Ko te anga me te ngongo whakawhiti wera te nuinga o te anga, te paihere ngongo, te pepa ngongo me te upoko. I roto i era, ka rere tetahi wai (he wai makariri ake) ki te taha ngongo, ko tetahi atu wai (he wai wera ake) ka rere ki te taha anga. Nā te rerekētanga o te pāmahana i waenga i ngā mea e rua, ka whakawhitia te wera mai i te wē pāmahana teitei-ki te wē pāmahana iti-, mā reira ka puta te whakawhiti wera.
Inaa, ka uru te wai wera ki te taha anga, ka whakawhitia tona wera ki te wai matao i te taha ngongo ma te pakitara ngongo. Ko tenei tikanga whakawhiti wera ehara i te mea pai anake, engari ka taea hoki te whakahaere i te pāmahana o te wai. I tua atu, ka taea hoki te hoahoa te anga me te ngongo whakawhiti wera hei hanga -paahi, maha ranei-i runga i nga tino hiahia ki te whakatutuki i nga whakaritenga whakawhiti wera rereke.