Triangle Tube Water Heater Problems: Smart and Prestige
On this page (8 sections)
The Short Answer: Most Triangle Tube “water heaters” are Smart indirect tanks heated by a boiler, or Prestige/Excellence condensing boilers that also make domestic hot water. If the boiler is running but the water is cold, the problem is usually the tank’s call for heat: the sensor or aquastat, the circulator or zone valve, or domestic-hot-water priority. Lockouts and leaks are separate problems, and each one has a different fix.
First, identify which Triangle Tube you have
The rating plate tells you, and the answer changes everything below.
- Smart series (SMART 30 through SMART 120 class): a floor-standing indirect tank with no burner of its own. It uses a tank-in-tank design: boiler water fills the outer shell and heats a stainless inner tank that holds your domestic water. No pilot, no gas valve, no flash codes on the tank itself.
- Prestige, Prestige Excellence, Instinct, Challenger: wall-hung gas condensing boilers with a display. Excellence and combi versions make domestic hot water on demand through an internal plate heat exchanger; others heat an indirect tank such as a Smart.
If you have a gas-fired storage tank from another maker, this page does not apply; see HTP Phoenix problems or the general no hot water guide.
What the symptom points to
| What you notice | Likely cause | How urgent |
|---|---|---|
| House heat works, tank water cold (Smart) | Tank is not calling for heat: sensor or aquastat, circulator, zone valve, or priority setting | Same week; no hazard |
| Hot at the tank, lukewarm at taps | Mixing (anti-scald) valve or recirculation return set up wrong | Not urgent |
| Combi: heating works, showers cold or weak | Diverter (3-way) valve, domestic flow sensor, or scale in the plate exchanger | Same week |
| Boiler display shows a lockout | Ignition, flame, vent or condensate fault | Do not keep resetting; call a technician if it repeats |
| Boiler pressure keeps rising, boiler relief valve drips | Possible leak from the domestic inner tank into the boiler loop | Prompt service |
| Water under a Smart tank with all fittings dry | Tank shell or inner tank failure | Replacement |
| Tank relief (T&P) valve dripping | High water pressure, thermal expansion, or a worn valve | Prompt service; never cap it |
Why a Smart tank stops getting hot
An indirect tank only heats when its control asks the boiler for heat and boiler water actually flows through the outer shell. The common breaks in that chain are a temperature sensor that has slipped out of its well (so the control misreads the tank), a circulator or zone valve that no longer opens, and domestic-hot-water priority switched off or reconfigured after a thermostat or control change. Air in the boiler loop after work on the heating system can also stop flow through the tank.
A tank that reaches temperature but delivers lukewarm water at the taps usually points to the mixing valve on the hot outlet, not to the tank. Indirect tanks are often stored hotter than tap temperature, with a mixing valve bringing it down; when that valve sticks, it looks like the tank has failed.
Prestige and Excellence lockouts
Condensing boilers produce acidic condensate continuously while firing. A blocked trap, a failed condensate pump, a frozen outdoor drain, or a blocked intake or exhaust pipe will make the boiler shut down and display a fault. Ignition and flame faults are a separate group. Code numbers and wording differ by generation and control, so read the code from the display and look it up in the manual for your model before acting.
On Excellence and other combi models, a boiler that heats the house well but cannot hold shower temperature often has scale in the domestic plate heat exchanger, or a diverter valve that is not moving fully to the domestic side.
What you can check safely
- Photograph the display or fault code before resetting anything.
- Confirm the boiler has power and the gas supply valve is open, and that other gas appliances work.
- Look at the domestic hot water setpoint and any summer or heating-only mode on the boiler control.
- Check whether every fixture is affected or only some (one cold shower usually means its own mixing valve).
- On a boiler with an external condensate line or pump, check whether the line is kinked, frozen, or the pump reservoir is overflowing.
- Check that outdoor intake and exhaust terminations are clear of snow, leaves, or nests.
- If a lockout reset is described in your owner’s manual, use it once. If the code returns, leave the boiler off and call for service.
What the technician will check
On a Smart tank, a heating technician will confirm whether the tank is actually calling for heat, whether boiler water reaches it, and whether the sensor or aquastat reads correctly. They will check pump and zone-valve operation, priority settings, and air in the loop. If boiler pressure has been climbing, they will isolate the tank to test whether domestic water is leaking into the boiler side through the inner tank.
On a Prestige or combi, they will read the fault history, check combustion, the condensate path, venting, gas supply pressure against the rating plate, and the domestic flow sensor and diverter valve. Descaling a plate exchanger needs isolation valves and the manufacturer’s procedure.
Repair or replace
Sensors, aquastats, circulators, zone valves, mixing valves, and relief valves are part replacements. Scaled plate exchangers can often be cleaned. A Smart tank that leaks from the shell, or whose inner tank leaks into the boiler loop, has to be replaced. Patching or adding sealants is not a repair. A wet floor under an indirect tank can also come from fittings or the relief valve, so confirm the source first; water leaking from the bottom of a tank covers how to tell.
If the relief valve on the tank is the one dripping, relief valve leaking on a new heater and expansion tank full of water explain the pressure side.
Frequently Asked Questions
Q: Does a Triangle Tube Smart tank have an anode rod to replace? A: The Smart series uses a stainless inner tank and is not designed around a sacrificial magnesium anode the way glass-lined tanks are. Check the manual for your model before removing any plug.
Q: Why does my boiler pressure go up when the Smart tank is installed? A: Domestic water pressure is usually higher than boiler pressure. If the inner tank develops a leak, house water pushes into the boiler loop, the pressure climbs, and the boiler relief valve may discharge. A technician can confirm this by isolating the tank.
Q: Can I descale a Prestige Excellence myself? A: Only if your owner’s manual assigns it to the owner and the unit has service valves. Running acid through the domestic side without proper isolation can damage the exchanger and contaminate the plumbing, so this is usually done by a technician.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
- A. O. Smith technical bulletin 45: thermal expansion (opens in a new tab)Background on pressure rise in a closed water system. Pressure testing and repairs are professional work.
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