Honeywell ISO-UNIT 1" NPT sealing union

This sealing union, the Honeywell ISO-UNIT in 1" NPT, is a fitting designed to create a leak‑tight joint that can be readily disconnected for servicing. In a heating system such unions are typically used at points where a component – for example a sensor pocket, a pressure gauge or a shut‑off valve – must be removable without disturbing the permanent pipework. The 1" NPT female threads mate with standard iron or steel pipe nipples. Parts of this type are selected primarily by thread size and connection style. NPT threads are tapered and rely on a thread sealant or PTFE tape to achieve a tight seal. When replacing a sealing union, check that the thread size matches the existing pipe; also verify that the union is designed for the working pressure and fluid temperature of the system (water, gas or oil). The union body may be brass, steel or stainless steel; the selection depends on the fluid and the environment. No compatibility with specific boiler models or brands can be stated for this article from the data provided. This product appears under the Sensor components category in the catalogue. In many installations a sealing union is used to mount an immersion pocket or a thermowell, which then houses an NTC sensor. The union allows the sensor to be withdrawn without draining the system. However, the specific application of this Honeywell ISO‑UNIT 1" NPT union is not defined further by the available data. For correct installation, always follow the manufacturer’s instructions for torque and sealant.