Sinking Line: Which Line to Buy?

I have found that there is considerable confusion among the angling community regarding sinking lines and grain weights. When choosing a floating line, one only needs to worry about the weight of the line. When choosing a sinking line, there are two things to consider. The first is the grain weight, the second is the density.

A rod is an interesting tool which in order to work, must be loaded. We use the weight of the line to load the rod, and then the rod unloads sending the line on its way. Each rod loads or bends at a different location which determines its action. But the stiffness of the rod will determine how much weight it takes to load it. Each rod is rated in accordance with a set of standards established by the American Fishing Tackle Manufacturers Assoc. A rod that is properly loaded with 120 grains would be classified as a 4 weight, one that is properly loaded with 210 grains would be classified an 8 weight and a rod that is properly loaded with 380 grains would be a 12 weight.

A given rod will always load with the same amount of weight and this will not change. If a given 8 weight rod properly loads with 210 grains, and we put a line on it weighing 200 grains, it will be under loaded. A 200 grain line falls short of the acceptable tolerances for an 8 weight (202-218 grains). The same line will overload a 7 weight rod that is properly loaded with 185 grains. The acceptable tolerances of a 7 weight line would be from 177-193 grains. So the 200 grain line would neither fit a 7 or an 8 weight rod. Obviously some 7 weight rods handle 8 weight lines and vice versa. This is also assuming that you are casting 30 feet of the line, which is the measured portion.

When it comes to floating lines, we almost never worry about grain weight. We know which line weight we like to throw on each of our rods and we always buy that weight, even if it is 1 weight heavier or lighter than our rod designates. But when line manufacturers market sinking lines in a variety of grain weights, it causes all sorts of confusion. For example: Jim Teeny markets a saltwater line, the TS550 which he recommends for a 9,10,11,12 or 13 weight rod. And Scientific Anglers’ 850 grain deepwater express line will obviously overload a 9 weight rod which was designed to be loaded with only 240 grains. An 850 grain line would fit a 21 weight rod just beautifully. The reason for this is that the Teeny lines as well as the deep water express were designed to be cut to fit. The density is constant along most of the line, and you cut the line to the length that gives you the proper weight for your rod.

If you have a 7 weight rod that seems to be properly loaded with 30 feet of a 7 weight floating line, you can be sure that it will cast well with a 7 weight 30′ sinking head because the grain weight will be the same. A 7 weight line doesn’t sink, or float because it weighs 185 grains. It weighs 185 grains so that it will properly load a 7 weight rod. It floats or sinks because of its density.

When selecting a sinking line you must first determine which line weight will load your rod properly, and then you must determine how fast you want it to sink. The sink rate of a line is determined by its density. The denser the line, the quicker it goes down. So if I wanted a head to load an eight weight rod and sink at a rate of 5 inches per second, I could buy a 30′ 8 weight shooting taper with a type 4 or 5 sink rate, i.e. ST8S type 4 (or 5 depending on manufacturer.) If I wanted to buy a head for the same rod with a sink rate of 2 inches per second, I would get a ST8S type 2.

All this confusion is caused by the way in which some fly lines are marketed. For some reason, somewhere along the way, someone decided that the heavier the line, the faster it will sink. This is simply not the case. Among lines of the same density, there is only a slight difference in sink rates from 1 line weight to the next. This is miniscule and is only due to the fact that there is less drag on the line that has a slightly smaller diameter.

Cut to fit fly lines, such as deep water express, is usually available in three grain weights. 550, 700 and 850, but there are others. The reason for this is that they all have different densities. The 550 grain deep water express line for example, sinks at 7.5 inches per second, the 700 sinks at 8.5 inches per second, and the 850 will sink at 9.5 inches per second. Each one of these should be cut to length to provide the proper weight necessary to load the rod on which it will be used.

Wow! Isn’t this all a mess? It seems worse than it really is. In short, if you know what weight of lines you like to throw on your 7 & 9 weight rods, then buy your sinking lines in those weights. The only thing you really need to decide is how quickly you want them to sink. If however, you don’t know for sure, which weight to use, then you can buy some cut-to-fit line of the sink rate you need, and cut it to fit. The advantage to buying cut-to-fit lines is that there will probably be enough line in one box to make a head for multiple rods. The cut-to-fit lines usually come with instructions.

At the risk of sounding redundant, the grain weight of a shooting head or sinking line should be no more or less than the amount of weight you would normally false cast with. If you know this weight, buy the appropriate commercial line in the desired sink rate. If you don’t, choose the sink rate, and buy a cut to fit line. It is easy to adjust it to the proper length.

Because of the multitude of rod actions and casting styles, I don’t think you could say that any one weight line or shooting head is the right or the wrong line for a given rod. The important thing to remember is that weight loads a rod. Density sinks a line.