BoilerBuying Guide2026-03-10
Do Combi Boilers Need a Water Tank?
No — combis heat water on demand, so they need no hot-water cylinder or cold tank.
One of the combi's big advantages is eliminating tanks. Here's how it works.
On-demand hot water
A combi heats water instantly as it flows, so there's no need for a stored hot-water cylinder or a cold-water tank in the loft.
The benefit
This saves space, removes standby heat losses, and means you never run out of hot water within the unit's flow rate.
Key takeaways
- No cylinder or cold tank needed
- Heats water on demand
- Saves space
- No standby losses
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