How to De-lime a Steam Boiler

Preventive maintenance will save you money in the long run.

Steam boilers, used in houses and buildings to generate steam to provide heat to radiators, build up lime and other contaminants over time, which must be removed for efficiency. Cleaning your steam boiler will enable it to heat your building more efficiently, using less energy to generate more heat. De-liming your steam boiler is a simple matter of adding a cleaner. This procedure will also extend the life of your boiler, saving you money in the short and long term.

Things You'll Need

• Bucket or tube for drainage
• Adjustable wrench
• Trisodium phosphate (or other de-liming compound)
• Flashlight
• Coat hanger
• Teflon tape

Instructions

1. Shut off the cold water supply line and hot water outlet line by closing the inlet valve and hot water outlet valve. Shut off the electric supply to the boiler at the breaker panel to avoid any possibility of electric shock.

2. Drain the boiler tank by opening the drain valve that is generally attached to the boiler body itself. Ensure that either a bucket or tube is present to funnel the water to a floor drain.

3. Remove the drain valve from the body of the boiler using an adjustable wrench. With the help of a flashlight, look inside the drain valve hole for lime deposits. These will look like white powdery buildup on the surfaces inside the boiler, usually at the base where water sits.

4. Scrape any large or obvious lime buildup off of the inside surfaces of the heater using a straightened coat hanger. Flush the system periodically by opening the cold water inlet valve and allowing the water to drain directly out of the open drain valve hole.

5. Replace the drain valve by coating the threads with a layer of Teflon tape and screwing it back into the body of the boiler tightly, using an adjustable wrench.

6. Loosen and remove the inlet water valve. Do this from the outlet side of the valve and not the supply side. Pour trisodium phosphate or another de-liming compound into the inlet tube, with the quantity depending on the manufacturer's recommendations. Allow it to sit in the boiler for about 15 minutes. Open the drain valve and drain the compound from the boiler.

7. Reattach the cold water inlet tube to the inlet valve by coating the threads with a layer of Teflon tape and tightening with an adjustable wrench. Flush the system out by opening the cold water inlet and leaving the drain valve open. Allow water to flow for about three minutes to ensure all de-liming compound has drained from the system. Close the drain valve and open the hot water outlet valve. Turn the power back on at the breaker and enjoy a cleaned and more efficient boiler.

Tips & Warnings

• Ensure that the electricity is shut off before performing maintenance on a boiler.

References

• Fix It Club: Steam Boiler Repair
• GE: Chemical Cleaning of Steam Generator Systems