Start at the boiler with the clipboard. Find the pressure gauge on the front or top of the unit. The needle sits inside a band printed on the dial, and that band is your reference. Everything in this walk-through is about what the needle, the pipes, the rooms and the floor do over time, and what you write down about each one.

Log the pressure while the system is cold

Read the gauge before the first heating call of the day, while the system is cold. Write the number down with the time and the date on the same sheet. Read it the same way each visit so the readings can be compared. The label on the unit or the installer's sheet gives the cold fill range. Copy that range to the top of your log so you do not have to look for it later.

A reading that drifts slowly down across a season is worth noting, even if the needle is still inside the band. A reading that keeps needing a top-up is worth a call to a licensed heating technician. Do not keep adding water by feel and hope the trend stops. Ask the technician to check the fittings, the fill valve and the expansion tank for leaks or a setting that has moved.

Listen to the pipes at startup and shutdown

Stand in the room with the boiler and let it run through a full call for heat. Note any banging, ticking, knocking or gurgling. Record when it happens: at startup, during the run, or as the unit shuts down. Record how long the sound lasts and which zone or room it seems to come from. Plain words are enough, such as sharp knock at startup in the back bedroom zone.

Each sound has causes a technician can name, including trapped air, mineral build-up, or a pump that is struggling. You are not diagnosing the sound. You are giving the technician a dated record that is easier to act on than a memory.

Watch how the rooms come up to temperature

Compare how long the house takes to reach the set temperature now with what your earlier notes say. Pay attention to a room that stays cool while the others heat, and to radiators that run warm at the bottom but stay cool at the top. These patterns are early signs that the water is not moving through the loop as well as it did. Write down which rooms are affected and whether the pattern is steady or comes and goes.

Check the floor, the fittings and the relief line

Look at the base of the boiler, at each pipe union, and at the pipe that runs from the relief valve. Look for dry staining, a bead of water on a joint, or a light crust of mineral deposit around a fitting. Wipe a dry paper towel across any spot you are unsure of, then check it again at the next visit. Mark the spot on your log.

Do not cap, plug or redirect the relief valve discharge pipe. If you see water coming from it, describe what you saw and call a licensed technician.

Note the colour of the water you add

When you do add water, look at the water in the fill container or the first few seconds from the fill point. Cloudy or rust-coloured water is worth writing down with the date. It does not tell you the cause by itself, but it gives the technician a clue to check.

Check the carbon monoxide alarm

Confirm that a working carbon monoxide alarm is installed in the same space or the nearest area that serves the boiler, and that its test function works. Write the check on the same sheet as the pressure log. This is a routine safety check you can make yourself at each visit.

What to ask the technician

  • Which cause does my pressure log point to, and what would confirm it?
  • Is the expansion tank pressure set for this system and this house?
  • Does the pressure trend need a leak test at the fittings and fill valve?
  • What is making the sound I logged at startup, and does it change over the run?
  • Which zones are slow to heat, and does the pattern match the loop or the valves?
  • What should I keep logging until the next visit, and what would make you want to see the unit sooner?

Where the planning figures are

The boiler page on this site shows typical service life and when to plan, and it is the place to turn the install year on your sheet into a planning date. Use your log to decide when to ask for a fuller assessment, and use the page to decide when to start comparing options. A changing unit is a planning input. It is not a reason to panic, and the log is what lets you plan calmly.