thickness with a micrometer. Now insert a scupper valve in the tub exhaustion and make sure the water can flow through the drain adequately.
Make a Drain Tube Hole for the Scupper Valve
Pick a spot to make a drain tube hole on your boat deck or roof or parapet wall. You need to use stainless steel material for wall scupper or hole scupper. Cause it will have weather resistant barrier and be tougher than copper scupper.
For two scupper valves, take an inside flange ring and separate the steel valves. Insert the ring on the outside hole slowly. The hole should be completely fit to the transom and have to be matched with the drain tube.
Final Process on Scupper Valve Placing on a Self-Bailing Deck
Apply silicone gel at the inside and outside of the transom, then install the flanges. Gently tap the scupper valves into the hole and keep the direction perfect.
Now install the all-flange ring and screw it with a scupper valve. Tighten the screws and bolt with a screwdriver from both inside and outside.
How Do Scupper Works on a Boat?
Scuppers mainly save your boat from sinking. If the boat has scuppers, it is called a safe bailing boat. The scupper should have been made with stainless steel to be heavy duty to use on the scupper hole.

When it fills the scupper hole it will flow out water from the boat when the boat faces high wave activity or rain. When the boat has excessive water, the hull gets lower slowly. Too many loads also damage the boat and reduce fuel economy. Scuppers are normally made of plastic, metal or bronze.
They are installed both inside and outside of the transom. Scupper valves are located at the outside of the transom and it opens when the boat hull is underwater. Even it works when the boat is running at high speed. This one-way valve only releases water.
So, water cannot enter. The valve is normally located at the right angle so the water can pass without any hazard.
How Do You Put a Drain Tube on a Boat?
There is a hole on the boat that you have to put the drain tube on it. Tap the hole with a hammer gently. Now take the flensing tool and tighten the two sides with a pry bar. After that, you can insert the strain tube there. goes here!
Leave a Reply