Drainage Cleanout Layout (IPC 708)
Two code triggers put cleanouts in a drain and they ADD, so counting from either alone comes out low.
Example
You enter
- Horizontal drain run (ft) 240
- Maximum cleanout spacing (ft; IPC 100) 100
- Changes of horizontal direction over 45 degrees 9
- Waste or soil stacks 2
- Cleanout / pipe size (in) 4
- Clear space at the opening (in) 18
- Crawl-space pathway height (in; 0 = not in a crawl space) 30
You get
- From spacing 2
- Change cap 6
- From changes of direction 6
- Stack bases (practice, not in the code total) 2
- Total cleanouts 8
Checked against published worked examples from: International Code Council.
Details, formula, and sources
ScopeSpacing not more than 100 ft along the horizontal run, and a cleanout at every change of horizontal direction over 45 degrees. A cleanout at the base of each stack is good practice but no longer an IPC 2021 section 708 requirement, so it is reported on top of the code count. The allowance that keeps a bendy run sane is the grouping rule -- where more than one such change happens within 40 ft of developed length, the cleanout at the FIRST serves them all, which caps the change-driven count at ceil(run/40) however many bends are drawn. A 240 ft run with nine bends needs 8 by the code (2 for spacing, 6 for changes), not 11, because the cap governs at six; two stack-base cleanouts would come on top. Also checks access, which is where cleanouts get value-engineered into uselessness: 18 in of clear space at the opening for 6 in and smaller, and 24 in of unobstructed pathway height in a crawl space -- one you cannot reach and turn does not count.
Formula or tablespacing cleanouts = max(0, ceil(run / max spacing) - 1), assuming the run begins at one; change cleanouts = min(changes - grouped away, ceil(run / 40)); stack cleanouts = one per waste or soil stack, reported as practice only; total = spacing + change cleanouts (stacks are left out). Access passes when a cleanout 6 in and smaller has at least 18 in of clear space at the opening and, in a crawl space, at least 24 in of unobstructed pathway height.
Source and editionIPC 708 - horizontal drains provided with cleanouts not more than 100 ft apart; a cleanout at each change of horizontal direction greater than 45 degrees, with the cleanout at the first change serving all changes occurring within 40 ft of developed length; not less than 18 in of clear space at the opening of cleanouts 6 in and smaller; and not less than 24 in of unobstructed pathway height where a cleanout is located in a crawl space.
Free accessAll four provisions are short prescriptive sentences reproduced in state and municipal adoptions and trade commentary. No table is reproduced and the spacing limit is an editable input.
What governsEstimate. AHJ and licensed professional govern.
API field nameshorizontal_run_ft, max_spacing_ft, direction_changes, stack_count, pipe_size_in, clear_space_in, crawl_height_in, spacing_cleanouts, change_cap, change_cleanouts, stack_cleanouts, total_cleanouts
- Spacing not more than 100 ft apart on horizontal drains; editableIPC 708.1.1
- Changes of direction one per change greater than 45 degreesIPC 708.1.4
- Grouping allowance the first change serves all within 40 ft, capping the count at ceil(run/40)IPC 708
- Stack bases reported as practice only; IPC 2021 and 2027 708.1.1-708.1.12 have no base-of-stack cleanout rule, so it is not in the code totalIPC 2027 708 (absence; also 2021)
- Access 18 in clear at the opening for 6 in and smaller; 24 in pathway height in a crawl spaceIPC 708
- Run starts at a cleanout stated assumption; add one at the head if it does notstated assumption