Trout eat mostly below the surface so your fly fishing set up must be able to reach these depths. Enter sinking fly lines.

Understanding the Basics of Sinking Fly Line

A sinking fly line is used to fish nymphs and streamers. Since most of the trout’s diet is consumed below the surface it just makes sense to have either a sinking fly line on an extra spool or a mini-sink-tip section that can be added to the end of your floating line.

Nymphing Guide Streamers Guide

How does sinking fly line work?

The sinking section of a fly line has powdered tungsten in the coating, which causes it to sink. The amount of tungsten added to the coating will vary depending on the sink rate desired.

The sink rate is the distance the line sinks per second. Tungsten is used instead of lead because it is more environmentally friendly.

Can I use split shot?

If you tried to add heavy split shot to your leader instead of using a sinking line you would have a harder time controlling your cast.

Below we'll look at the different sinking fly lines that are made today and when you would use them.

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Sink-Tip Fly Lines (Labeled as F/S)

A sink-tip fly line is a line that is about 90 feet long. The first 10 to 30 feet is the sinking section; the balance is a floating line. It is the most common line used today for fishing nymph and streamers.

The floating section has small micro balloons added to its coating to help it float.

The floating section allows you to control the line better with a flip of the rod tip (a mend). It is also easier to cast and is easier to pick up off the surface. The sink section comes in different sink rates and lengths.

An extra spool for your reel becomes necessary with these so you can change lines when needed.

Mini Sink-Tip Fly Lines

Mini-sink-tip lines are from 10 to 15 feet long and are added to the end of a floating line.

They have different sink rates. These are also easier to cast, and becoming very popular because they can be added to the end of a floating line. Like the sink-tip line they are easier to cast and control. Another benefit of this system is you do not have to carry extra spools of lines with different sink rates.

I love my MOW sink-tip kit from Rio. I use this set with my Skagit head when fly fishing for steelhead trout. This is a set of removable sinking tips that I add to the floating line.
You can change out the end depending on the conditions. This is a very helpful feature when fly fishing a river where you may come upon a deep pool or faster water.

Full Sinking Lines (S)

Full sinking fly lines have no floating sections whatsoever. This makes them harder to cast, especially the faster sinking lines. They sink at a uniform rate.
It is harder to mend the line and get a good natural drift with these lines.

Intermediate full sinking lines (I) sink slower and are designed for fishing just below the surface. This is nice when you are fishing a lake that has a lot of weeds or when fishing close to shore. These lines sink from 1/2 to 1-1/2 inches per second.

The other full sinking fly lines are divided up into Slow, Fast and Very Fast sinking rates. The faster sinking lines are designed to fish fast water, deep pools and deep lakes.
They are also used when trolled behind a small boat or float tube.

Different manufacturers will label the sink rate differently (Type V instead of 1, 2, 3) but all will have the sink rate per second on the box.

  • Sink Rate

    Sink Rate in Seconds

  • 1 (Intermediate)

    1/2 to 1-1/2″

  • 2 (Slow)

    1-1/2 to   2-1/2″

  • 3

    2-1/2 to   3-1/2″

  • 4

    3-1/2 to   4-1/2″

  • 5 (Fast)

    4-1/2 to 5-1/2″

  • 6

    5-1/2 to 6-1/2″

  • 7

    6-1/2 to 7-1/2″

  • 8 (Very Fast)

    7-1/2 to 8-1/2″

  • 9

    8-1/2 to 9-1/2″

  • 10

    9-1/2 to 10-1/2″


When fly fishing for trout what is the best fly line to get?

It depends (I love that answer). For your first line, you need to get a floating line (a double taper or weight forward). If fishing rivers, a mini-sink-tip kit or a sink-tip line on an extra spool is a very good idea.

Make sure you have everything you need

The possibilities for rod, reel, line and leader combinations are endless. Show up to the river prepared by reading our guides, and stocking up on insect specific, curated fly boxes.