Advice
Combi Boiler Flow Rate Explained
The number that decides whether two showers can run at once.
A combi boiler's hot water flow rate — measured in gallons or litres per minute at a given temperature rise — determines how much hot water it can deliver at once. It's the key spec for homes that run multiple hot taps or showers simultaneously.
Choosing enough flow rate for your household avoids the disappointment of weak or fluctuating hot water.
What affects flow rate
- The boiler's BTU/kW output
- Incoming water temperature (colder in winter = lower rate)
- Number of simultaneous hot water draws
- Incoming mains pressure
- Desired hot water temperature
Sizing for demand
A single-bathroom condo needs far less flow than a busy family home with multiple showers. We size flow rate to your peak simultaneous demand.
This is not a DIY repair
Combi boilers are gas-fired appliances regulated under the BC Safety Standards Act. Opening the unit, touching the gas valve, or working on the flue without a valid BC gas-fitter licence is both unsafe and illegal. Diagnosing the fault is helpful — fixing it should always be left to a certified technician.
Call 778-909-5731More advice & guides
Talk to a Licensed Combi Boiler Specialist
Free, no-obligation quotes across Greater Vancouver. CombiBoiler.ca — A division of ROMA Heating Ltd..