How a Boiler Works in a House (And 5 Things That Kill It), by The Cutaway House on YouTube. 3 min 35 s.
- Video length
- 3 min 35 s
- Time to do it
- 30 minutes
- Difficulty
- Easy
- Steps
- 8
What you need
Steps
Read the pressure gauge on the boiler when the system is cold. A typical hot water system sits at about 12 to 15 psi (0.8 to 1.0 bar). Top up through the fill valve only if it reads lower.
Bleed air at the radiators, starting on the lowest floor. Let the boiler cool first, then open each bleed valve with a key until water runs steady with no hiss.
If the relief valve is dripping, look at the expansion tank. A waterlogged tank lets pressure climb to 30 psi and the valve dumps water to protect the boiler.
Never cap or plug the 30 psi (2.1 bar) relief valve. If it keeps dumping water after the tank is checked, call a technician.
If one room stays cold while the boiler runs, check the circulator pump. A stuck pump often needs freeing or replacing by a pro.
If the boiler will not light, look for a lockout code and check for a blocked vent. Reset once, then call a technician.
Banging or kettling means sludge and scale in the system. Book a flush and service rather than turning the temperature up.
If you leave the house in winter, keep the thermostat at 55 °F (13 °C) or more so pipes do not freeze.
Tips and common mistakes
Bleed the lowest radiators first so trapped air moves upward and out.
Water leaves the boiler at up to about 180 °F (82 °C), so let it cool before opening any valve.
Put CO alarms outside every sleeping area and on every level of the home.
If you smell rotten eggs, get everyone out and call the gas company from outside.
Questions
What pressure should my boiler be at?
When cold, most hot water systems run at about 12 to 15 psi (0.8 to 1.0 bar). Much higher than that points to a fill valve or expansion tank problem.
Why is water coming out of the relief valve?
The valve opens at 30 psi (2.1 bar) to protect the boiler. A waterlogged expansion tank or an overfilled system is the usual cause.
Can I bleed radiators while the heating is on?
No. Wait until the system has cooled down, because the water is scalding and the pump can pull in more air while running.
This guide was drafted from the video's details and general task knowledge. It has not been checked against the full video. Check the video and relevant product instructions before following a procedure. Report a correction.
