Your Diesel Water Separator, Explained

After having your boat in storage for the winter, you are ready for your first boat ride of the season and to have fun in the sun with family and friends. Unfortunately, your boat’s engine is misfiring and more than likely this is related to a contaminated fuel system issue with your diesel water separator.

Whether or not you run gasoline or diesel fuel in your boat, water has a tendency to find its way into your fuel tanks and onward into your fuel systems. Both gas and diesel fuels absorb water whether from humidity in the air or through natural condensation in the fuel tank. If you do not have the proper filtration systems installed, this water can enter the engine and cause misfiring and possibly extensive damage.

How Does a Fuel Water Separator Work?

A fuel water separator not only helps to remove contaminants and debris from your fuel before it reaches the engine, it also removes any water found in your fuel. As fuel enters the fuel water separator, it passes through a filter media (typically a 10 micron fuel filter water separator). This filter removes over 99 percent of the particulates in the fuel and acts as a barrier to any water inherently found in the fuel. Because water is denser than gas, the water sinks to a collection bowl at the bottom of the filter and is retained there. Depending on amount of fuel consumption and the humidity in your local environment, you should view the water level in the drain bowl and drain it at least weekly. If the bowl contains any water, open the valve at the bottom of the drain bowl and drain the unwanted water into a container for proper disposal.

How Do You Choose a Diesel Water Separator?

There are several factors to keep in mind when choosing a fuel water separator. These include the filter media rating, type of collection bowl, and the fuel consumption rate of your engine. There are different types of filters, and you must choose the right one for your needs.

FILTER RATING:
One of the specifications of a fuel water separator is the filter media rating. This is usually expressed in microns. As a rule of thumb, the larger the micron, the larger the size of the particle that will pass through the filter. You can choose either 2-, 10-, or 30-micron filters. Most general marine applications use a 10-micron filter. All of our Clear Flow water fuel separators are 10 microns.

COLLECTION DRAIN BOWL:
The collection bowl is a key component of a fuel water separator. As the name suggests, it collects all the water that is filtered out of the fuel. These bowls can be made of clear plastic, aluminum, or metal. Clear plastic bowls offer an easy method to visually inspect how much water is in the collection bowl and often have a built-in drain plug. However, plastic drain bowls are sensitive to high heat environments such as enclosed inboard engine compartments. They are not recommended for use in these types of engine system. On the other hand, an aluminum and steel drain bowl is well suited for high temperature environments, but there is no way to determine how full the drain bowl is, so they should be drained on a regular basis. We suggest draining the collection bowl weekly.

FUEL CONSUMPTION RATE (GALLONS-PER-HOUR):
The next important factor is the fuel consumption rate of your filter. Typically, the larger the engine, the larger your fuel water separator should be. As a general rule of thumb, the required flow rate of your fuel water separator is about 10 percent of the rating of your engine. As an example, a 200-hp engine would require a 20-gallons-per-hour (GPH) filter. Our CFS1020 diesel separator cleans your fuel at 20 gallons-per-hour (20 GPH).

How Do You Maintain the Separator?

A fuel water separator isn’t a “set it and forget it” kind of component. You need to inspect it and maintain it on a regular basis to make sure it is operating properly. To maintain your fuel water separator, look for the water collection bowl at the bottom of the filter and determine if there is any water in the bowl. If you see water, place a container under the collection bowl, unscrew the drain plug and let the water flow out of the bowl. It is recommended that you check the drain bowl weekly and replace the filter element every 300-400 hours of use. Likewise, it is recommended that you replace the entire filter assembly annually, typically at the beginning of the boating season. Lastly, don’t forget to re-tighten the drain plug after draining the water from the collection bowl.

If you don’t follow this simple maintenance schedule, the water collection bowl will fill with water and the water will ultimately pass through the filter and onto the engine system.

What to Do if Water is Already in Your Diesel Fuel?

If you suspect you have water in your diesel fuel, the first thing to do is to make sure by pulling a sample out of your tank. Using a pump, pull a small amount of fuel into a clear container. Let it sit overnight for 24-36 hours in a dark place. After this period, examine the fuel for signs of separation. Diesel is lighter than water, so the diesel will be on the top, and any water will be at the bottom.

BONUS: If there’s a thin black line between the water and the diesel, you might have microorganisms growing and might need to use a biocide as well.

