Demand type of water taps

Product	InstalSystem 5
Type of article	TIP&TRICK
Source for translation	2026-03-04

Problem description

During the Designing of water supply system installation, the program offers three options to determin the Demand type for water supply taps, available for selection in the Data table window:

• Normative,
• Continuous,
• Not considered.
  

  

  1. Demand type.

  
  

These options have a direct impact on the performance of Water supply systems calculations.

Solution

Normative

The method is intended for сalculations of outflows in pipe-runs feeding taps with variable demand:

1. In the pipe-runs connected directly or indirectly (e.g. a series of connected pipe-runs) to a single Receptor with variable demand (regardless of their location):
   • V_variable = V_R, [dm³/s], where:
     • V_R - Normative outflow of Receptor;
2. In other pipe-runs feeding several Receptors with only variable demand - based on a general formula common to all the standards:
   • V_variable = a * (ΣV_R) ^ b + c, [dm³/s], where:
     • a, b, c - coefficients taking different numerical values, depending on the type of building for a given Calculation standard,
     • ΣV_R - Sum of normative outflows of Receptors.
       

Note! The calculated values of the components of the above formulas, such as coefficients (a, b, c), Normative outflow (V_R) and the scope of application of the formulas depending on Sum of normative outflows (ΣV_R), are imposed by a Calculation standard, selected in the General data window. For more information, see: Defining catalogues and general data.

Continuous

The method is intended for сalculation of flows in pipe-runs feeding taps with Continuous demand:

• Vc = ΣVc, [dm³/s], where:
  • Vc - Continuous outflow of Receptor.

Note! Hydrant outflows ARE NOT taken into account in the calculation of Continuous demand, but ARE taken for the calculation of simultaneous flow. Number of hydrants for the particular pipe-run is determined in accordance with the data set in the General data window:

2. Calculation standards and options.

Not considered

If the option Not considered is set, it means that this Receptor is not taken into account in the calculations. In this case, the outflow in the pipe-runs is calculated as follows:

1. For the pipe-runs feed directly the Receptor and in series with several Receptors:
   • V_S=V_R, [dm³/s], where:
     • V_S - Volumetric flow rate in the pipe-run,
     • V_R - Normative outflow of Receptor;
2. If ONLY Receptors that are Not considered are located at the end of the branch of the installation (coming from the Source), then the outflow in the pipe-run collecting the pipes connected to these appliances is determined as the maximum (V of pipe-runs from the Receptor);
   
3. If a pipe-run feeding Not considered Receptors is connected to a pipe-run feeds (directly or indirectly through other pipe-runs) Receptors with Normative (variable) / Continuous demand / Hydrant, the outflow in such a pipe-run is calculated as the simultaneous and DOES NOT TAKE INTO ACCOUNT the Normative demands from Not considered Receptors;
4. For the pipe-runs connected indirectly in addition to Not considered Receptors, at least to two Receptors with Normative (variable) demand, the outflow is determined in accordance with the relevant standard method for Normative outflow.

Note! Not considered Receptors are included in the hydraulic Calculations in the same way as other Receptors:

1. The program determines pressure losses in pipe-runs connected (directly or indirectly) to the Not considered Receptors based on the outflow values in these pipe-runs (and displays them as hints and in the Results tables);
2. Not considered Receptor can become a critical receiver (occur Critical hydraulic route – a route with the greatest pressure losses).

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