When both internal and external surfaces are to be galvanized at least one filling and draining hole must be provided, with a vent diagonally opposite to allow the exit of air during immersion. Check the drainage table for minimum drainage and vent hole sizes for various tank capacities.
Internal baffles should be cropped. Manholes should finish flush inside to prevent trapping excess zinc.
When vessels and air receivers etc. are not to be galvanized inside, ‘snorkel’ tubes or extended vent pipes may be fitted only after discussion with your local Perry Metal Protection representative to allow air to exit above the level of molten zinc in the galvanizing bath.