Sumps and existing lines

||Sumps and existing lines

Whether a new project or a training/tourist dive you will most likely be diving on a line that is already present. This comes with a few advisories.

  1. Is it a long time since the sump has been dived?

(this can be hard to determine – consulting the CDG N/L can be a good start as contacting others known to have dived there).

  1. Type of sump:
    1. High flow or low flow?
    2. Is it a muddy, smooth-walled sump or lots of rocks and sharp edges?
    3. A mixture of types…

This can give an idea of what the lines condition might be – some sumps have notorious abrasion points where the line frequently breaks (e.g. lip a shaft) or becomes buried in silt (e.g. at corners).

  1. Type of line used:
    1. Polypropylene (floats)
    2. Nylon(sinks)
    3. Other material (floats or sinks!)
    4. Size 4mm or 6mm
    5. 12mm (climbing rope)
    6. Wire
    7. Something else? Caving belts!

Type of line can mean some thought on the cutting implement required, (some sumps were/are lined with coated wire). Also where the line is likely to be: in the roof or under a layer of silt. They type of line can also affect its ability to hold a knot e.g. Kevlar coated line is very slippery. In most UK sumps polypropylene is the preferred material – try to avoid any type of coated line (e.g. “Glowline”).

  1. Before undertaking a project beyond a sump or sumps the best advice is to check the line.
    1. If it is in reasonable condition then check the belays, reposition or add new ones.
    2. If you have doubts on the condition then reline the sump.

This may seem an extra task when you want to just get on and dive but it is important. Line laid in the sump for the purpose of initial exploration may not always follow the most convenient route as the explorer might have been diving in poor visibility or navigating by following one wall of the passage. If the site is likely to receive more traffic, more optimal line placement might be required and they may not be sufficient slack in the existing line to do it.


  1. Lay a well marked (distance and in and out marks near to the existing line)
  2. Remember the extra hazard of the existing line near to you during the relining phase
  3. Carefully remove the old line
  4. A number of methods can be used to remove old line:
    1. Spool it on to an empty line reel.
    2. Stuff it into a tackle bag.
    3. Spool it on to a length of tube.
    4. In some cases the line can be cut into 1 m lengths and left – although it is better to remove old line.
    5. Simply wrapping it around your person usually ends badly!

Yellow out Twin cable ties out (good in zero visibility)

Two cable ties – green with short tail = OUT, red with long tail = IN plus distance marker in metres.


Duck Tape tag, cut obliquely to point way OUT with number (= multiple of 5 m) plus permanent cable tie threaded through lay of line.

Where the line is tied to the reel a long loop is left to tie on the next line by larksfooting a corresponding loop on the end of the next line (plus reel) through it. The short tail to the reel can be cut away.

Repairing line.

Sometimes the existing line can be in generally good condition but small sections in high wear areas could be damaged or broken.

Note: Do not put undue stress on the line when working on a repair as this may cause another break.

  1. If you have good solid belays then you can reline the damaged area belay to belay (remove old line).
  2. In some area a small repair maybe needed.
  3. If you have line with you (not search reel line as this is to thin) you can remove the damaged area and put a knot into each end and add new line between the knots being careful to keep in contact with the “out” line.
  4. Temporary repair
    1. If you do not have line with you of the correct size then a search reel line can be used to make the repair being aware that using too much of the search reel (line)could compromise its deployment if required later in the dive
    2. Snoopy loops can be used to affect a temporary repair looping a number together and fixing to the broken ends with cable ties or knots.
    3. If the lines can be ovevr lapped then cable ties can be used to join the line together a knot will stop it pulling through the cable ties.

Snoopy repair

Close up of knot

Search reel line repair

Knot detail (over hand knot on the search reel line)

Knot repair

Knot repair with cable Ties and stopper knots for extra security.

Cable tie repair this is used if extra line is not available and not enough from each broken end to knot together a temporary and somewhat risky repair.*

Section of new line used to repair a missing section.

* It has a risk of pulling through (stopper knots are a possibility). A loop can be tied in each end of the broken line and cable tied together although if you have enough line to do this then just tie the line together.

With a broken line on route in then you have time to locate the other end to affect a repair. If the break occurs on route out then it is more of a problem. If you have come from an air space you can always retreat to regroup. If that is not an option then time is against you in either case the search reel will need to be used (unless you have a larger reel with you).

If a temporary repair is made a few other points,

  1. If other divers are following and you are on route back you should if gas, vis and passage dimensions allow wait to indicate the repair.
  2. Within a short time the line should be revisited and a full repair or relining should be undertaken.

iii. Mark the line at dive base as broken with a temporary repair.

The notes (above) are designed to be used with a Welsh section training sessions. Techniques and knots can be shown with more clarity during training sessions.

© AMW/DMP 31/08/12