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What Is Fly Line Backing? Types, How To Tie, & How Much Is Needed?


Article Categories: Fishing Tips | Gear
Article Tags: Fly Fishing

Fly fishing is a highly technical sport that requires different gear than the more familiar bait/spin fishing and trolling. If you are new to fly fishing, these differences may be a barrier to entry, but that doesn’t have to be true! Anybody can fall in love with and understand the technical aspects of fly fishing. The first step is to understand clearly what the various pieces of equipment are meant to do. Here, we are going to help explain everything you need to know about fly line backing.

Before reading this article specifically on fly line backing, you may want to dive into our complete fly fishing setup explanation article.

Quick Navigation:
What Is Backing?
Who Needs Backing?
Types of Backing
How Much Backing Do You Need?
Saltwater Vs. Freshwater Backing Choices
Backing Alternatives
How To Tie Backing


What Is Fly Line Backing?

One of the biggest differences between fly fishing and other types of fishing is the line that is used. Fly fishing line isn’t one piece of monofilament or braided line kept on one spool, like a standard fishing line. It includes several different pieces: the leader, the tippet, the fly line, and the backing. At the end of the line is the leader and tippet, which are thin lines that the fish can’t see. This helps you trick the fish into thinking that your fly is their dinner.

The leader and tippet are attached to the fly line, which is a thicker piece of line that helps your fly either sink or sit on the surface of the water. This line may be weighted, or it may float. It comes in many different colors and varieties, and you may find that you want to use different types of fly line for different occasions.

The length of the fly line is usually between 90 and 110 feet, depending on preference. But that isn’t actually the full length of line you use on a fly rod. There’s one more part to the whole line, and that is the backing. Today, we’ll be focusing on fly line backing and the various options you have.

Fly Rod Setup


Who Needs Backing?

Depending on the type of fish you’re after, you might not need much backing. You might have about 130 feet of line on your rod with just your fly line, leader, and tippet— so if you’re going after panfish or small brook trout that don’t fight much, you might not even need backing. If you only cast out 30 feet of line, you’ll have more than 60 feet to bring those fish in. That’s very likely to be enough.

Even if fishing for smaller fish, it is always worth having at least a small amount of backing on your reel so that you have the capability to cast or let out all of your fly line in the occasional times where it may be necessary.

If you’re fishing for any larger species, or in fast water, you definitely want some backing on your reel, just for the insurance. In freshwater, carp, salmon, and steelhead commonly pull out enough line for you to need backing. If you’re fishing in saltwater, you need backing. You also want to make sure that you have backing when you’re fishing water with hazards or obstacles like fallen logs, snags, and large rocks. It’s better to have more line length to play within this environment.


Types of Backing

There are two varieties of backing that are generally used in fly fishing; however, there are some emerging technologies that make improvements on these two standards that we’ll discuss momentarily.


Dacron Backing

The first type of backing is Dacron backing. Dacron is the trade name for a tough polyester material called “polyethylene terephthalate,” or PETE or PET for short. PETE is a synthetic resin that was developed for and is still used in many of the world’s most common plastics. You can find PETE in everything from soda bottles to acrylic yarn, but its most frequent use is in food packaging.

Dacron is a thermoplastic and can be formed into many different shapes with applied heat. When spooled in long strands, it creates a tough synthetic line with a low coefficient of friction. This means that it slides over itself and through the eyes of a rod easily, making it perfect for fly fishing. Dacron line comes in many strengths and is the most commonly used type of backing in fly fishing, especially in circumstances where your fish will run less than 300 feet.


Gel-Spun Backing / PE Backing / Spectra Backing

The other main type of fly line backing is gel-spun backing. If you’re a saltwater fly fisher, this is probably the type of backing that you use. Gel-spun backing is made of another polymer called high-modulus polyethylene (HMPE). This material was developed for use in body armor, ultra-safe climbing ropes, and high-performance sailing lines.

The polymers in gel-spun material give it an extremely high breaking strength at a drastically reduced diameter. This is the major advantage of gel-spun backing over Dacron backing. The same reel can hold up to 75% more gel-spun line than Dacron line. If you’re fly fishing on the open ocean, you will know that game fish can swim huge distances at fast speeds, and having more than double the amount of backing line can help you play these fish out and reel them in.

Gel Spun is often also referred to as PE Backing (hence the HMPE), or Spectra backing. There are some small differences explained below.


