Ukumisela ubukhulu bodonga lwe-3/16 ye-tubing, kufuneka sazi i-diameter yangaphandle (OD) kunye ne-diameter yangaphakathi (ID) ye-tubing. Ukuba i-diameter yangaphandle yi-3/16 "kwaye akukho lwazi luthile lunikezelwayo malunga nobubanzi bangaphakathi, asikwazi ukubala ngokuchanekileyo ubukhulu bodonga. Ubukhulu bodonga bunokwahluka ngokuxhomekeke kuhlobo oluthile lwetyhubhu kunye nemigangatho yokuvelisa.