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ANNEX IIIU.K. Measurements and calculations
For the purposes of compliance and verification of compliance with the requirements of this Regulation, measurements and calculations shall be made using harmonised standards the reference numbers of which have been published in the Official Journal of European Union, or using other reliable, accurate and reproducible methods, which take into account the generally recognised state of the art, and produce results deemed to be of low uncertainty. They shall fulfil all of the following technical parameters.
The hydraulic pump efficiency, as defined in Annex I, is measured at the head and flow corresponding to the best efficiency point (BEP), part load (PL) and over load (OL) for full impeller diameter with clean cold water.
The formula for calculating the required minimum efficiency at best efficiency point (BEP) is as follows: 
Where,
x = ln (ns); y = ln (Q) and ln = natural logarithm and Q = flow in [m3/h]; ns = specific speed in [min–1]; C = value found in Table.
The value of C depends on the pump type and nominal speed, and also the MEI value.
Table
Minimum efficiency index (MEI) and its corresponding C-value depending on the pump type and speed
| C-value for MEICPumpType,rpm | MEI = 0,10 | MEI = 0,40 |
|---|---|---|
| C (ESOB, 1 450) | 132,58 | 128,07 |
| C (ESOB, 2 900) | 135,6 | 130,27 |
| C (ESCC, 1 450) | 132,74 | 128,46 |
| C (ESCC, 2 900) | 135,93 | 130,77 |
| C (ESCCi, 1 450) | 136,67 | 132,3 |
| C (ESCCi, 2 900) | 139,45 | 133,69 |
| C (MS-V, 2 900) | 138,19 | 133,95 |
| C (MSS, 2 900) | 134,31 | 128,79 |
The requirements for part load (PL) and over load (OL) conditions are set at slightly lower values than those for 100 % flow (ηΒΕΡ).
All efficiencies are based on full (untrimmed) impeller. Vertical multistage water pumps are to be tested with a 3 stage (i = 3) version. Submersible multistage water pumps are to be tested with a 9 stage (i = 9) version. If this number of stages is not offered within the specific product range the next higher number of stages within the product range is to be chosen for testing.