Choosing the proper pipe size

The following pipe sizes are the minimum required pipe size for single fixtures and are subject varying code regulations. When other fixtures are added to the same pipe, the size may increase.

Drainage sizes

Fixture Size in Inches Size in Millimeters
Bathtub 1 ½ 40
Beer cabinet 1 ½ 40
Bidet 1 ¼ 32
Dishwasher 1 ½ 40
Floor drain 2 50
Laundry tub 1 ½ 40
Lavatory - single or double (bathroom sink) 1 ¼ 32
Shower 1 head 1 ½ 40
shower 2-3 heads 2 50
Kitchen Sink - single or double 1 ½ 40
Toilet / water closet 3 80

Water supply pipe sizes

Fixture Size in Inches Size in Millimeters
Bathtub ½ 15
clothes washer ½ 15
Dishwasher ½ 15
Hose bibb ½ 15
Lavatory ⅜ 10
Kitchen sink ½ 15
Shower head ½ 15
Water closet (tank type) ⅜ 10