Short on hot water? Start here
Spot the pattern first
Sudden or gradual?
A change overnight suggests a failed part. A slow slide over months points to sediment, wear or a household that has outgrown the heater.
Worse in winter?
If it is fine in summer and short in January, cold inlet water is likely part of the story.
What makes the hot water?
A tank, a tankless unit, an indirect tank beside the boiler, or a coil inside the boiler each run out for different reasons.
How long before it fades?
Time a hot shower. A rough number helps the technician more than "not long".
Any smell of gas: leave the house and call the gas utility and emergency services from outside.
A carbon monoxide alarm: get everyone out and call emergency services from outside.
Why hot water runs out
Something has partly failed
On an electric tank, one of the two elements or thermostats may have failed, leaving the heater running on half its capacity. On a gas, propane or oil-fired tank, a burner that is not firing properly heats slowly. A broken dip tube lets incoming cold water mix at the top of the tank instead of the bottom, so hot water turns lukewarm quickly. These are usually repairable.
Sediment has taken up the space
In homes on a private well, sediment can build a thick layer on the tank bottom. It takes up room that should hold water and insulates the burner from the water above it. The result is less hot water and slower recovery. See sediment from a well.
The heater is too small for the household
More people, a new bathroom, a large soaking tub or a rainfall shower can outgrow a heater that was adequate when it went in. This is a sizing question rather than a fault.
The water coming in is colder
Every gallon has to be heated from whatever temperature it arrives at. In winter, and all year on many wells, that starting point is cold, so the same heater delivers less usable hot water and takes longer to catch up.
When the boiler makes the hot water
Many oil-heated Connecticut homes make hot water with a tankless coil inside the boiler. The coil heats water as it passes through, with no storage, so it can only deliver so much at once. Run two showers, or a shower and the dishwasher, and it falls behind. Mineral scale on the coil, which builds faster with some well water, makes it worse. A coil that used to cope and now does not may need cleaning or replacing; see tankless coil problems.
An indirect tank stores hot water heated by the boiler and usually handles demand better than a coil. If an indirect is running short, the cause may be its control or sensor, the pump or valve that sends boiler water to it, or a tank that is small for the household. See indirect water heater service.
Tankless units that run cold
A wall-hung tankless unit does not run out in the same way a tank does, but it can fail to keep up. The usual reason is flow: too many fixtures at once for the unit's size, particularly when the inlet water is very cold. Scale in the heat exchanger and some fault conditions can also reduce output. See tankless repair.
What to leave alone
It is tempting to turn the temperature up to make the hot water last. Leave the thermostat and gas control settings, and any mixing valve on the outlet, to the technician; they need to see the heater as it normally runs. Do not open electrical covers, touch burner parts, or drain the tank to clear sediment.
Sediment is a common reason well homes run short.
How it gets fixed
The technician first checks whether anything has failed: elements, thermostats, burner, dip tube, controls. They look at sediment levels and, on a boiler-fed system, check the coil or the indirect tank's controls. If a part has failed, the fix is a repair. If sediment is the cause, a flush may help, or the tank may be too far gone for flushing to make a difference. If nothing has failed and the heater simply cannot keep up, the options are sizing-related: a larger tank, an indirect in place of a coil, a second heater for a distant bathroom, or a different type of heater. Our sizing guide goes into how that is worked out.
You are given the price for whichever option you choose before any work begins.
Each option is priced so you can compare them.
What affects the cost
- A failed element, thermostat or dip tube is a modest repair
- Flushing is simpler than replacing, if the tank is still in good condition
- Coil cleaning, coil replacement and adding an indirect tank sit at very different points
- Replacing with a larger or different type of heater costs the most, and access affects it
How long it takes
Finding the cause is usually done in one visit. Simple part replacements often happen then and there. Changing the heater or adding an indirect tank is a planned job, usually scheduled once you have chosen the option.
Running out of hot water: questions
Why does my hot water run out faster in winter?
Because the water coming into the house is colder. The heater has to raise every gallon further, so it delivers less usable hot water and recovers more slowly. Well water in particular can be cold year-round. A heater that is only just big enough in summer can fall short in January.
Why does the hot water go lukewarm after a few minutes?
Common causes are a failed lower element or thermostat on an electric tank, a broken dip tube mixing cold water into the top of the tank, or heavy sediment. On a boiler with a tankless coil, it can simply be the coil reaching its limit.
Can I just turn the water heater up?
Leave the settings to the technician. Turning it up can mask the real problem. If a part has failed or the heater is undersized, turning it up is not a fix, and the technician can recommend a sensible setting once the cause is known.
Our boiler coil used to be fine. Why is it running out now?
Mineral scale builds up inside coils over time, especially with some well water, and reduces how much heat they can pass to the water. Household use may also have grown. A technician can check whether the coil needs cleaning, replacing, or whether an indirect tank would suit the house better.
Would an indirect tank fix running out of hot water?
Often it helps a great deal compared with a tankless coil, because it stores heated water rather than making it on demand. It depends on the boiler staying in service, though. If the boiler is due to be replaced or removed, it makes sense to plan the hot water alongside that decision.
Is a bigger tank the answer?
Sometimes, but not always. If a part has failed or sediment has taken up space, fixing that restores capacity without a new heater. If the household has genuinely outgrown the heater, a larger tank, a faster-recovering unit, or a second heater nearer the far bathroom are all options.
Does sediment really reduce how much hot water I get?
It can. Sediment occupies space at the bottom of the tank and slows heat transfer from the burner to the water. In well-water homes the layer can become substantial. Whether flushing will help depends on how long it has been building.
Our tankless unit goes cold when two showers run. Is it broken?
Not necessarily. Tankless units have a flow limit, and it drops when the incoming water is cold. Two showers in January can exceed it. Scale or a fault can also reduce output, so a technician can check the unit before you decide whether it is a repair or a sizing question.
What should I tell you when I call about running out of hot water?
What makes your hot water, the fuel, roughly how long a hot shower lasts, whether it is worse in winter, whether the change was sudden or gradual, how many people are in the house, and whether you are on a private well.