The boiler's fall start-up is a sequence you can walk before the first cold week. Walk the room in the same order each year, and write down what you see. The notes are what make the age of the boiler useful for planning.
Start with the gauge
Note where the pressure gauge sits when the system is cold and again when it is running. Write both readings in a small notebook or on a card taped inside the boiler room door. A needle that sits differently than it did last season is worth a call. The markings on the gauge show the range the maker intends, so use those markings rather than a figure from memory.
Walk the perimeter
Look at the floor under the boiler, the valve fittings, the expansion tank connection, and the pipe joints nearby. Look for drips, staining, or white mineral crust. Listen while the system runs for knocking, gurgling, or hissing. Note what you hear and when, and mention it to the service provider at the next visit.
Check the relief valve discharge
The pressure relief valve has a discharge pipe that carries hot water to a safe place near the floor. Confirm the pipe is in place, runs down and out to where the maker's instructions direct, and is not plugged or dripping. Do not cap, reroute, or adjust the valve yourself. If it is dripping or the pipe is blocked, call a qualified service provider.
Radiators and clear space
If your system has radiators with bleed valves, walk the house and note any that run cool at the top. Bleeding air from radiators is an owner task on many systems, and your installer can show you the method. Keep the space around the boiler clear of stored boxes, paint, and fuel containers, so service access stays open and combustion air is not blocked.
Safety you should not skip
Keep a working carbon monoxide alarm in or near the boiler room and test it at the start of the season. If you smell gas or see soot around the boiler, leave the area and call for service from outside the house.
What stays with the pro
Gas line work, burner adjustment, controls, the flue, the pressure relief valve itself, and any flushing or chemical treatment belong to a qualified service provider. An annual service visit is the place to have the boiler checked as a whole system. Bring your notes from the gauge and the walk.
The typical service life and planning window for a boiler are on the Boiler page. Use your gauge log and service visits to decide when that timing matters for your house.