DN (Nominal Diameter) zvinoreva dhayamita rezita repombi, inova avhareji yedhayamita rekunze nedhayamita remukati. Kukosha kweDN = kukosha kweDe -0.5* kukosha kwechubhu rusvingo ukobvu. Cherechedza: Iyi haisi iyo dhayamita yekunze kana dhayamita yemukati.

Mvura, gasi kutapurirana simbi pombi (galvanized simbi pombi kana non-galvanized simbi pombi), cast iron pombi, simbi-plastiki composite pombi uye polyvinyl chloride (PVC) pombi, etc., inofanira kunyorwa zita dhayamita "DN" (senge DN15, DN50).

De (External Diameter) zvinoreva dhayamita rekunze repombi, PPR, PE pombi, pombi yepolypropylene yekunze dhayamita, kazhinji yakatemwa neDe, uye zvese zvinofanirwa kutara sechimiro sedhayamita rekunze * ukobvu hwemadziro, semuenzaniso De25 × 3.

D kazhinji inoreva dhayamita yemukati yepombi.

d kazhinji inoreva dhayamita yemukati yepombi yekongiri. Yakasimbiswa kongiri (kana kongiri) pombi, ivhu pombi, asidhi-resistant ceramic pombi, humburumbira mataira uye dzimwe pombi, ane pombi dhayamita inofanira kumiririrwa mukati dhayamita d (senge d230, d380, nezvimwewo)

Φ inomiririra dhayamita yedenderedzwa rakafanana; inogonawo kumiririra dhayamita yekunze yepombi, asi panguva ino inofanira kuwedzerwa nehupamhi hwemadziro.