If you’ve determined that yes, there’s water in the fuel, then let your container of fuel settle for a day with no movement, whether your container is your whole boat or a hand-carried can. Then there are a number of methods you could consider using to remove the water:*

1. For small trace amounts of water, consider adding a fuel additive with a methanol base. If you have a good fuel system, you can clean out the water by using a good fuel conditioner at a high rate about 3x normal.

2. Another way is to use a pump, either a hand pump, a primer pump for outboards, or something similar. Attach a small hose to the pump and make sure the hose reaches all the way to the bottom so you reach all of the water.

If you use either of these methods, remember to remove the fuel filter first, in order to drain any extra contaminated diesel fuel.

Do You Need a New Diesel Water Separator?

Clear Flow offers fully configurable options, including choices between 2-ports or 4-ports, and whether your drain bowl is centered or off-centered. Sometimes that off-centered drain bowl is the perfect option for dealing with tight dirty spaces. Our diesel products include:

CFS1015 Diesel Series Spin-on Fuel Filter Water Separator: 15GPH, so perfect for your 150-hp engine. Utilizes a 10 micron H & V Coalescer filter media and filters out 99% of contaminants

CFS1020 Diesel Series Spin-on Fuel Filter Water Separator: 20 GPH for your 200-hp engine. Also utilizes a 10 micron H & V Coalescer filter media and filters out 99% of contaminants

What Happens When There’s Too Much Water in Your Fuel Tank?

Americans use a huge amount of diesel fuel. Reports show that the United States consumed 47.2 billion gallons of diesel fuel in 2019 alone!

But what happens when that fuel gets contaminated with water? What does that do to your engine?

Water is a very abrasive substance and can cause unnecessary wear on your engine components. In particular, water can corrode fuel lines and cause damage to the fuel pump and fuel injection systems. It can also cause rusting of internal mechanical components, and most importantly, water is not compressible. If water enters the engine, it could cause the engine to seize, or at the very least cause the engine to sputter, or misfire.

If you are concerned you may have water in your fuel system, here are some common signs that your assumptions are correct: Rough idle or rough acceleration, misfires, steam in the exhaust, slow acceleration, and the engine will not start at all. A good way to check for water in your fuel system is to remove the fuel filter and dump the contents of the filter into a clear glass jar. Let the jar sit on a flat surface for 10 minutes. If the contents appear to have a clear bubble at the bottom of the jar after settling, this is an indication you have water in your fuel. Conversely, if the fuel in the jar is clear, this indicates there isn’t water in your fuel. Also, if you see any sediments in the bottom of the jar, this indicates there are “other” contaminants in your fuel, and at the very least your fuel filter should be changed and your fuel tank should be inspected.

What About Boats with a Removable Fuel Tank?

Some people think you can forgo the use of a fuel water separator if your boat has a removable fuel tank. Their rationale is that you can store these tanks inside, out of the elements. Unfortunately, this is not completely true. Unless your fuel tank has a hole in it, water doesn’t normally get inside your tank from an outside source (e.g., a rainstorm). Rather, water forms inside the tank via condensation, and/or through the attraction of water vapors caused by diesel, ethanol, or other blended fuels. Also, after spending a long day out on the water, you may not have the energy to haul the fuel tank in and out of your boat, so the tank spends time out in the environment which can lead to water getting inside it.

Protect Your Boat by Preventing Water from Entering the Engine

You invested a lot of money in your boat and you are ready to get out on the water! But, if you don’t put safeguards in place to prevent water from entering the engine, you will find yourself stranded at the boat dock and surrounded by a bunch of unhappy friends. Installing or maintaining a fuel water separator prevents the problem of water in your fuel system. It is a simple and inexpensive device that can ensure your boat’s engine is able to run efficiently. Keep in mind you need to maintain the device, but the maintenance process is simple and quick.

We hope you enjoyed reading this article and we have increased your knowledge of what a fuel water separator is, how it operates, and how to choose one. Whether you’re looking for an outboard fuel water separator or a diesel fuel water separator, our fuel filter water separators are compact, versatile, and fully configurable. If you have any questions about this article, or if you need a quality separator, please reach out to us at Clear Flow Filtration Systems today

* PLEASE NOTE: Advice from ClearFlowSys.com is for informational use only and is used at your own risk. Please consult with professional experts first before undertaking any mechanical repairs or adjustments.