Safety Tether

What is a Safety Tether?

Your harness should have a safety tether attached to it.  The most basic use for a safety tether is to allow the user to quickly tie into an anchor point when in a precarious position.  The safety tether is connected to something secure to protect from a fall if you should slip or be pulled over a drop. 

A tether can be set up to allow the canyoneer to rig rappels, assist others while protecting themselves from a fall, adding back up to a suspect anchor or many other uses.  While the primary use for a safety tether is to tie off to something secure, they have other uses as well.  Safety tethers can help with ascending, hanging a pack while rappelling or high stemming, passing knots and various rescue techniques.

Why is an Adjustable Tether Good?

An adjustable tether is desirable to allow the length to be set for the given situation.  For safety it is best to have little to no slack in the safety tether when in use.  Trying to work on anchor rigging or assist other canyoneers generally requires some mobility.  So it becomes common to leave a little slack in your safety tether (which should be kept to bare minimum) to allow a little room for movement.

It is very important to keep slack out of the system when using safety tethers.  This applies to all safety tethers but is especially important when slings are used since they are very limited in length adjustment.

Very short falls can produce enough force to cause a sling to fail or push other gear to its breaking point.  If the tether does not fail, there can be enough force generated to cause severe injury to the canyoneer.  Sure you may live if you fall hard but hanging over a ledge with a broken back does not sound like a good time to me.

DMM Climbing did a test on nylon and dyneema slings titled "How to Break Nylon and Dyneema Slings".  After watching the video you will likely want very little to no slack when using slings (or any other tether) as fall protection.

The test is very enlightening and the video gives a much better understanding of what they are doing.  Rather you use slings or something else as your safety tether, it is a good idea to watch this video.  You may be surprised at what you learn.

One of the notes on the DMM web page notes that forces above 10kN begin to cause internal injuries.  A fall of just 60cm (close to 2 feet) with an 80kg mass (about 176 pounds) can generate 16.7kN of force.  Think about that for a minute, an average size man dropping only 2 feet can possibly generate enough force to seriously hurt you (if the gear doesn't fail first). 

If you are an experienced canyoneer, think back and see if you can remember times when you left 2 feet or more of slack in your tether while at the top of a drop.  It is very easy to leave a lot of slack so you feel free while in the back of your mind you think you're ok since its only a fall of a few feet if you slip. Before learning how much force can be generated from a short fall, I know I have been guilty of this.

Tying an overhand knot in the middle of the sling reduced the breaking strength form the rated 22kN down to about 10 or 12kN.  So tying a knot into a sling to shorten it can reduce its breaking strength to less than what a 2 foot fall can generate.  2 feet of slack is not very much and is common for canyoneers to set more than this to allow movement.  Taking a 2 foot fall on a sling or any safety tether can generated enough force to cause internal injuries.  But if using a sling with a knot tied in it, the sling may break letting you fall.

What are the Common types of Tethers?

Purcell Prusik - The Winner!
Purcell Prusik is an adjustable tether option with some other advantages as well and is a good choice for a safety tether.

The Purcell Prusik also absorbs some of the force when shock loaded.  When the prusik is shock loaded it will slip a few inches then grab.  The slipping helps absorb some of the force.  This helps reduce the force placed on the human body and gear.

The Purcell Prusik is cheap, adjustable in any increment, can be lengthened under load, can be used as an ascender in a pinch.

Since the Purcell Prusik can also be lengthened under load it can be versitile.  A useful situation for this might be to clip into the anchor with the tether then set up the rappel device.  You can then lengthen the tether until the rap device is weighted and check that you are rigged correctly before unclipping the tether.  Great for helping new people feel confident.

For information on how to size and tie your own purcell tether, check out the How to make a Purcell Prusik for a Safety Tether page.

Anchor Chains - Safe option to a Daisy Chain
Anchor Chains are a safer alternative to the daisy chain.  An anchor chain is a series of individual loops of webbing linked together like a chain.  Since they are individual loops not separated by stitching like a daisy chain, each loop is rated to full strength and can be used at any time by clipping into it.

Metolius makes one of the more popular anchor chains called the PAS (Personal Anchor System).