Dacron Vs Gel-Spun Backing

Each of these types has advantages and disadvantages. Gel-spun is smaller in diameter, but it can cut your fingers pretty badly. It has less stretch than Dacron, which can be a good thing or a bad thing depending on your needs. Both of these types are very strong and hold up in the elements, although gel-spun is a little more UV resistant. Neither of them break down easily, which means that you absolutely must carry them out with you to protect the environment after you’re done fishing.

If you don’t want to use Dacron or gel-spun, you have other options. One of these is Micron, which is a Dacron-based alternative. Micron braids Dacron strands into a tight, round braid that is stronger and less prone to tangling than flat braids. The other alternative is Hatch’s PE braided backing (or see on Trident Fly Fishing). It combines the touch and feel of Dacron with the strength and reduced diameter of gel spun, but won’t cut your fingers as easily as gel spun does. It’s a bit more expensive, but many anglers do feel that it’s worth it.


How Much Backing Do You Need?

Backing comes in spools of much greater lengths than you’ll see available for fly line. Backing spools are available in lengths from 50 yards to 1000 yards or more. Suffice it to say, if you’re buying a 1000 yard spool, you won’t be needing all of that length for one reel! Instead, you’ll load what you need onto your reel, saving the rest for later. New anglers setting up their first reel need to remember to not add so much backing that the fly line and the backing fill up the entire reel and cause friction. A small arbor (small diameter) fly reel will only be able to handle so much backing with the fly line.

The length of your backing depends on the fish you’re trying to reel in, and the size of your fly reel. As mentioned earlier, you won’t need much backing line if you’re only going for panfish or small brook trout. Most trout fishing requires about 50 yards of 20-pound backing. Anglers who go after steelhead or salmon usually prefer to use significantly more than this, about 175 yards of 20-30-pound backing. If you’re fishing for salmon in streams with a strong current, you may want to bump this up to 250 yards.

Some game species, however, like bonefish, tarpon, and permit— all marine fish— have more room to run. For these fish, you’ll want at least 200 to 250 yards (or even more) of 30-pound backing. If you want to fish for sailfish, marlin, or other big open ocean gamefish, you will need a lot of backing— between 500 and 700 yards, just to be safe. You’ll also want to use backing specially designed for fish of this size; 65-pound test backing is available for reeling in these oceanic giants.


Saltwater Vs. Freshwater Backing Choices

While most people think of fly fishing as a freshwater endeavor, it’s just as fun to go fly fishing in saltwater! A huge variety of saltwater fish can be caught through the fly fishing method, but fishing on an ocean or estuary is very different from fishing on a river. It’s not just the salinity of the water being tougher on your equipment, or that the fish have different eating patterns and different insects available— the size of the water is a major factor in how you have to change up your fishing technique to go from the river or lake to the ocean.

Both Dacron and gel-spun backing perform just fine in saltwater. The deciding factor isn’t necessarily the performance of the material. On saltwater, you’ll find one of the key differences is your backing length. The leader, tippet, and fly line can be the same length, but on the open ocean, you’ve got more room to fish and can drift longer. This means that you will want to use way more backing, which is why gel-spun backing is so popular with saltwater fly fishers, as its small diameter means you can load more onto your reel.


Backing Alternatives

Can you use other line as fly line backing? If you are in a pinch, absolutely. You can use monofilament line, braided line, or just about anything if you need to quickly rig your reel. While this isn’t ideal, it certainly will work!


Does Backing Color Matter?

The color of backing only matters for looks! If you have a reel with some open space on the side, your backing and fly line becomes visible. This means that different color backing will give your reel a different look. Pick any color you want!


How To Tie Backing

You have to tie backing twice: once on the reel and once to the end of your fly line. When you attach your backing line to the reel, it’s tied directly to the arbor of the reel. The arbor of the reel is the center of the spool. Usually, fly fishers use an arbor knot to tie on the backing. This knot is a couple of overhand knots tied into a slipknot and does a good job of keeping the backing on the reel.

To tie this knot, the first thing you do is wrap the backing line around the arbor. Then, take the end of your line and form a loop around the long part of the line. You’ll then pass the tag end (in this case, the short end) through that loop. Tighten the knot— this is your slipknot. Then, you need to tie a knot in the short end. You’ll loop that end around itself and tighten it, creating a knot at the end of the line. Pull the long end of the line away from the arbor until the two knots are jammed tightly together, and your line will be secured!

