What an indirect water heater is
An indirect water heater is an insulated storage tank with no burner or elements of its own. Inside it is a coil. When the tank calls for heat, hot water from the boiler is pumped through that coil, and heat passes into the household water around it. The boiler water and the water you use never mix.
They are common in Connecticut homes heated by oil or gas boilers, especially where a household outgrew an old tankless coil or where the boiler was replaced and the installer added an indirect at the same time. In the rural east and the Litchfield Hills, many are paired with oil-fired boilers; in the cities and inner suburbs, more often with gas.
You can usually spot one by the two extra pipes running between the boiler and the side of the tank, and by the absence of a flue or burner on the tank itself. Our home page has a short guide to telling your hot water setup apart.
The parts that make it work
- The tank and its internal coil, where the heat exchange happens
- A control or sensor on the tank that decides when it needs heat
- A circulator pump or zone valve that sends boiler water to the coil when called
- The boiler controls, which often serve the hot water first when the heating and the tank call at once
- The usual water heater parts: relief valve, drain valve, shutoffs, and often an expansion tank and a mixing valve
A fault anywhere in that chain shows up as a hot water problem, which is why a good diagnosis follows the chain rather than guessing.
Common problems
Water not hot enough, or no hot water
Often a tank control or sensor that is not calling for heat, a circulator or zone valve that is not opening, or a mixing valve that has stuck. If the heating is also off, the boiler is the more likely common cause.
Running out sooner than it used to
Scale or sediment inside the tank, a coil that is not transferring heat well, a control set or failing low, or a household that has grown. In well homes, scale on the coil is a frequent contributor.
Heating goes cold when someone showers
Where the controls serve the hot water first, the boiler looks after the tank before the radiators. A long recovery time can make the heating pause noticeably, which can point to a tank or control issue on the hot water side.
Water around the tank
Leaks from fittings, the drain valve or the relief valve are repairable. A leak from the tank shell means replacement. Water between the tank and the boiler could be from either, and the technician will trace it.
Relief valve dripping
Often a sign that heated water has nowhere to expand, particularly on well systems. An expansion tank may be needed, or the valve may be worn.
On a private well?
Indirect tanks and well water
An indirect tank collects sediment like any storage tank, and minerals can scale the coil inside it over time, cutting how much heat reaches your water. Mention the well when you call so the technician checks the tank bottom and considers the coil's condition, not just the controls.
Say so and the technician will check for scale and sediment too.
The water heater side, and the boiler side
The local installers work on the indirect tank and its hot water connections, the controls and sensor that call for hot water, the circulator or zone valve serving the tank, and the valves and expansion tank on the household water side. Repairs to the boiler itself, its burner, and the heating system are outside this service. When the fault turns out to be in the boiler, the technician will tell you so plainly.
What to leave alone
- Boiler controls, burner resets and any oil or gas connection
- Wiring to the circulator, zone valve or tank control
- The relief valves on the tank and the boiler
- The mixing valve setting
Do note whether the heating is working normally, whether the problem started suddenly, and whether the boiler runs when you draw hot water. Those details speed things up.
How the service visit works
The technician confirms whether the boiler is running and heating normally, then follows the hot water chain: does the tank call for heat, does the circulator or zone valve respond, does hot boiler water reach the coil, and does the tank water warm as it should. They check the tank for leaks, sediment and the state of its valves, and on well homes, for signs of scale. They explain the fault and give you the price before any repair.
You get the price before any repair is made.
What affects the cost of indirect water heater service
- Whether the fault is a control, sensor, pump or valve, or the tank itself
- Parts availability for the tank and control brands involved
- Access around a tank squeezed in beside a boiler
- Whether flushing or an expansion tank is added at the same visit
- Emergency hours versus a scheduled call
How long indirect water heater service takes in Connecticut
Most indirect faults are traced within the visit. Control, sensor and valve repairs are often completed the same day if parts are on hand. A failed tank means a replacement, which is planned around access and around keeping the boiler connections tidy. Once repaired, the tank heats quickly when the boiler is running normally.
Indirect water heater questions
How do I know if I have an indirect water heater?
Look for a tank beside the boiler with no burner, flue or electrical elements of its own, and two pipes running between the tank and the boiler. The rating plate usually describes it as an indirect water heater.
Why is my indirect tank not heating but the radiators are hot?
The boiler is working, so the problem is likely in the hot water side: the tank control or sensor, the circulator or zone valve serving the tank, or the tank's own coil. A technician can trace it without touching the boiler's heating function.
Our indirect runs out faster than it used to. Why?
Sediment or scale, especially on a well, a control that has drifted, or a household that has grown. The technician will check each. If the tank is simply too small for how the household now uses hot water, they can talk through options.
Do you repair the boiler too?
No. We arrange work on the indirect tank and the hot water side only. If the boiler is at fault, the technician will explain what they found so you can call a heating contractor.
Why does my heating stop when someone takes a long shower?
Many systems are set up so the boiler heats the tank before the radiators. A little pause is normal; a long one can point to a tank that is slow to recover, a scaled coil, or a control issue on the hot water side.
Does an indirect tank need maintenance?
Like any storage tank, it benefits from periodic checks of its valves and, in well homes, occasional flushing. Some indirect tanks have anode rods and some do not, depending on the tank's construction. The technician can tell you what applies to yours.
Can an indirect tank be replaced without replacing the boiler?
Yes. If the boiler is sound and staying in service, a failed indirect tank can be replaced on its own. If the boiler is near the end of its working life, it is worth thinking about the hot water and the heating together.
Water is dripping from the pipe on the side of the tank. What is that?
That is the temperature and pressure relief valve discharge. Never cap or plug it. On well systems it often means heated water has nowhere to expand. Call and have the cause found.