## UPC 2018

#### Appendix M Peak Water Demand Calculator

Heads up: There are no amended sections in this chapter.

# Appendix M Peak Water Demand Calculator

### M 101.1 Applicability

This appendix provides a method for estimating the demand load for the building water supply and principal branches for single- and multi-family dwellings with water-conserving plumbing fixtures, fixture fittings, and appliances.

### M 102.1 Water-Conserving Fixtures

Plumbing fixtures, fixture fittings, and appliances shall not exceed the design flow rate in Table M 102.1.
TABLE M 102.1
DESIGN FLOW RATE FOR WATER-CONSERVING PLUMBING
FIXTURES AND APPLIANCES IN RESIDENTIAL OCCUPANCIES
FIXTURE AND APPLIANCE MAXIMUM DESIGN FLOW RATE
(gallons per minute)
Bar Sink 1.5
Bathtub 5.5
Bidet 2.0
Clothes Washer* 3.5
Combination Bath/Shower 5.5
Dishwasher* 1.3
Kitchen Faucet 2.2
Laundry Faucet (with aerator) 2.0
Lavatory Faucet 1.5
Water Closet, 1.28 GPF Gravity Tank 3.0

For SI units: 1 gallon per minute = 0.06 L/s

* Clothes washers and dishwashers shall have an energy star label.

### M 102.2 Water Demand Calculator

The estimated design flow rate for the building supply and principal branches and risers shall be determined by the IAPMO Water Demand Calculator available for download at http://www.iapmo.org/WEStand/Pages/WaterDemandCalculator.aspx

### M 102.3 Meter and Building Supply

To determine the design flow rate for the water meter and building supply, enter the total number of indoor plumbing fixtures and appliances for the building in Column [B] of the Water Demand Calculator and run Calculator. See Table M 102.3 for an example.

TABLE M 102.3
WATER DEMAND CALCULATOR EXAMPLE

[A]
FIXTURE
[B]
ENTER NUMBER OF FIXTURES
[C]
PROBABILITY OF USE (%)
[D]
ENTER FIXTURE FLOW RATE (GPM)
[E]
MAXIMUM RECOMMENDED FIXTURE FLOW RATE (GPM)
1 Bar Sink 0 2.0 1.5 1.5
2 Bathtub 0 1.0 5.5 5.5
3 Bidet 0 1.0 2.0 2.0
4 Clothes Washer 1 5.5 3.5 3.5
5 Combination Bath/Shower 1 5.5 5.5 5.5
6 Dishwasher 1 0.5 1.3 1.3
7 Kitchen Faucet 1 2.0 2.2 2.2
8 Laundry Faucet 0 2.0 2.0 2.0
9 Lavatory Faucet 1 2.0 1.5 1.5
10 Shower, per head 0 4.5 2.0 2.0
11 Water Closet, 1.28 GPF Gravity Tank 1 1.0 3.0 3.0
12 Other Fixture 1 0 0.0 0.0 6.0
13 Other Fixture 2 0 0.0 0.0 6.0
14 Other Fixture 3 0 0.0 0.0 6.0
Total Number of Fixtures 6 RESET RUN WATER DEMAND CALCULATOR
99th Percentile Demand Flow = 8.5 GPM

### M 102.4 Fixture Branches and Fixture Supplies

To determine the design flow rate for fixture branches and risers, enter the total number of plumbing fixtures and appliances for the fixture branch or riser in Column [B] of the Water Demand Calculator and run Calculator. The flow rate for one fixture branch and one fixture supply shall be the design flow rate of the fixture according to Table M 102.1.

### M 102.5 Continuous Supply Demand

Continuous supply demands in gallons per minute (gpm) for lawn sprinklers, air conditioners, hose bibbs, etc., shall be added to the total estimated demand for the building supply as determined by Section M 102.3. Where there is more than one hose bibb installed on the plumbing system, the demand for only one hose bibb shall be added to the total estimated demand for the building supply. Where a hose bibb is installed on a fixture branch, the demand of the hose bibb shall be added to the design flow rate for the fixture branch as determined by Section M 102.4.

