Bathroom Group vs Individual Fixture Counting

What a Bathroom Group Is

IPC Section 202: a water closet, a lavatory, and a bathtub or shower, including or excluding a bidet, located together on the same floor level. That is a full bath. A powder room is not a group. A basement WC by itself is not a group. Two baths on two floors are two groups, not one.

Table E103.3(2) private flush-tank bathroom group: 2.7 cold / 1.5 hot / 3.6 total WSFU. Flushometer-valve group: 8.0 total (rare in a house). Table 709.1: 5 DFU if the water closet is 1.6 gpf or less, 6 DFU if it flushes more. Note f: fixtures added to the group (a second lav, a bidet you did not already exclude) add their own DFU on top of 5 or 6.

What Individual Counting Is

Private flush-tank WC 2.2 WSFU / 3 DFU. Private lav 0.7 / 1. Private tub 1.4 / 2. Private shower 1.4 / 2. A tub with a showerhead over it is still 2 DFU (709.1 note b) and still 1.4 WSFU for the tub row — you do not add the shower row on the same fixture.

WC + lav + tub as pieces: 4.3 WSFU and 6 DFU. The group is 3.6 and 5. The pieces are higher because they do not get the in-room diversity the group table already baked in. For one bathroom either method is used in the field; for a whole house, mixing them (group for bath 1, pieces for bath 1) is how totals inflate.

When to use which

Use the group when the room matches Section 202 and you want the table’s in-room diversity. Use pieces when the room is incomplete, when fixtures are split across rooms, or when you are sizing a single fixture branch (the lav branch does not inherit the group number). Never use both on the same fixtures. The calculator flags that mix.