Why do my radiators work, but I have no hot water? Warm radiators and cold faucets narrow the problem to one thing: how your boiler makes domestic hot water. A bad aquastat control, a failed circulator pump, or a faulty mixing valve will each stop that heat transfer. Meanwhile the same boiler keeps heating your radiators.
Few things jar like waking up in a warm apartment and stepping into a freezing shower. When your boiler is heating radiators but no hot water issue arises, it is incredibly frustrating. You know the boiler is working—the house is warm! So where is the hot water?
Start by understanding how your system separates home heating from water heating. That answers most of this common winter complaint.
How Your Boiler Heats Your Tap Water
In many older Brooklyn homes and brownstones, the boiler pulls double duty. Most local systems skip the standalone water heater. Instead, the boiler’s own heat warms your domestic water. This usually happens in one of two ways:
- Tankless Coils: A copper coil sits directly inside the boiler. Cold city water runs through the coil, picks up heat from the boiler water, then travels to your shower.
- Indirect Water Heaters: The boiler pumps hot water into a heat exchanger located inside a separate storage tank. This heats the domestic water stored in the tank without the two fluids ever mixing.
A warm house with a cold shower means the boiler still fires. The mechanism moving that heat into your domestic water has failed.
Common Causes for Hot Water Failure
- Bad Aquastat Control: The aquastat is the thermostat for your boiler’s water temperature. On an indirect water heater, a bad Aquastat never signals the boiler to fire when tank temperature drops. You get a full tank of cold water.
- Failed Circulator Pump: A dedicated circulator pump pushes boiler water into the tank’s heat exchanger. When that pump dies or sticks, the heat stays in the boiler.
- Faulty Mixing Valve: Tankless coils run dangerously hot, so a mixing valve blends the output with cold water before it reaches your tap. Mineral scale clogs that valve, and the line floods with cold water.
Trust Brooklyn’s Local, Family-Run Experts
These are not DIY fixes. This work takes high-voltage electrical testing and a working knowledge of boiler hydraulics. You need a trusted local professional who can restore your hot water quickly and safely.
At Stanley Lewis Plumbing & Heating, we have run heating work since 1973, now second generation. Since 1973, Stanley Lewis Plumbing & Heating is New York City’s premier plumbing & heating company. We specialize in the installation, service, and repair of gas-fired boilers and water heaters.
Our technicians arrive with trucks stocked for common plumbing and heating repairs: pipe, parts, and equipment. Stop shivering in the shower. Call Stanley Lewis Plumbing & Heating at 347-349-4851 today to get your hot water flowing again.