Understanding Fly Fishing Lines: Tapers, Sink Rates & Weight Explained
Updated: Sep 21
Kingfisher Trouts Lakes where we camp alot
Fly Lines Quick Summary
I got into fly fishing because of my grandad. When he passed away he left me all his old gear, cane Hardy rods and reels, boxes of old flies, and an old Bradley trout bag made in Halesowen just outside Birmingham. I actually tried fishing with his old gear once, and it was an eye opener seeing how much things have developed over the years.
I used to buy my own kit from a shop called Powell in the centre of Birmingham, mainly a gun shop but with a decent fly fishing section tucked away, long since shut down like a lot of places like that. It's mostly all online now. Orvis have closed nearly every shop they had bar the one in Hampshire, which is a shame because I really liked those shops, though Farlows in London and Sportfish are both still going strong and are two of my favourites.
Anyway, onto lines themselves, this is the guide I wish someone had just handed me years ago rather than working it out myself, the sink rates, the tapers, and the bit almost nobody actually tells you about the number on the box.
A Bit About Where I Started
I'm no expert when it comes to fly fishing, far from it, I'm a casual angler who's picked things up over the years rather than studied them properly. For a long time floating line was pretty much all I used, just in different weights depending on the rod and the water. I've tried most of the big brands along the way, never really got on with Orvis lines if I'm honest, Rio's been really solid, Scientific Anglers too, and at the moment the floating lines on my reels are all Airflo and Sunray. Casting's never been my strongest suit, so I look for a line that'll get some distance without needing perfect technique behind it.
The last few years I've started using more sinking and intermediate lines too, rather than sticking to just a floater, mainly to start catching fish at different depths instead of only whatever's near the surface. Airflo's Di range is what got me into that, and I think they're excellent lines for the money. What follows is just the basics of what I've picked up pulling all that together, not a masterclass, just what actually mattered to me buying a line.
Worth saying as well, I've dug through a fair bit of technical detail to pull this together properly, since a lot of it isn't stuff you just pick up from fishing, it's worth explaining clearly rather than assuming everyone already knows it. I've tried to explain it as simply as possible rather than drowning it in jargon.
Top Fly Lines by Price
Top of the range (£100+):
Rio Elite Gold – Around £129.99 (Farlows/Sportfish), their SlickCast coating is one of the slickest shoots on the market, and it's built to outlast far cheaper lines
Scientific Anglers Amplitude MPX – Around £109 (Orvis UK), the AST Plus coating and half-size heavy taper make it a favourite for loading fast action rods with minimal effort
Airflo Superflo Ridge 2.0 – around £130, Airflo's flagship floating taper, well regarded among UK stillwater regulars
Guideline Bullet+ – Around £110 to £130, a Scandinavian brand known for smooth loading and low stretch cores, popular with anglers who want something a bit different
to the usual big names
Mid-range (£55 to £85):
Airflo Sixth Sense Di3/Di5 – Around £59.99 to £69.99, this is the range I run myself, proper competition-grade sinking lines without the premium price tag
Snowbee XS Plus – Around £55 to £70, a long-time UK favourite, used by casting coaches and competition anglers alike
Cortland 444 – Around £60.99 to £65.99, a genuine classic that's been around for decades and still holds up well against newer lines
Orvis Clearwater – Around £55.00, a solid budget-friendly option from Orvis, though it's never been my personal favourite
Sunray Kevlar NoKnot Proline Floating – £62.99, the other line I actually use myself for max distance, though the one thing I'd say is the quality on some of these lines isn't the best, they don't tend to last very long
Budget (under £40):
Leeda Profil – Around £19.99, covers floating, intermediate and sinking in the same affordable range, a genuinely sensible starting point
Finner Fly Lines – £9.99 (currently reduced from £27.99), Sunray's budget sub-brand, covering the same floating and sinking range across the board at one flat sale price
Greys Platinum Floating WF – Around £29.99, a reliable budget floater from a well known name in UK tackle
Wychwood Connect Series 2 – Around £39.99, low memory and a soft core that helps reduce hook pulls, decent step up while still staying cheap
Why Fly Line Weight Doesn't Mean What You Think
Here's the thing nobody tells you when you're starting out, that number on the line, the 5, the 6, the 7, used to actually mean something exact. Back in the 1960s the industry set a standard so a 5 weight line weighed roughly what every other 5 weight line weighed, simple as that.
Except most manufacturers don't really bother sticking to it anymore. Modern rods are stiffer than the old bamboo and fibreglass ones the standard was built around, so line companies have quietly crept the weights up over the years to make them load properly. Buy a 5 weight from one of the bigger brands today and there's a fair chance it's actually closer to what used to be a 6, sometimes even a 7. I've seen UK anglers going round in circles over this exact thing on forums for years, buying a 6 weight line for a 6 weight rod and wondering why it casts nothing like it should, only to find out later the line's a full weight heavier than the box claims.
Not really anyone's fault as such, just the industry moving faster than the labelling ever did. But it explains a lot of the confusion out there, and it's genuinely one of those things I wish I'd known years ago. If a line ever feels off on a rod that should suit it, don't assume it's you, the label might just be lying.
