Water-Based Heating Systems
Instead of heating air, hot-water heating systems use a boiler for heating water and pipes through which hot water or steam flows to radiators or convectors in individual rooms. The most common maintenance task for radiators is to release the air that can become trapped inside the radiator. The radiator won't feel as hot as it should in this case, especially near the top. This is especially common after the system has been sitting unused during the nonheating season. Check all the radiators to determine how many are a problem.
To release the air, begin with the radiator nearest the boiler (with the heating system on). Look for the air vent, bleeder valve, or vent screw, usually located on the top of one side of the radiator unit. You can use a tool called a radiator key to open the vent, but a flat-bladed screwdriver may also work. Hold a small bucket under the air vent, open the vent, and hold it open until water begins to flow out of the vent. (Wear rubber gloves to protect your hands, because the water from the vent will be hot and may splash.) Then, close the vent quickly.
Repeat the process with the other radiators that you suspect have air trapped inside them. When you're checking your radiators, also make sure that the valves are sealing properly, as leaking valves can damage flooring. Keep your radiator surfaces clean and dust-free, and make sure that the heat radiating from them isn't blocked by furniture or other obstacles.
If you have convectors (with thin fins) instead of radiators, they may or may not have air vents. If not, call in a professional to bleed the system.
There are several maintenance tasks involved with steam systems. First, keep an eye on the system's water-level gauge. This should be located near the boiler, and it should have the required water level marked. If it doesn't, ask your service professional to mark it for you. If the water level is below the mark, open the water supply valve until the water reaches the required level.
If you've never opened the water supply or drain valves before, have a qualified service technician open them for the first time, because over time the valves can seize, and accumulated mineral deposits can block them when you try to close them. Once you know the valves are operating properly, start your own maintenance routine.
Steam-based systems often have noisy radiators. To eliminate knocking, first open the radiator's valve; then raise the opposite end of the radiator slightly, either with shims or by adjusting the bolts in the radiator legs. This should stop water inside the radiator from blocking the steam.
One of the problems with water-based systems is that water contains minerals that can leach out and be deposited on boiler interiors, reducing their lifespan. You may be able to prolong the lives of steam-based systems by opening the drain valve monthly. Place a bucket under the drain valve, and turn the valve so that water begins to drain. (Wear rubber gloves to protect you, as this water is hot.) Keep the valve open until the water looks clean.