For tying the backing to the fly line, you have several options. While pretty much everyone uses the arbor knot to attach the backing to the reel, the knot you use to tie your backing to your fly line is based on personal preference. We’ve given instructions for the two most popular here, the nail knot and the Albright knot, but you can also use a triple surgeon’s knot, a loop to loop knot, blood knot, double uni knot, double double uni knot, a J knot, or other strong line-to-line knots.

Below we have included videos to help you along the way.

Video For Tying Fly Line To Backing:

Tying Backing To The Reel:


Nail Knot

The nail knot uses a nail or other cylindrical object (a coffee stirrer works great) to help tie the two pieces of line together. This line is easiest to complete when your object is a hollow tube, which is why a coffee stirrer works so well. This knot is also a popular one for attaching the fly line to the leader at the other end of your line!

To tie a nail knot, lay a nail, coffee stirrer, or another small tube against the end of the fly line. Set your backing line against the line and cylinder. Leave an extra 10-12 inches of its tag end (the end not connected to the reel) to tie the knot. Working left to right, make 6-8 close together wraps with the tag end of the backing line around the fly line, backing line, and cylinder. back around the leader, line, and tube or nail.

If you have a nail, you need to remove it now so that you can pass the tag end through the space made by the nail. If you’re using a tube, you can slide the tag end through the tube and then remove the tube after the line is through. Then, all you have to do is pull the tag end to tighten the coils, and then tug on the backing line and fly line to seat the knot firmly. Trim the tag end of the backing line and you’re done!


Albright Knot

The Albright knot is a strong line-to-line knot that doesn’t require a nail. It’s slightly more complicated and takes longer to tie than the nail knot. However, this knot is prized for its security once completed, and many fly fishers like using it to attach their backing to their fly line.

To tie this knot, start by unwinding 2-3 feet of fly line. Make sure you use the end marked ‘this end to reel’! Double back a couple of inches of this line to make a loop, and hold the loop in your left thumb and forefinger. From the right, slide in about 10 inches of the backing line through the fly line loop. While holding the loop, pinch the backing between your left thumb and forefinger, and use your right hand to wrap the backing tag end (in this case, the end not connected to the reel) back over both strands of the fly line and the backing. Work towards the loop end and make 8-12 fairly tight wraps. Then, push the tag end of the backing back through the loop on the side opposite where it originally entered. You’ll see both backing strands exit on the same side of the loop. Pull on the long part of the backing to tighten the loop you were holding in your left hand, and once that’s tight, pull both ends of the fly line backing.

Once you’ve tightened the backing loop, you need to finish the knot on the fly loop side. Gently pull on both ends of the fly line loop with your left hand and squeeze the knot with the fingers of your right hand to work it down to the loop end, but not off the fly line. Moisten the knot using water (or saliva) to help tighten it. Hold both the tag end and long strand of fly line in your left hand, and the tag and long strand of backing line in your right hand. Pull as tight as possible. Trim the ends, and you’re done!


Extra Security

Some anglers like to finish their knots with a little bit of superglue to help hold things in place. While superglue alone will not hold a bad knot, it can help strengthen a good knot. You can use regular superglue, or if you want something even stronger, you can use a UV-cured glue like Knot Sense (See On Amazon). The advantage to a product like Knot Sense is that it dries instantly and is more pliable than superglue. Some anglers also like to coat their knot with waterproof rubber cement so that it runs through the eyelets more easily.


Final Thoughts

Backing line is an important part of your fly tackle. It’s your insurance policy against fast, powerful fish getting away. Like all other types of line used in fly fishing, you have options. Backing line isn’t a one size fits all piece of gear; your backing needs are unique to how you fish. We hope that our guide has shown you everything you need to make the best backing decision.

Max DesMarais

Max DesMarais

Max DesMarais is the founder of hikingandfishing.com. He has a passion for the outdoors and making outdoor education and adventure more accessible. Max is a published author for various outdoor adventure, travel, and marketing websites. He is an experienced hiker, backpacker, fly fisherman, backcountry skier, trail runner, and spends his free time in the outdoors. These adventures allow him to test gear, learn new skills, and experience new places so that he can educate others. Max grew up hiking all around New Hampshire and New England. He became obsessed with the New Hampshire mountains, and the NH 48, where he guided hikes and trail runs in the White Mountains. Since moving out west, Max has continued climbed all of the Colorado 14ers, is always testing gear, learning skills, gaining experience, and building his endurance for outdoor sports. You can read more about his experience here: hikingandfishing/about