How to Drain a Radiator Boiler System
The boiler in a hot water heating system heats water and moves it through the home's radiators by way of a series of pipes. The boiler's efficiency is inhibited by sediment and rust that can build up in the system over time. Draining, then refilling the boiler once a year can extend the life of a water heating system substantially. Draining the boiler is not difficult, though the process can take several hours. Does this Spark an idea?
Things You'll Need
- Garden hose
- Screwdriver or valve key (available at hardware stores)
- Wrench
- Elbow fitting
- Funnel
- Rust inhibitor (available at stores that carry heating supply materials)
Instructions
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How to drain a radiator boiler system
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1
Turn off the boiler's power by shutting off the circuit at the main service panel. Allow the boiler to cool for at least two hours. Turn off the boiler's water supply.
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2
Attach a garden hose to the drain located at the bottom of the boiler. Put the hose's other end into a utility sink or floor drain. Open both the boiler drain valve and the bleed valve of the radiator at the highest location in the house. To open the radiator's bleed valve, use a screwdriver, a valve key, or, on some radiators, the provided knob. Water will begin to drain out of the boiler.
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3
Open the bleed valve of a radiator located closer to the boiler when water stops draining. Allow the water to drain until the flow again stops. Locate the valve or gauge at the top of the boiler and remove it with a wrench.
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4
Close the boiler drain valve. Place an elbow fitting into the open gauge or valve opening. Place a funnel into the elbow fitting and pour in rust inhibitor. Rust inhibitor can be purchased at stores that carry heating supply materials. Consult the instructions on the rust inhibitor container for how much to pour into the boiler.
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5
Remove the elbow fitting and the funnel and re-attach the gauge or valve. Close all of the open radiator bleed valves. You are now ready to refill the boiler.
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1
Tips & Warnings
Draining a boiler can be smelly work: it's best to do this job during the summertime, with the windows open.
Do not attempt to drain a boiler without first shutting off the boiler's power at the main service panel.
References
Resources
- Photo Credit highperformancehvac.com
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Comments
View all 6 Comments-
you can buy rust inhibitor at auto parts stores for car radiators.
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zymer
Feb 02, 2011
Sorry, earlier I was wrong. During draining you should first open ONLY the radiator bleed bleed valves at the upper level, and then wait before opening those at the next lower level; exactly as author Kerns advised in step-3. Otherwise the hydrostatic head still present above the lower radiators will cause dirty water to spurt out of them, possibly staining carpets. However, during refilling go ahead and open the bleed valves on all of the radiators. Then be prepared with 1-liter vessels at each radiator in order to catch the bleed water until you've reclosed the bleed valves. -
zymer
Feb 01, 2011
(cont. from previous comment) ... via its bottom drain fawcet and a garden hose discharging into a utility sink. But that will take a long time because the old simple expansion tanks are generally not equipped with vent valves. Conversely if you can easily move the hanging expansion tank and hear some water swishing about inside (indicating that it's mostly empty) then do NOT drain it because it's just the way it ought to be. And in that case, opening/closing the isolation valve in its supply pipe will have no effect on the system draining procedure.
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zymer
Feb 01, 2011
Like mdewar stated, may as well open ALL of the radiator vents when draining, as that does no harm, yet later they MUST all be open before you commence refilling the system; in order to avoid air entrapment. It can be hazardous draining very hot water, plus garden hoses are not rated for hot water. That's why the author Kerns instructed a cooled down boiler. It's helpful that mdewar mentioned the expansion tank, but normally it's not necessary to drain it unless somehow it's become almost completely filled with water. If it's a simple (non-diaphragm) tank that is decades old, then it's probably hanging with steel straps. Before draining it, try to lift the end of it that's opposite the piped end. If you can feel that it's very heavy then it should be drained... (to be cont.)
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zymer
Feb 01, 2011
Overall a good article. It's the only one that suggests the idea of adding a boiler water treatment (rust inhibitor). But just try to find such a product. Environmental regs have just about banned their sale in the USA. The valve to be removed for adding such a product (or any of the widely available stop-leak additives) that the author Kerns was referring to is the pressure relief valve located at/near the boiler top surface.