There's also a difference between a line running heavy by accident and doing it on purpose. Plenty of anglers deliberately go up a line weight or even two, putting a 7 weight line on a 6 weight rod, because it loads the rod faster and helps you get distance without needing a perfect cast to do it. That's actually one of the reasons I've ended up gravitating towards it myself, since casting's never been my strongest suit.
Floating, Intermediate & Sinking Lines
A floating line sits on top of the water, and it's the one I'd tell anyone to buy first. Dry flies, nymphs under an indicator, buzzers fished static, it all works off a floater, and it's what I stuck to myself for years before I ever branched out.
Intermediate lines sink slowly and evenly, somewhere around half an inch to an inch and a half a second depending on the brand. This is the one to reach for once trout are cruising just under the surface rather than sat right on top or holding deep, which on a lot of the UK stillwaters we fish happens more than people expect.
Then you've got full sinking lines, a completely different job, getting a fly down fast and keeping it there. These are the Di lines, and they're worth actually understanding rather than just grabbing whichever one's cheapest on the shelf, which is more or less what I did the first time round.
Understanding Di Fly Lines: Di3, Di5 & Di7
Di stands for Density Intensified, which really just means dense enough to sink quickly. The number after it is the sink rate in inches per second, so a Di3 drops at roughly 3 inches a second, a Di5 around 5, and a Di7 around 7. Airflo's Sixth Sense range is probably the best known set of these over here, though Rio and Cortland both do their own take on it.
The number matters more than people give it credit for. A Di3 settles in the upper part of the water column and suits a slower retrieve, good for cruising fish or shallower stillwaters. A Di5 gets down quicker and holds in the middle depths, handy on a windy day when a slower line just won't punch through. A Di7's for when the fish are sat low and you need to get there fast, a direct line with barely any belly to it.
Working out how deep your line's actually fishing comes down to fairly simple maths, sink rate times however many seconds you let it settle before you start the retrieve. Wind, current, and the weight of the fly all knock that about a bit, but it's still a far better starting point than just guessing and hoping, which was pretty much my approach before I understood any of this. I've been running Airflo's Di range for a few years now and it's changed how many fish I actually catch, moving past just fishing a floater and starting to work different depths properly.
Weight Forward or Double Taper
Weight forward lines carry more weight up front, which loads the rod quickly and makes casting easier, especially into wind or when there's distance to cover. It's the standard choice for most UK stillwater fishing, and given my own casting isn't the best, this is pretty much all I've ever fished with, since it does a lot of the work for you rather than the other way round.
Double taper lines are the same taper at both ends, which makes them better for delicate presentations at shorter range, dry fly fishing on smaller rivers being the obvious one. The other advantage is you can flip the line round once one end wears out, effectively doubling how long it lasts, something a weight forward line just can't do.
What UK Stillwater Anglers Actually Run
Competitive loch style anglers over here tend to carry a small handful of lines rather than one that does everything, a floater for buzzers and washing line tactics, an intermediate for cruising fish, and a Di3 or Di5 for deeper water or fighting through wind. It's less about owning the priciest line on the market and more about having the right density on the reel for whatever the day throws at you, which is really the same approach I've ended up with myself without ever setting out to copy anyone.
My Advice If You're Just Starting Out
Every line's different, and a lot of it just comes down to personal choice in the end. Don't be afraid to ask people for help, either online or in the shops I mentioned earlier, Sportfish, Farlows and Essential Fly are where I buy most of my own stuff from these days.
If you're only just starting out I'd just go with a floating line to begin with. You can still get down a bit by changing your tippet length and using heavier flies or lures to help it sink, or just switch to a dry fly if you want to stay on top. No need to overthink it or buy three different lines before you've even had a proper go.
Looking After Your Fly Line
Fly line isn't cheap, so a bit of care goes a long way. Clean it every few outings, a bucket of lukewarm water and a mild soap's all it needs, pulled through a soft cloth to lift off the dirt and algae that builds up and drags on your casting over time. Keep it out of direct sun when it's not in use since UV breaks the coating down, and try not to stand on it, wading boot cleats will saw through the surface faster than almost anything else you could do to it. Store it in loose coils rather than wound tight too, a line left coiled up tight for months is exactly what gives you that annoying memory where it won't lie straight on the water.
FAQ
What does IPS mean on a fly line?
IPS stands for inches per second, the rate a sinking line drops through the water. A Di5 line sinks at roughly 5 inches per second.
Is a 5 weight line always 5 weight ?
Not necessarily. Plenty of modern lines run heavier than the official standard for that weight, so a labelled 5 weight can behave closer to a 6 or 7 weight once it's on the rod.
What's the best all round fly line for a beginner?
A weight forward floating line covers the widest range of UK stillwater and river fishing, and it's where most of us at FFF would point anyone starting out.
How often should I clean my fly line?
Roughly every 3 to 5 outings in freshwater, or after every trip if you're fishing somewhere muddy or weedy.
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Thanks James | Fishing Field Fork
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