If you like using a daisy chain for canyoneering, a much safer alternative is an anchor chain.  Of course you still want to keep as much slack out of the system as possible when clipped in.  Even short falls can create large harmful forces on gear or the body.

Anchor chains are rated to full strength at any point and can be adjusted in preset increments.  An undesirable aspect is the clutter of webbing rings attached to the harness while not in use.  These can catch on trees, logs, rocks and many other things as you make your way down canyon and should be kept in mind while wearing one (especially in water).

Slings - Not Recommended
Slings are one of the basic options.  Simply girth hitch a sling to your harness and you have a safety tether.  Adjusting the length of a sling is simple but can only be done in large increments.  To adjust length you need to use a different size sling or twist the sling to achieve a half sized double loop.  In some cases this works well but in other cases it is easy to leave too much slack in the system, possibly setting the canyoneer up for a painful or deadly fall.  Care needs to be taken when using slings by keeping the slack to a bare minimum (preferably less than a foot of slack).

Since it is difficult to get small increments of adjustment from slings they are not recommended as a safety tether but can be used if caution is exercised.  Slings are very useful for other tasks but not recommended for a safety tether.

Also of note, spectra slings are lighter, more abrasion resistant and more UV resistant.  While the Nylon slings are bulkier they have more stretch allowing them to dissipate some of the shock like a dynamic rope.  Both Dynema and Nylon have different advantages.  It is a good idea to be aware of them as you make decisions.

Petzl Spelergyca
The Petzl Spelergyca is another option for a safety tether.  The Petzl Spelergyca is actually two tethers of unequal length 32cm and 58cm (12 inches and 23 inches).  There are a lot of uses for these due to the two unequal length tethers.  The same thing can be accomplished with a 1 foot and a 2 foot sling or any other type of tether.

The Spelergyca is adjustable by selecting one of the tethers.  They are adjustable but you have just two lengths to choose from.  Some people have suggested tying knots in these to shorten them further.  Keep in mind that doing so can significantly reduce the strength of the tether just as a sling strength is reduced from knots.

Daisy Chains - Do Not Use!
Daisy Chains should not be used for Canyoneering.  Daisy chains can prove deadly if used improperly and its easy to do.

It is desirable to have an adjustable length tether but daisy chains are not designed for use as a direct tie to an anchor, which is one of the primary uses of a safety tether while canyoneering.  There are safer ways to achieve an adjustable safety tether.

Daisy chains were designed primarily for aid climbing where the rope is "in" the system.  A daisy chain is not intended to be used as a tie in to an anchor unless the rope is part of the system.  Climbing ropes are dynamic and stretch in order to absorb some of the shock when a fall occurs.  The shock absorbing qualities take some of the force off of other gear in the system like the daisy chain.  Check out this page from Black Diamond about Daisy Chain Dangers

The daisy chain is strongest from end loop to end loop.  The individual loops along the daisy chain are only rated for body weight and only in a static situation where the loop will not be shock loaded.  Since the common use in canyoneering would be to clip into an anchor while you work on the rigging, there will be some slack left in the daisy to allow mobility.  If the canyoneer falls while anchored in, the slack will allow a short fall and the safety tether will be shock loaded.  Daisy chains are not designed to hold up under these conditions.

If you currently use a daisy chain as your safety tether, it is likely that you have a carabiner in the end loop clipped into the anchor point.  When you need a shorter length, you simply clip one of the intermediate loops into the end carabiner now having two loops in the carabiner at the anchor.  This is a potentially deadly situation!  Do not do this.  If you take a fall, the intermediate loop is likely to fail since it is not rated for a shock load.  When it does fail you will likely be clipped to nothing!  It is possible that being clipped to two loops can result in just being clipped around the tack of stitching in the daisy chain.  This is extremely difficult to explain in written form.  Take a look at the Daisy Chain Dangers page again and scroll down a little over half way down to the video showing what can happen.  Watch the video.  This is pretty scary since it would be so easy for this to happen.  If you still insist on using a daisy chain, do not shorten it by just clipping in an intermediate loop to the same carabiner.  Use a second carabiner on the loop and clip it to the first carabiner.

 Bottom line...... Do Not Use A Daisy Chain for Canyoneering.