Hatch coaming drains are still proving to be one of the major sources of ingress of water into a vessel's holds, and over which there can be virtually no heavy weather defence if they are either missing or defective in some way.
Usually fitted at the aft two corners of the hatch coamings, the drains are basically provided to allow water that manages to pass through the hatch cover sealing gasket, to run aft, along the coaming channels, and drain from the channel to the vessel's deck rather than entering the cargo hold below. Seas breaking on a vessel's decks however, frequently reach the height of the hatch coaming, and unless some means is provided to close the drain, water will pass up the drain, fill the channel and from there pass to the cargo hold below. On large vessels, there may also be drains fitted at the forward ends of the coamings in additional to those aft.
Lloyds Rules 2002 specify
4.2.9 Drain openings are to be arranged at the ends of drain channels and are to be provided with effective means for preventing ingress of water from outside.
(c) Where the drains are not provided with an approved automatic means of preventing water entering the hold, the drains are to be capable of being closed by a screw plug or cap which is to be attached by a strong keep chain to the drain.
By way of comparison, Bureau Veritas 2002 specify
8.1.2 Drain openings are to be arranged at the ends of drain channels and are to be provided with efficient means for preventing ingress of water from outside, such as non-return valves or equivalent.
All too frequently, the condition and maintenance of drain valves are overlooked by those on board, and in many cases, also by surveyors who may be carrying out hose or ultrasound tests of the hatch covers themselves.
Whilst Classification Rules on the subject may be open to some interpretation, as can be seen from the extracts provided as an example above, short lengths of canvas hose attached to the drains are notusually accepted as being either "non-return valves or equivalent" , or as being an "approved automatic means". Whilst it remains a mute point as to whether a length of canvas hose in good condition provides either an "efficient" or "effective" means of preventing water ingress, in the case of the Lloyds requirement, such hoses cannot be closed by a screw cap and therefore do not meet the requirements in any case.