Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The Weil-McLain SVF 725 and Weil-McLain SVF 850 are both condensing boilers in the Weil-McLain SVF (Stainless Vertical Firetube) line. The Weil-McLain SVF 725 is rated 725 MBH input, 708 MBH gross output and 97.7% thermal efficiency, and the Weil-McLain SVF 850 is rated 850 MBH input, 829 MBH gross output and 97.5% thermal efficiency. Weil-McLain SVF 850 lists 125 MBH more input than Weil-McLain SVF 725 (850 MBH against 725 MBH). Weil-McLain SVF 725 carries the higher published thermal efficiency at 97.7%, against 97.5%. Both list the same published shipping weight of 675 lb.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Weil-McLain SVF 725 | Weil-McLain SVF 850 |
|---|---|---|
| Maximum input | 725 MBH | 850 MBH |
| Gross output | 708 MBH | 829 MBH |
| Thermal efficiency | 97.7 % | 97.5 % |
| Turn-down ratio | 10:1 | 12:1 |
| Domestic hot water | Heating-only commercial boiler — domestic hot water comes from a separate indirect tank or water heater | Heating-only commercial boiler — domestic hot water comes from a separate indirect tank or water heater |
| Approximate shipping weight | 675 lb | 675 lb |
| Length x width x height | 42.2" x 24.9" x 49.8" | 42.2" x 24.9" x 49.8" |
| Air intake / exhaust vent diameter | 6" | 6" |
| Supply / return water connections | 2-1/2" NPT | 2-1/2" NPT |
| Gas connection size | 1-1/4" NPT | 1-1/4" NPT |
| Fuel | Natural gas | Natural gas |
| Net AHRI rating | 616 MBH | 721 MBH |
| Maximum working pressure | 160 psi | 160 psi |
| Control | Unity 2.0 color touchscreen Nuro controls | Unity 2.0 color touchscreen Nuro controls |
Published ratings: the Weil-McLain SVF 725 is rated 725 MBH input, 708 MBH gross output and 97.7% thermal efficiency; the Weil-McLain SVF 850 is rated 850 MBH input, 829 MBH gross output and 97.5% thermal efficiency. Weil-McLain SVF 850 lists 125 MBH more input than Weil-McLain SVF 725 (850 MBH against 725 MBH). Weil-McLain SVF 725 carries the higher published thermal efficiency at 97.7%, against 97.5%.
The turndown differs: the Weil-McLain SVF 725 lists 10:1, while the Weil-McLain SVF 850 lists 12:1.
Both records print the same domestic-hot-water arrangement (Heating-only commercial boiler — domestic hot water comes from a separate indirect tank or water heater), shipping weight (675 lb), dimensions (42.2" x 24.9" x 49.8") and venting (6"), per the cited sources.
Weil-McLain
The Weil-McLain SVF 725 is a current commercial stainless-steel vertical fire-tube condensing boiler: 725 MBH maximum input, 708 MBH gross output and a 616 MBH net AHRI rating at 97.7% thermal efficiency, with a 10:1 turn-down, 2-1/2" NPT supply/return, 1-1/4" NPT gas and a 6" vent connection.
Weil-McLain
The Weil-McLain SVF 850 is a current commercial stainless-steel vertical fire-tube condensing boiler: 850 MBH maximum input, 829 MBH gross output and a 721 MBH net AHRI rating at 97.5% thermal efficiency, with a 12:1 turn-down, 2-1/2" NPT supply/return, 1-1/4" NPT gas and a 6" vent connection.
The Weil-McLain SVF 850 lists 850 MBH, against 725 MBH on the Weil-McLain SVF 725, per the cited documentation.
The Weil-McLain SVF 725 carries the higher published thermal efficiency at 97.7%, against 97.5%.
A consultation includes a heat-loss review so the size is right the first time.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.