Pressure drop class

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The pressure loss class indicates the maximum pressure loss at the nominal flow rate  (Q3) of a water or heat meter .

In the case of water meters, the maximum pressure loss including all filters and sieves

  • Do not exceed 0.63 bar under rated conditions (Q3) 
  • with overload flow (Q4) do not exceed 1 bar.

Five pressure loss classes are defined, corresponding to the maximum permissible pressure loss in  kPa :

  • DP 63 (standard)
  • DP 40
  • DP 25
  • DP 16
  • DP 10.

The pressure loss class must be specified on water meters if it deviates from DP 63 (ΔP 63).


  • Pocket book on water supply (Johann Mutschmann / Fritz Stimmelmayr)