DIXON NIPPLE 3/4X3/4 TN66|Nylon fittings are generally acceptable for working pressures up to 150 PSI at normal room temperatures. At very low pressures, temperatures can approach 175° with no degradation of the fittings strength. Nylon fittings should not be used with acid-based fertilizers, bromine, chlorine, fluorine, hydrochloric acid, iodine, nitric acid, phosphoric acid, sulfuric acid or xylene. They also should not be used with compressed gas.