Creating Tank Access For Polishing Diesel Fuel
and Cleaning Storage Tanks

Seabuilt Tank Access System

Demonstration of

Tank Access Plates


(Diesel Fuel
tanks only)

304 Stainless
(Water /
Holding /
Diesel Fuel


Aluminum Tanks




Carbon Steel Tanks




Fiberglass Tanks




Iron Tanks




Monel Tanks




Poly Tanks




Stainless Steel Tanks




Gasket Meterial

3/32 70-D Buna-N



Stainless Steel


Never install the Access Plate System on tanks containing gasoline or other highly flammable liquids or gasses


You have experienced one or more of the symptoms of Bad Diesel Fuel, and you now recognize that the diesel fuel in the fuel tank of your marine vessel or equipment is in dire need of cleaning and the fuel, in order to be usable (and avoid the cost and hassle of disposing of a tank of diesel fuel) needs a good “Fuel Polishing“. Now you need to determine if you are able to get two hoses into the tank (one suction hose and one discharge/return hose) in order to perform the tank cleaning. The size of the hoses being used on your TK Series Portable Tank Cleaning System or MTC Mobile Fuel Polishing & Tank Cleaning System may be from one inch up to three inches in diameter, depending on the rated flow capacity of the Fuel Polishing System. Some fuel fill caps may be large enough to accommodate the hoses, but some may be too small, and others may have an anti-siphon device installed at the fuel fill that prevents you from accessing your fuel tank via this route. Now what do you do?

Creating Easy Access

The Seabuilt Tank Access Plates, available in 6, 8, and 10 inch cover-plate diameters and in either aluminum or stainless steel, provide an easy means to access fuel tanks. If your fuel tank has a number of baffles, as some marine and generator “belly tanks” may have, you may need to install a Tank Access between each baffle.

Installation is easy. Use the bolt ring as a template, a saber saw to cut the hole and a drill for the bolt holes. Note that minor bits of metal debris is likely to fall into the tank. This material should be suctioned out with the AXI Fuel Polishing unit prior to restoring the equipment to service.

No gasket sealer is needed. Just tighten the nuts supplied until the outer gasket is compressed and swells slightly from the edge of the outer plate, but do not over-tighten and severely distort the gasket. Make sure all surfaces are clean and dry during installation.

Some of our customers have had the cover plates modified to include a suction tube welded to the cover plate that extends down to the bottom of the tank as a suction line, and a shorter return line that acts as a return line. Ball valves or Quick Connections are attached to the tubes where space allows so that the hoses from the MTC Series Mobile Fuel Polishing System can be quickly attached. Permanent installation of fuel hose lines are also common for installations of Systems. The portions of tubes outside the tank may be extended from the tank access plate to a more convenient location for connection to the Fuel Polishing System hoses.

Installations of Access Plates on equipment with multiple tanks or baffles that necessitate more than one access point may be configured with a manifold to control the flow of fuel from different points to a single central FPS Series Compact Fuel Polishing System or an STS 6000 Series or 7000 Series Automated Enclosed Advanced Fuel Conditioning and Tank Cleaning System providing you with total control over the Fuel Polishing process.

Available Sizes

  • Cover Plate Diameter: 6″ – Hole Cutout: 4″
  • Cover Plate Diameter: 8″ – Hole Cutout: 6″
  • Cover Plate Diameter: 10″ – Hole Cutout: 8″

Frequently Asked Questions

Why do I need an Access Plate System on my tank?
The majority of tanks are manufactured and installed with no access; therefore no ability to be cleaned and maintained. Note: The Access Plate System is for use on water and diesel fuel tanks – never install it on a gasoline tank or other tanks containing highly flammable liquids or gasses.

How many Access Plate Systems do I need for my tank?
The number of plates is influenced by the size of the tank and the quantity of baffles. Typically one plate per baffled section of tank. Note: Some baffles have holes large enough to clean adjacent sections.

Is it safe to install an Access Plate System below the fluid line on the side of the tank?
Yes, this is fine.

How large of an Access Plate System do I need?
We recommend that you install the largest plate that your install situation will allow. The larger the hole, the easier it will be to access and maintain the tank in the future.

Do I need to drain the tank completely before I install the Access Plate System?
No, but be aware that the process of cutting and drilling on the tank will allow minor bits of debris to fall into the tank. It is best to drain the tank and clean it out completely before you finish the installation.

What do I use to cut the hole with?
Most tanks can be cut with a saber saw and the appropriate metal cutting blade. Have a couple of extra blades handy in case you wear out or break one.

What keeps the backing rings from falling in?
The outer gasket has a tight fit over the studs and prevents the backing rings from falling into the tank – even when mounted overhead.

Should I use a gasket sealer?
No, do not use any type of third party gasket sealer. It is unnecessary and may work against the gasket properties to seal.

How tight should I torque the assembly fasteners?
Tighten the nuts until the outer gasket is compressed and swells slightly from the edge of the front plate. Do not over-tighten and severely distort the gasket. Do not use gasket compound. Make sure all surfaces are clean and dry during installation.

Why are there extra fasteners that come with the Access Plate System?
We know how frustrating it can be to loose something during an improvement or maintenance project on your boat. This is our small way of supporting you in your endeavor.

Is the Access Plate System Coast Guard approved?
Coast Guard approval is not available for our type of product. Please see the response below from the USCG:

“The Coast Guard has different regulatory requirements for fuel, water and holding tanks based on service of the vessel and size. We do not “approve” fuel, water, or holding tanks and therefore would not “approve” clean-out/inspection ports for them.

We do not “approve” tanks. However, we have regulatory requirements for some types of tanks on some types of vessels. Requirements for recreational boats are in 33 CFR Part 183, for uninspected commercial vessels you need to look at 46 CFR Subchapter C, for inspected small passenger vessels 46 CFR Part 182. The larger commercial vessels have more requirements which are in their applicable subchapters. For inspected vessels the Coast Guard Officer In Charge, Marine Inspection (OCMI) will want to verify that the tanks to be installed are in compliance with the regulations.”

CDR David Grant McClellan
Commandant (CG-5213) Systems Engineering