14.2 Using the Provided Tables Fast (702.1, 610.3, 610.4, 610.10) and Writing the Missing Ones from Memory

Table 702.1: Drainage Fixture Unit Values

Layout: fixture name, then minimum size trap and trap arm, then DFU columns for private, public, and assembly. Sinks are grouped under a "Sinks" heading. Water closets are split by flush volume (1.6 gpf, or more) and type.

Lookup habits:

1. Decide the occupancy column before looking up any fixture, and stay in it.
2. Scan for the right variant. Urinals come in integral-trap 1.0 gpf, integral-trap over 1.0 gpf, and exposed-trap versions. Service sinks come with 2-inch and 3-inch traps and a flushing-rim version.
3. Dashes mean the fixture is not rated for that occupancy.
4. Read the notes. Note 2 gives a 2-inch minimum drain for kitchen and laundry sinks, dishwashers, some sinks, and urinals. Note 5: a battery of three or more clothes washers counts 6 DFU each for common piping. Note 1: indirect waste receptors are sized from Table 702.2(2).

Table 610.3: Water Supply Fixture Units

Layout: fixture, then minimum fixture branch pipe size, then WSFU for private, public, and assembly.

Lookup habits:

1. Flushometer water closets and urinals say "See Footnote 7", meaning Table 610.10. Do not look for a number in 610.3.
2. Note 3: listed values are the load on the cold building supply. For separate hot and cold branches, take 3/4 of the listed value on each side.
3. Note 8: the second and later hose bibbs are 1.0 on shared piping, but each hose bibb branch is sized at 2.5.
4. Note 5: continuous flows are added separately in gpm.
5. Minimum branch sizes are floors: 1 inch for flushometer water closets, 3/4 inch for flushometer urinals and 3/4-inch tub fillers, and 1/2 inch for most others.

Table 610.4: Water Pipe and Meter Sizes

Layout: three stacked groups, 30–45 psi, 46–60 psi, and over 60 psi. Each group has rows for combinations of meter and street service size and building supply and branch size. The length columns run 40 through 1,000 feet. The cells hold the maximum fixture units.

Lookup sequence (610.8):

1. Adjusted pressure: minimum pressure, minus device losses, minus 1/2 psi per foot to the highest outlet (or 80% of a regulator's setting).
2. Pick the group (pressure range).
3. Pick the length column equal to or longer than the developed length.
4. Read down that column to the first value at least equal to the load. Use a ruler edge or your pencil to keep your place, because the rows are dense.
5. Read the meter and supply sizes from the left of that row.

Traps: The rows are ordered by combination, so values do not rise steadily down the column. For example, the 1-inch meter with 2-inch supply row holds 85 in many columns, below the rows above it. Read in order and stop at the first adequate value. Building supply is never under 3/4 inch (note 2).

Table 610.10: Flushometer Fixture Units

Habit: For each pipe section, count the valves downstream of it (the valves that section serves), look up the cumulative value, and add the other fixtures at their Table 610.3 values.

Tables You Must Carry in Your Head

At the start of each drawing portion, write this template on your scratch paper:

Table 703.2 (drainage):

Table 703.2 (vents): 1-1/4 = 1 DFU / 45 ft; 1-1/2 = 8 / 60; 2 = 24 / 120; 3 = 84 / 212; 4 = 256 / 300. Individual vent: at least 1-1/4 inches and at least half the drain; no more than one-third horizontal.

Table 1002.2 (trap arm to vent): 1-1/4 = 30 in; 1-1/2 = 42 in; 2 = 60 in; 3 = 72 in; 4 = 120 in; water closet 6 ft from the flange.

Areas: 1-1/4 = 1.23; 1-1/2 = 1.77; 2 = 3.14; 3 = 7.07; 4 = 12.57 square inches.

For Part 1, add: Table 313.3 hanger spacing (Section 1.4), Table 603.3.1 air gaps (Section 5.3), Table 707.1 cleanouts and Washington's 707.9 clearances (Section 7.1), and Washington's Table 501.1 first hour ratings (Section 3.1).

Practice Drill

Time yourself for each:

1. From memory, write Table 703.2's drainage and vent rows. The target is under 2 minutes.
2. On a printed Table 702.1, look up 10 mixed fixtures in the public column. The target is under 90 seconds.
3. On Table 610.4, answer: 46–60 psi, 150 ft, 97 FU. The answer is a 1-1/2-inch meter and 1-1/2-inch supply (128). Then: over 60 psi, 200 ft, 60 FU. Reading down that column (4, 13, 30, 32, 39, 62), the first adequate row is the 1-inch meter with 1-1/4-inch supply (62).
4. Table 610.10: what do 6 flushometer water closets carry? The answer is 115 + 10 = 125.