Selection of Water Supply Installation Diameters
31 października 2022 | Water Supply
The selection of water supply installation diameters is not complicated. It involves checking how many and what type of fixtures will be served by a given pipe section. Based on this, the flow is calculated and then the diameters are selected based on velocity criteria.
Sanitary Fixtures
The PN-92/B-01706 standard "Water Supply Installations -- Design Requirements" presents normative outflows from draw-off points. For each section, the sum of normative outflows, so-called Σqn, must be calculated. From this value, the design flow is then determined.
For example, the last section of the riser supplying water to the apartment on the highest floor serves the following fixtures:
- flush tank 0.13
- washbasin 0.07
- kitchen sink 0.07
- washing machine 0.25
- shower 0.15
The sum qn for this apartment will be Σqn = 0.67 dm3/s
Table 1 - Normative Outflows
Design Flow
Having established the sum qn, we can immediately proceed to determine the design flow. According to the PN-92/B-01706 standard, we have a series of formulas depending on the type of buildings and the sum qn. For the above calculation Σqn = 0.67 dm3/s for residential building purposes, the design flow is 0.43 dm3/s.
Table 2 - Design Flows
Selection of Water Supply Installation Diameters
For the purpose of selecting the diameter of a given section, the flow velocity must be determined based on the previously calculated flow. A properly selected pipe diameter ensures a flow not greater than shown in the table below. For the above calculations, the calculator selected Pex 25x2.5 pipe diameters based on the velocity criterion < 1.5 m/s
Pipe Type | PN-92/B-01706 [m/s] | DIN 1988 [m/s] |
|---|---|---|
Connections from riser to draw-off points | 1.5 | 2.0 |
Risers in water supply installations | 1.5 | 2.0 |
Distribution pipes | 1.0 | 1.5 |
Water supply connections | 1.0 | 1.5 |
Table 3 - Velocity Criteria
Automatic Calculations
For calculating extensive installations, calculators that automatically select pipe diameters depending on the number of sanitary fixtures are helpful. The application available at this link allows for selecting water supply pipe diameters. It is sufficient to enter the number of fixtures supplied by a given section. Additionally, it is possible to copy calculations and add more fixtures.
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