The Triangle Tube Smart Indirect is the brand's flagship indirect-fired water storage tank, engineered to pair with Triangle Tube Prestige condensing boilers (or any compatible primary boiler) for high-efficiency domestic hot water production. The "Smart" name refers to the heat exchanger design: a tank-within-a-tank construction that achieves higher heat transfer efficiency than traditional coil-in-tank indirects.
Tank-in-tank construction
Unlike conventional indirect tanks where a coiled tube inside the tank carries boiler water and transfers heat to surrounding potable water, the Smart Indirect uses an inner tank holding the potable water surrounded by an outer tank carrying boiler water. The result is significantly more heat transfer surface per tank volume — Smart Indirect 40 has roughly 4x the effective heat exchange surface of a same-capacity coil-in-tank design. Translation: faster recovery, smaller boiler can support the same domestic load, lower part-load standby losses.
Sizing across the lineup
Smart Indirect models include the Smart 30, Smart 40, Smart 50, Smart 60, Smart 80, and Smart 110. The Smart 40 is the most-specified residential pairing for 2–4 bath homes with a Prestige 110 or 175 boiler. Smart 80 handles 4+ bath homes or homes with whirlpool tubs / large soaking tubs.
Prestige boiler pairing
Smart Indirect tanks are engineered for Prestige condensing boilers but compatible with any boiler in the 30,000–250,000 BTU/hr range with proper primary loop sizing. With a Prestige Solo 110 paired to a Smart 40, recovery from cold is approximately 90 minutes; from depleted at 120°F setpoint about 25 minutes back to setpoint. The matched-pair installation pulls maximum efficiency from both components.
Why some installers specify Smart over coil-based
- Recovery rate: tank-in-tank delivers faster recovery for same boiler size
- Standby losses: lower because of better insulation envelope and tank construction
- Service access: water-side and boiler-side easily isolatable for service
- Cleaning: domestic side does not collect scale on a coil; it collects on a smooth inner tank wall that flushes more completely
Installation and primary loop
Install procedure: primary connections (1" NPT typical) to the boiler-side outer tank, domestic connections (3/4" NPT) to the inner tank, expansion tank on the cold inlet, T&P relief valve, circulator on the primary loop (or integrated into boiler), aquastat sensor at the tank well. The Smart Indirect has sensor wells optimized for the Prestige boiler's DHW priority logic — the boiler's control communicates with the tank directly via temperature sensor reading.
Warranty and lifespan
Smart Indirect carries a 15-year tank warranty (residential) and the typical glass-lined tank lifespan of 20–25 years with proper maintenance. The aluminum-zinc anode rod requires inspection at year 5 and replacement when 75% consumed; anode rod port is at the top with easy access. Annual maintenance includes T&P testing and flush; no specialty maintenance beyond standard residential tank practices.