Combi boiler DHW priority questions in Greater Vancouver

Domestic hot water, or DHW, priority is a defining feature of how a combi boiler behaves: it puts your taps ahead of your radiators. Homeowners often have questions about what that means day to day. Here is a practical guide to DHW priority for Greater Vancouver homes.

What DHW priority means

When you open a hot tap, the combi immediately switches its full output to heating that water, pausing central heating until you are done. This DHW-priority logic ensures your shower or tap always gets the boiler's full capacity, which is what makes on-demand hot water feel responsive.

Because the boiler dedicates itself to one job at a time, hot water is consistent at a single outlet but its capacity is shared if you open several hot taps at once. Understanding this helps set expectations in busier households around the Lower Mainland.

• Hot taps take priority over radiators automatically
• A single outlet gets the boiler's full hot-water output
• Running multiple hot taps divides that capacity
• Heating resumes as soon as the hot tap closes

Living with DHW priority

For typical use, DHW priority is invisible and simply works. If you find hot water weakening when two showers run together, that is the shared-capacity effect, not a fault, and staggering use solves it. The home's heating barely notices the short pauses during normal hot-water draws.

If hot water is inconsistent at a single tap, that is different from priority behaviour and may indicate a scaled heat exchanger, a low-flow trigger issue, or a diverter problem, all worth a professional check. Households that genuinely need simultaneous high hot-water demand can ask a technician whether a different setup suits them better; efficient combi upgrades may qualify for FortisBC and CleanBC rebates, which a technician can confirm.

• Stagger showers if capacity feels divided
• Single-tap inconsistency points to a fault, not priority
• Have scaling, flow, or diverter issues checked professionally
• Ask about options and possible rebates for high-demand homes

Frequently Asked Questions

What is DHW priority on a combi boiler?

It means the boiler puts domestic hot water ahead of central heating, pausing the radiators while a hot tap runs so your taps always get full capacity.

Why does my hot water drop when two taps run?

DHW priority gives the full output to hot water, but that capacity is shared across outlets, so two simultaneous hot taps each get less. Staggering use fixes it.

Does DHW priority hurt my heating?

Not noticeably. The pauses during normal hot-water draws are short, and radiators hold heat well, so rooms stay comfortable.

My single shower runs hot then cold. Is that priority?

No. Inconsistency at one tap usually points to scaling, a flow-trigger issue, or a diverter fault rather than priority, and a technician should inspect it.

HeatLand Heating & Cooling is a licensed and insured, TSBC-certified HVAC company serving homeowners across Greater Vancouver. Our technicians diagnose the real fault, explain your options in plain language, and complete the work safely and to code.

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