### M 102.6 Other Fixtures

Fixtures not included in Table M 102.1 shall be added in Rows 12 through 14 in the Water Demand Calculator as Other Fixture. The probability of use and flow rate for Other Fixtures shall be added by selecting the comparable probability of use and flow rate from Columns [C] and [E],

### M 102.7 Size of Water Piping Per Appendix A

Except as provided in Section M 102.0 for estimating the demand load for single- and multi-family dwellings, the size of each water piping system shall be determined in accordance with the procedure set forth in Appendix A. After determining the permissible friction loss per 100 feet (30 480 mm) of pipe in accordance with Section A 104.0 and the demand flow in accordance with the Water Demand Calculator, the diameter of the building supply pipe, branches and risers shall be obtained from Chart A 105.1(1) through Chart A 105.1(7), whichever is applicable, in accordance with Section A 105.0 and Section A 106.0. Velocities shall be in accordance with Section A 107.0. Appendix I, Figure 3 and Figure 4 shall be permitted when sizing PEX systems.

M102.7.1 Minimum Fixture Branch Size. The minimum fixture branch size shall be 1/2 inch (15 mm) in diameter.

### M 102.8 Examples Illustrating Use of Water Demand Calculator With Appendix A

Example 1: Indoor Water Use Only — Use the information given below to find the pipe size for the building supply to a residential building with six indoor fixtures as shown in Figure 1 [Pipe Section 4].

Given Information:

 Type of construction: Residential, one-bathroom Friction loss per 100 ft: 15 psi Type of pipe material: L-copper Maximum velocity: 10 ft/s Fixture number/type: 1 combination bath/shower 1 kitchen faucet 1 lavatory faucet 1 dishwasher 1 WC 1 clothes washer

FIGURE 1
RESIDENTIAL BUILDING WITH SIX INDOOR FIXTURES

Solution: Step 1 of 2 — Find Demand Load for the Building Supply.

The Water Demand Calculator [WDC] in Figure 2 is used to determine the demand load expected from indoor water use. The WDC has white-shaded cells and light gray-shaded cells. The values in the light gray cells are derived from a national survey of indoor water use at homes with efficient fixtures and cannot be changed.

The white-shaded cells accept input from the designer. For instance, fixture counts from the given information are entered in Column [B]; the corresponding recommended fixture flow rates are already provided in Column [D]. The flow rates in Column [D] may be reduced only if the manufacturer specifies a lower flow rate for the fixture. Column [E] establishes the upper limits for the flow rates entered into Column [D]. Clicking the Run Water Demand Calculator button gives 8.5 gpm as the estimated indoor water demand for the whole building. This result appears in the dark gray box of the WDC in Figure 2.

[A]
FIXTURE
[B]
ENTER NUMBER OF FIXTURES
[C]
PROBABILITY OF USE (%)
[D]
ENTER FIXTURE FLOW RATE (GPM)
[E]
MAXIMUM RECOMMENDED FIXTURE FLOW RATE (GPM)
1 Bar Sink 0 2.0 1.5 1.5
2 Bathtub 0 1.0 5.5 5.5
3 Bidet 0 1.0 2.0 2.0
4 Clothes Washer 1 5.5 3.5 3.5
5 Combination Bath/Shower 1 5.5 5.5 5.5
6 Dishwasher 1 0.5 1.3 1.3
7 Kitchen Faucet 1 2.0 2.2 2.2
8 Laundry Faucet 0 2.0 2.0 2.0
9 Lavatory Faucet 1 2.0 1.5 1.5
10 Shower, per head 0 4.5 2.0 2.0
11 Water Closet, 1.28 GPF Gravity Tank 1 1.0 3.0 3.0
12 Other Fixture 1 0 0.0 0.0 6.0
13 Other Fixture 2 0 0.0 0.0 6.0
14 Other Fixture 3 0 0.0 0.0 6.0

Total Number of Fixtures 6   RESET RUN WATER DEMAND CALCULATOR
99th Percentile Demand Flow = 8.5 GPM

FIGURE 2
WATER DEMAND CALCULATOR FOR INDOOR USE AT HOME WITH SIX EFFICIENT FIXTURES (EXAMPLE 1).

