For all residential properties
Updated: 04/13/2026

Condensate from air-conditioning systems and water heaters must terminate as outlined below. Always check the current Building, Plumbing, and Mechanical codes to verify requirements and additionally consult any manufacturer installation instructions.

TERMINATION OPTIONS

Condensates may terminate via an air gap or air break to any of the following:

  • A trapped, vented receptacle, e.g., a standpipe receptor, mop sink, or floor sink 
  • A dry well — see options below
  • The tail piece of plumbing fixtures
  • A bioswale (landscape retention area) designed to handle the additional condensate load
  • Additional options:
  • On single-family/duplex properties - Heat pump water heaters may terminate at any exterior surface that is not part of a main entrance to residence or paths of egress. Provide splash block at landscape terminations.

  • On commercial properties - Condensate from commercial equipment may terminate at a roof drain only if that drain is directly connected to a storm drainage system and does not daylight to the site.

  • For equipment/appliances located in an attic, furred space, or dropped ceiling - Please refer to Mechanical and Plumbing codes for secondary protection requirements. CMC 310.2 and CPC 814.2

Drywell Option 1
NOT FOR COOLING EQUIPMENT EXCEEDING 200 TONS

  • Minimum size: 2' square X 2' deep
  • Location: Minimum 3' from structure/foundation to nearest drywell edge
  • Cover: Cover top of drywell with building paper or plastic sheeting, then add 6" of earth or concrete.
  • Connection: Minimum ¾" condensate pipe must indirectly connect to a minimum 1-1/2" drainpipe. The indirect connection must be made by an air gap or air break at the edge of foundation.
  • Fill: Fill with 1" rock or gravel.

Schematic of a below-ground drywell - Residential Properties

Drywell Option 2

  • Drywell rings: Use 24" diameter grade rings. Minimum two rings for up to 30 tons of cooling; for each additional 30 tons, add two rings.
  • Location: Minimum 8' from structure/foundation to nearest drywell edge
  • Cover: Provide a solid concrete cover.
  • Connection: A minimum ¾" condensate pipe must indirectly connect to a minimum 1-1/2" drainpipe. The indirect connection must be made by an air gap or air break at the edge of foundation.
  • Fill: Surround bottom and sides with minimum 6" layer of 1" rock or gravel.

Schematic of a drywell - Non-Residential Properties

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