Ko te DN (Nominal Diameter) ko te diameter ingoa o te paipa, ko te toharite o te diameter o waho me te diameter o roto. Te uara o DN =te uara o De -0.5*te uara o te matotoru pakitara ngongo. Tuhipoka: Ehara tenei i te diameter o waho me te diameter o roto.

Ko te wai, te paipa rino tuku hau (pupa maitai piauau, putorino maitai kore ranei), paipa rino maka, putorino hiato maitai-kirihou me te putorino polyvinyl chloride (PVC), me etahi atu, me tohuhia te diameter ingoa "DN" (penei i te DN15 , DN50).

De (Diameter waho) te tikanga o te diameter o waho o te putorino, PPR, PE putorino, polypropylene pipe waho diameter, te tikanga tohu ki De, a me tohu katoa rite te puka rite te diameter waho * matotoru taiepa, hei tauira De25 × 3 .

D te tikanga e tohu ana ki te diameter o roto o te putorino.

d te tikanga e pa ana ki te diameter o roto o te paipa raima. Ko nga paipa raima (he raima ranei), he paipa uku, he paipa uku-waikawa, he taera rango me etahi atu paipa, me tohu te diameter o roto o te putorino d (pērā i te d230, d380, etc.)

Ko te Φ e tohu ana i te diameter o te porowhita noa; ka taea hoki te tohu i te diameter o waho o te putorino, engari i tenei wa me whakanuia e te matotoru o te pakitara.