Technical heating guide
Boiler Pressure Problems
Pressure that rises, drops, or causes relief-valve discharge can point to expansion control, fill-valve, leakage, trapped air, heat-exchanger, or system-temperature problems.
Safety: Do not open gas-fired equipment, alter gas settings, bypass safeties, or work inside electrical controls without the proper qualification. For a gas smell or CO alarm, leave and call the utility or 911 from outside.
Pressure rising when hot
A failed, isolated, undersized, or incorrectly charged expansion tank can allow pressure to climb as system water expands.
Pressure falling
Loss of pressure may come from visible leaks, relief-valve discharge, air elimination, hidden piping leakage, or an issue with the automatic fill arrangement.
Do not treat the gauge alone
The gauge, expansion tank, fill pressure, system height, water temperature, and relief valve all need to be considered together.
What to send before the visit
- Clear photo of the rating plate and model number
- Photo or exact wording of any error code
- Whether the issue affects space heating, hot water, or both
- When the problem started and whether a reset temporarily restores operation
- Your city and preferred service timing
Need service? Call 647-699-2474 or use the request form. Heating Experts will confirm the diagnostic visit and review repair pricing before approved work begins.
Technical service standards
Technical resources
Understand the system before approving the repair.
Use our knowledge hub for plain-language explanations of boiler lockouts, pressure problems, hydronic flow, combustion testing, condensate faults, OEM parts, and maintenance planning.