Ballast holds can be used either to hold ballast or to carry cargo. When cargo is to be carried it is essential that the proper steps are taken to ensure that ballast water cannot be admitted to the hold by accident. This is usually achieved by bolting a watertight coverplate over the ballast suction in the hold and this may be reinforced in the engineroom or on deck by fitting a blank, padlocking a valve or posting a notice. Blanks or cover plates which were fitted to the bilge, to the CO₂ smothering lines and to the hatch coaming drains must be removed so that these systems can operate whilst cargo is being carried.

These processes may have to be done, hurriedly, in the loading port since the hold may have been used for ballast during the previous ballast voyage.

There is likely to be a conflict of interests between the requirements for cargo and ballast, particularly when low density cargoes are to be carried, filling all cargo spaces including the ballast hold. At such times it may be difficult to find time and opportunity to clean the ballast hold at the start of the ballast voyage, before the hold is ballasted. Where possible the hold should be washed or, failing that, swept. If a hold is ballasted without removal of sweepings as a result of pressure of time, problems with blocked suctions will almost certainly be met at the time of deballasting, when the hold may be urgently required for loading.

Before ballasting it is, of course, essential to remove any blanks or coverplates which have been fitted to ballast suctions within the hold and to seal the CO₂ lines and the hatch coaming drains. The bilge suctions must also be sealed to prevent ballast from leaking through the bilge system. Aboard some ships, the same coverplate is used for the bilge and the ballast suctions and must be unshipped from one position and bolted in place in the alternative position. Because of the time pressure which often exists when ballast holds have to be cleaned and ballasted, it is useful to consider the priorities

• Before a ballast hold is ballasted the ballast line must be unsealed and the bilge line, the CO₂ injection and the coaming drains must be sealed.

• Any sweepings or rubbish which could block the ballast suction must be removed from the hold.

• If the next cargo will or may require a high standard of cleanliness, the hold should be meticulously cleaned.

• If the ballast water is dirty, there may be an opportunity to deballast the hold and clean it during the voyage, if stress limitations permit, refilling with clean sea water thereafter if necessary.

• If there is no opportunity to clean the hold of ballast sediment at sea and a clean hold is required quickly in the loading port, the crew can usually commence hosing down the open hold from deck level whilst the ballast is still discharging and can enter the hold to continue washing down when the water level reaches 30-40 cm over the tanktop. It is important to remember that written permission to commence deballasting is required in many ports.

When the ballast has been discharged and washing down, if required, has been completed, a fresh water rinse will be required for cargoes which require holds which are free of salt. On completion of washing and rinsing the bilge suction, the CO₂ injection and the hatch coaming drains must be opened and tested and the ballast suction must be blanked off. Sufficient time to complete these tasks must be provided in the loading plan.