Canada-wide water heater information · On-site service in Metro Vancouver, BC
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Comparison
Verdict in brief
The two smallest tanks in Giant's Canadian atmospheric-vent line differ by 10 US gallons and 8,000 BTU/h: the UG30 stores 30 US gal (114 L) on a 32,000 BTU/h input, the UG40 stores 40 US gal (151 L) on 40,000 BTU/h, both on natural gas or propane. The extra capacity and the faster burner compound, so the UG40 is not simply a bigger UG30. Giant publishes neither a first-hour rating nor an energy factor for either model, so the gallon label alone cannot size them; that is decided by a hot-water demand assessment.
Published manufacturer figures with units. Storage and flow figures are different measures and are shown on their own rows; blanks mean not applicable or not published.
| Specification | Giant UG30Gas storage tank | Giant UG40Gas storage tank |
|---|---|---|
| Storage capacity | 30 US gal (114 L) | 40 US gal (151 L) |
| Input, natural gas | 32,000 BTU/h | 40,000 BTU/h |
| Type of gas | Natural gas (N) or propane (LP) | Natural gas (N) or propane (LP) |
| Venting | Atmospheric; air is drawn from inside the home and exhaust vents into a chimney | Atmospheric; air is drawn from inside the home and exhaust vents into a chimney |
| Warranty (Giant published) | 6 years against inner tank leakage; 6 years on component parts, from the date of installation | 6 years against inner tank leakage; 6 years on component parts, from the date of installation |
| Certification | CSA reference published by Giant; EnerGuide referenced on the same page | CSA reference published by Giant; EnerGuide referenced on the same page |
“—” means not applicable to that system type or not published by the manufacturer. Flow figures are only comparable at the same temperature rise; UEF values are only comparable within the same draw pattern.
Both tanks are the same family with the same feature set: a glass-lined inner tank, Giant's FVIR flammable-vapour-ignition resistance, a heavy-duty magnesium anode rod, a turbulator dip tube to reduce sediment build-up, a front-positioned gas valve and a thermopile pilot with a piezoelectric push-button igniter. The difference is storage and burner size, and the two reinforce each other: the UG40 holds a third more water and heats it 25% faster, so under a sustained draw it holds temperature longer rather than just starting with more.
Giant's Canadian product page gives capacity and input but does not publish a first-hour rating, recovery rate, energy factor or dimensions for either model, so WaterHeating.ca does not state those figures. That matters for the choice: a 30-gallon tank and a 40-gallon tank with unknown recovery rates cannot be ranked from the label alone, and the correct step is a demand assessment against the busiest hour of the household, not a guess from the tank size.
Both are atmospheric units. They draw combustion air from inside the home and exhaust by natural draft into a chimney or B-vent, so they need a sound flue and room air, and they cannot be side-wall vented. Where the chimney is gone, shared or a sealed mechanical room is planned, the right families are Giant's power-vent or power-direct-vent models, which use ULC S636 plastic pipe to a wall or roof.
One practical difference from many current tanks is electrical dependence. Giant lists a thermopile pilot and push-button igniter for this family, so neither the UG30 nor the UG40 needs a standing 120 V supply to light or run, and both keep making hot water through a power outage. A power-vent or fan-assist model in the same size class does not. Both carry Giant's published 6-year inner-tank and 6-year parts warranty from the date of installation, with conditions in the owner's manual.
Giant · Gas storage tank
The Giant UG30 is a 30 US gallon (114 L) atmospheric-vent natural gas or propane storage water heater with a 32,000 BTU/h input, a glass-lined tank, FVIR technology and a 6-year tank and parts warranty, made in Canada by Giant.
Giant · Gas storage tank
The Giant UG40 is a 40 US gallon (151 L) atmospheric-vent natural gas or propane storage water heater with a 40,000 BTU/h input, a glass-lined tank, FVIR technology and a 6-year tank and parts warranty, made in Canada by Giant.
It is the same family with more storage and a larger burner: 40 US gal (151 L) on 40,000 BTU/h against 30 US gal (114 L) on 32,000 BTU/h. Because it both stores and recovers more, the gap under load is larger than the gallon difference suggests. Giant does not publish a first-hour rating for either, so sizing is confirmed in a demand assessment.
No standing electrical supply is required for the pilot. Giant lists a piezoelectric push-button igniter and a thermopile pilot design for the atmospheric family, which light and run the pilot without mains power, so hot water continues during an outage. The instruction manual governs the installed unit.
The UG30 suits a small, low-demand home such as a suite or laneway house; the UG40 suits two to four people with moderate simultaneous use. Both need a working chimney or B-vent and room combustion air, and both should be confirmed against the household's peak hour before ordering.
A consultation includes a hot-water demand review so capacity is right for your winter, not the brochure's.
On-site service in Metro Vancouver, BC. Call to check availability.
Sources and verification
Facts checked September 21, 2026. Last updated September 21, 2026. Technical reviewer: not yet assigned.