In a three-story apartment building protected with an NFPA 13R system utilizing quick-response sprinklers, the minimum density/area requirement is typically 0.10 gpm/ft². This density ensures adequate coverage for residential occupancies with a moderate level of combustibles.
References: NFPA 13R specifies requirements for the design and installation of sprinkler systems in residential occupancies up to four stories in height, including minimum density requirements.

For floor-stacked idle wood pallets, a design density of 0.225 gpm/ft² over a minimum design area is typically used for calculating water supply requirements. The larger area option (2,500 ft²) provides a more conservative approach to ensuring adequate protection.
References: Fire protection strategies for storage using NFPA 13 guidelines, considering the specific challenges posed by combustible commodities like wood pallets.

For supporting a 4 in. Schedule 10 sprinkler main with a trapeze hanger spanning 8 ft, a Schedule 40 pipe of at least 2 in. in diameter is typically recommended. This size provides adequate strength for the span and weight of the sprinkler main.
References: Engineering principles and best practices for hanger selection and sizing in sprinkler system installations.

The minimum distance a standard upright or pendant sprinkler can be installed from a wall is typically 4 inches (100 mm), ensuring adequate water distribution and preventing shadowed areas where the sprinkler's water spray may not reach.
References: NFPA 13 installation criteria for sprinklers, which specify placement relative to walls and other obstructions to ensure effective coverage.

When using standard upright sprinklers with beams framed into girders spaced on 7 ft centers, a maximum distance of 12 in. below the ceiling or roof deck is typically permitted. This ensures the sprinklers maintain effective coverage while accommodating architectural features.
References: NFPA 13 installation standards for upright sprinklers in relation to ceiling obstructions and beam configurations.