Simple distillation methods can be appropriate where expected usage is low and capital cost considerations outweigh running cost considerations.

Small single-effect stills evaporate the feedwater in a single stage, separate the pure dry steam from the impurities entrained in the water vapour, then condense the pure steam to WFI. There is no further energy recovery, utility consumption (especially cooling water) is high.

An alternative method is to couple a condenser unit to a pure steam generator, arriving at the same result, but with the benefit of useful pure steam generation (e.g. for sterilisation) when WFI is not being produced.
The both cases the quality of the distillate is not compromised, divert valves ensure any out-of-spec production is diverted to drain.