Where am I required to put cleanouts on a residential building drain and sewer, and how big?

IPC/IRC (Most US Jurisdictions):

Location Requirements (IPC 708 / IRC P3005):

1. Base of Stack: At the junction of the building drain and building sewer (inside or within 10 ft outside foundation).
2. Direction Changes: At every horizontal change of direction >45° (e.g., 90° elbows, tees). Not required on vertical stacks or 45° wyes.
3. Horizontal Distance: Maximum 100 ft intervals on horizontal runs.
4. Building Sewer: At the property line or connection to public sewer (often municipal requirement).
5. Accessibility: Must be accessible (IRC P3005.2). Do not bury under concrete without an access box. Cleanout plugs cannot be covered by permanent finish (tile, flooring).

Sizing (IPC Table 708.1 / IRC Table P3005.2): | Pipe Diameter | Min. Cleanout Size | | :--- | :--- | | 1½" – 2" | 1½" | | 2½" – 3" | 2½" | | 4" | 3½" (4" preferred) | | >4" | Same as pipe (up to 6") |

• Rule of Thumb: Cleanout size ≥ pipe size up to 4". For 4" pipe, a 4" cleanout (using a 4x4 wye + plug) is standard practice; 3½" is code minimum but harder to snake.
• Fittings: Use wye (Y) or combination wye-1/8 bend ("long sweep") for horizontal branches. Sanitary tees are prohibited for horizontal-to-horizontal connections (IPC 706.2).

UPC (CA, WA, OR, etc.):

• Similar locations, but max spacing is 50 ft on horizontal drains (UPC 707.4).
• Requires two-way cleanout at building sewer/drain junction (UPC 707.1).
• Sizing: Cleanout = Pipe size (no reduction allowed for 4").

Critical Pro Tip: Install a full-size 4" cleanout tee/wye at the foundation exit (two-way if UPC). This is your primary mainline access. Use brass or PVC plugs with square heads (not countersunk plastic) for future removal.

Verify local amendments. If excavating near utilities or public ROW, call 811.

Cleanouts are required on residential building drains and sewers per the International Plumbing Code (IPC), which is widely adopted in the U.S. (check local amendments, as some jurisdictions use UPC or have stricter rules).

Required Cleanout Locations (IPC 708):

1. At the junction of the building drain and building sewer – outside the foundation wall, within 3 ft of the building.
2. Every 100 feet along horizontal drainage piping (measured along the pipe’s developed length).
3. At each change of direction greater than 45° (i.e., long-sweep bends, not 90° elbows unless accessible via another cleanout).
4. At the base of each vertical stack (soil or waste stack) where it connects to the horizontal drain.
5. Where the building drain changes size (e.g., from 3" to 4").
6. At the upper terminal of each drain stack (via a cleanout or accessible fixture trap).

Minimum Cleanout Size (IPC 708.4):

• Same size as the pipe being cleaned, up to 4".
• For pipes larger than 4", a 4" cleanout is the minimum required size.
• Cleanouts must be accessible and not concealed behind permanent finishes without access panels.

Practical Notes:

• Use two-way cleanouts at the building drain/sewer junction for flexibility.
• Avoid placing cleanouts under concrete slabs without access sleeves or vaults.
• For PVC/ABS, use cleanout tees or sanitary tees with threaded plugs (not reducing couplings).
• Always verify with your local AHJ (Authority Having Jurisdiction)—some areas require cleanouts every 50 ft or have additional rules for septic vs. municipal sewer.

> ⚠️ Note: If work involves the main sewer line beyond the property line or requires breaking into a public sewer, a licensed plumber or contractor may be required by law. DIY is allowed for interior drain work in most areas, but exterior sewer connections often need permits and inspection.

Keep it accessible, sized right, and spaced per code—this prevents costly future blockages.