  The electron capture in $^{163}\mathrm{Ho}$ experiment (ECHo) is designed to
directly measure the effective electron neutrino mass by analysing the endpoint
region of the $^{163}\mathrm{Ho}$ electron capture spectrum. We present a data
reduction scheme for the analysis of high statistics data acquired with the
first phase of the ECHo experiment, ECHo-1k, to reliably infer the energy of
$^{163}\mathrm{Ho}$ events and discard triggered noise or pile-up events. On a
first level, the raw data is filtered purely based on the trigger time
information of the acquired signals. On a second level, the time profile of
each triggered event is analysed to identify the signals corresponding to a
single energy deposition in the detector. We demonstrate that events not
belonging to this category are discarded with an efficiency above 99.8%, with a
minimal loss of $^{163}\mathrm{Ho}$ events of about 0.7%. While the filter
using the trigger time information is completely energy independent, a slight
energy dependence of the filter based on the time profile is precisely
characterised. This data reduction protocol will be important to minimise
systematic errors in the analysis of the $^{163}\mathrm{Ho}$ spectrum for the
determination of the effective electron neutrino mass.
