Parts Fittings/Bulk Heads. Lifegard Aquatics Bulkhead. Always make sure that you have drilled the appropriate size hole to accommodate your bulk head. The rubber bushing always goes on the 'wet' side of the tank or resevoir for a water tight seal. Parts Fittings/Bulk Heads. Lifegard Aquatics Bulkhead Threaded 2" Bulkheads require a 3" Hole Size. 2" FPT on the top and bottom of the bulkhead.