Solution: Step 2 of 2 — Determine the Pipe Size of the Building Supply.

Chart A 105.1(1) for copper piping systems (from Appendix A of the UPC, shown in Figure 3) is used to determine the pipe size, based on given friction loss, given maximum allowable pipe velocity, given pipe material and the demand load computed in Step 1. In Figure 3, the intersection of the given friction loss (15 psi) and the maximum allowable pipe velocity (10 ft/s) is labeled point A. The vertical line that descends from point A to the base of the chart intersects four nominal sizes for L-copper pipe. These intersection points are labeled B, C, D, E and correspond to pipe sizes of 1 inch (25 mm), 3/4 inch (20 mm), 1/2 inch (15 mm) and 3/8 inch (10 mm), respectively. A horizontal line from points B, C, D, E to the right-hand side of the chart gives maximum flow rates of 24 gpm, 12 gpm, 4.5 gpm, and 2.3 gpm, respectively. These results are summarized in Table 1 which shows that a 3/4 inch (20 mm) type L copper line is the minimum size that can convey the peak water demand of 8.5 gpm.

TABLE 1
PIPE SIZE OPTIONS FOR BUILDING SUPPLY
POINT IN FIGURE 3 PIPE DIAMETER (INCH) MAXIMUM FLOW (GPM) OK FOR BUILDING SUPPLY*
E 3/8 2.3 No
D 1/2 4.5 No
C 3/4 12 Yes
B 1 24 Yes

For SI units: 1 inch = 25 mm, 1 gallon per minute = 0.06 L/s

* For Building in Examples 1, 2, 3, and 4.

FIGURE 3
CHART A 105.1(1) FOR FINDING PIPE SIZE

Example 2: Indoor and Outdoor Water Use — Find the pipe size for the building supply [Figure 1, Pipe Section 4] if the building in Example 1 adds two outdoor fixtures (hose bibb, each with a fixture flow of 2.0 gpm).

Solution: Step 1 of 2 — Find Demand Load for the Building Supply.

The WDC has been developed exclusively for peak indoor water use which can be viewed as a high-frequency short duration process. Because fixtures for outdoor water use may operate continuously for very long periods, they are not included in the WDC. To account for water use from one or more outdoor fixtures, add the demand of the single outdoor fixture with the highest flowrate to the calculated demand for indoor water use. With two hose bibbs, the demand of only one hose bibb is included. Hence, in this example, the total demand for the whole house is 8.5 gpm + 2.0 gpm = 10.5 gpm.

Solution: Step 2 of 2 — Determine the Pipe Size of the Building Supply.

Table 1 shows that at 10.5 gpm the building supply shall be 3/4 inch (20 mm) in diameter.

Example 3: Indoor, Outdoor and Other Fixture Water Use — Find the pipe size for the water supply [Figure 1, Pipe Section 4] if the building in Example 2 adds a kitchen pot filler and a dog bath each with a faucet flow rate of 5.5 gpm.

Solution: Step 1 of 2 — Find Demand Load for the Building Supply.

The kitchen pot filler and dog bath are not listed in Column [A] of the WDC. To accommodate cases such as this, the WDC provides up to three additional rows for "Other Fixtures". Enter the kitchen pot filler and dog bath in Column [A] of the WDC and enter the fixture count for each in Column [B]. Find an indoor fixture that has a similar probability of use in Column [C] and add that to the column. Finally, enter the flow rate of the kitchen pot filler and dog bath in Column [D]. The estimated indoor water demand for the whole building is 11 gpm, as shown in the WDC in Figure 4. As illustrated in Example 2, the hose bibb will increase the total demand for the whole house to 13 gpm.

Note that a reset button is provided to clear any numbers in Column [B] from a previous calculation.

Solution: Step 2 of 2 — Determine the Pipe Size of the Building Supply.

Table 1 shows that at 13 gpm the building supply shall be 1inch (25 mm) in diameter.

