Lochinvar SQUIRE and Triangle Tube Smart Series are the two best-known indirect-fired water heater lines in the US residential market. Both are paired with hydronic boilers and heated via internal heat exchanger coil.
Side-by-side
| Lochinvar SQUIRE | Triangle Tube Smart | |
|---|---|---|
| Tank construction | SIT: glass-lined / SSU: stainless | Tank-in-tank stainless |
| Heat exchanger design | Coil inside tank | Inner stainless tank acts as exchanger |
| Anode rod | SIT: required / SSU: none | None (stainless) |
| Warranty residential | SIT: 10-yr / SSU: Lifetime | Lifetime |
| Heat transfer efficiency | Coil-to-water | Tank-shell-to-water (more surface area) |
| Sizing range | 40-120 gal SIT / 45-80 gal SSU | 30-119 gal Smart |
| Price range (residential) | $1,199-2,899 | $1,800-3,500 |
The tank-in-tank advantage (Triangle Tube)
Triangle Tube Smart uses a unique tank-in-tank design — boiler water fills the outer shell; domestic water fills the inner stainless tank. The inner tank itself is the heat exchanger. This provides:
- Much larger heat transfer area than a coil design
- Faster recovery (often 20-30% better FHR)
- No coil scaling concerns (boiler water fills the surrounding space)
- All-stainless construction = no anode rod ever
Where Lochinvar SQUIRE leads
- Lower upfront cost — SIT 65-gal $1,399-1,799 vs Smart 60-gal $2,200-2,800
- Wider contractor availability — more installers familiar with SQUIRE
- SIT 10-year warranty sufficient for most municipal-water installs
- SSU stainless option matches Triangle Tube\'s lifetime warranty at lower cost
- Larger sizes available — SIT120 for high-demand residential
Where Triangle Tube leads
- Higher recovery rate from tank-in-tank design
- Stainless construction throughout — no anode rod regardless of size
- Lifetime warranty standard on all residential models
- Cleaner long-term operation — no anode rod degradation byproducts
Cost comparison (65-gallon equivalent installed)
- Lochinvar SIT065: $2,200-3,200 installed
- Lochinvar SSU80: $3,200-4,400 installed
- Triangle Tube Smart 60: $2,800-3,800 installed
Which to choose
- Budget-priority residential, soft-to-moderate water: Lochinvar SIT
- Premium stainless, lifetime warranty, no maintenance: Lochinvar SSU OR Triangle Tube Smart
- Highest recovery rate from a modest-size tank: Triangle Tube Smart
- Lochinvar boiler already + want single-brand ecosystem: SQUIRE
- Well water with aggressive chemistry: Lochinvar SSU or Triangle Tube
Bottom line
Both excellent indirect tank lines. SQUIRE SIT wins on budget; SQUIRE SSU and Triangle Tube Smart compete head-to-head on stainless premium. Triangle Tube\'s tank-in-tank design has a recovery-rate edge; Lochinvar has the wider distribution and contractor familiarity.