Example 4: Sizing Branches and Risers — For individual hot and cold branches, repeat Steps 1 and 2. For example, for the hot water branch at the water heater [Figure 1, Pipe Section 3], enter all the fixtures and appliances that use hot water into the Water Demand Calculator (toilets will be excluded) as seen in Figure 5. Use the calculated demand load to find the pipe size in Step 2. Table 1 shows that at 7.7 gpm, the hot water branch shall be 3/4 inch (20 mm) in diameter.

For each additional hot and cold branch [Figure 1, Pipe Sections 1 and 2], enter the number of fixtures and appliances served by that branch into the WDC and use that demand in Step 2 to determine the branch size. If the branch serves a hose bibb, add the demand of the hose bibb to the calculated demand flow for the branch. As discussed in Example 2, the hose bibb is not to be entered into WDC, since the Calculator is for indoor uses only.

When there is only one fixture or appliance served by a fixture branch, the demand flow shall not exceed the fixture flow rate in Column [E] of the Water Demand Calculator. The fixture flow rate would be used in Step 2 to determine the size of the fixture branch and supply.

[A]
FIXTURE
[B]
ENTER NUMBER OF FIXTURES
[C]
PROBABILITY OF USE (%)
[D]
ENTER FIXTURE FLOW RATE (GPM)
[E]
MAXIMUM RECOMMENDED FIXTURE FLOW RATE (GPM)
1 Bar Sink 0 2.0 1.5 1.5
2 Bathtub 0 1.0 5.5 5.5
3 Bidet 0 1.0 2.0 2.0
4 Clothes Washer 1 5.5 3.5 3.5
5 Combination Bath/Shower 1 5.5 5.5 5.5
6 Dishwasher 1 0.5 1.3 1.3
7 Kitchen Faucet 1 2.0 2.2 2.2
8 Laundry Faucet 0 2.0 2.0 2.0
9 Lavatory Faucet 1 2.0 1.5 1.5
10 Shower, per head 0 4.5 2.0 2.0
11 Water Closet, 1.28 GPF Gravity Tank 1 1.0 3.0 3.0
12 Pot Filler 1 2.0 5.5 6.0
13 Dog Bath 1 1.0 5.5 6.0
14 Other Fixture 3 0 0.0 0.0 6.0

Total Number of Fixtures 8   RESET RUN WATER DEMAND CALCULATOR
99th Percentile Demand Flow = 11.0 GPM

FIGURE 4
WATER DEMAND CALCULATOR TO ACCOMMODATE OTHER FIXTURES (EXAMPLE 3).

[A]
FIXTURE
[B]
ENTER NUMBER OF FIXTURES
[C]
PROBABILITY OF USE (%)
[D]
ENTER FIXTURE FLOW RATE (GPM)
[E]
MAXIMUM RECOMMENDED FIXTURE FLOW RATE (GPM)
1 Bar Sink 0 2.0 1.5 1.5
2 Bathtub 0 1.0 5.5 5.5
3 Bidet 0 1.0 2.0 2.0
4 Clothes Washer 1 5.5 3.5 3.5
5 Combination Bath/Shower 1 5.5 5.5 5.5
6 Dishwasher 1 0.5 1.3 1.3
7 Kitchen Faucet 1 2.0 2.2 2.2
8 Laundry Faucet 0 2.0 2.0 2.0
9 Lavatory Faucet 1 2.0 1.5 1.5
10 Shower, per head 0 4.5 2.0 2.0
11 Water Closet, 1.28 GPF Gravity Tank 0 1.0 3.0 3.0
12 Other Fixture 1 0 0.0 0.0 6.0
13 Other Fixture 2 0 0.0 0.0 6.0
14 Other Fixture 3 0 0.0 0.0 6.0

Total Number of Fixtures 5   RESET RUN WATER DEMAND CALCULATOR
99th Percentile Demand Flow = 7.7 GPM

FIGURE 5
WATER DEMAND CALCULATOR FOR THE HOT WATER BRANCH (EXAMPLE 4).