Advice for draining your hot-water heating system

It's important to know how to clean, maintain, and drain your hot-water heating system. These practices will keep your showers hot and your system running strong.

Advice for draining your hot-water heating system

Remove rust and sediment buildup

Over time, a boiler can become clogged with rust and other sediment. To check for this, follow these steps:

  • Turn off the burner and the water supply to the boiler and let the system cool. Then, open the drain valve and let water run into a bucket.
  • If you find sludge, your entire system needs to be drained. For best results, have a heating contractor power-flush the system using chemicals and hot water.To drain it yourself:
  • Turn off the burner and the water supply and let the system cool. Open the air vents on the radiators or convectors at the highest point of the system.
  • Connect a garden hose to the drain valve and run it to a drain. Open the valve and let the system drain.
  • When it has emptied, close the air vents and turn on the water supply. Let fresh water flush the system until it runs clean, then close the drain valve and refill the system.

You can also prevent sediment buildup by adding a rust-inhibiting compound (sold by heating supply stores) to the boiler. To do this, unscrew and take off the pressure gauge on top of the boiler and pour the compound in through the hole.

Drain your expansion tank

On older hot-water systems, the boiler usually has a large cylindrical expansion tank, which provides an air cushion that lets the hot water in the system safely expand. If water is dripping from the boiler's safety relief valve and the expansion tank feels hot all over, the tank is waterlogged and needs to be drained. Here's how to do it:

  • Turn off the system and let it cool. Close the shutoff valve between the boiler and the tank.
  • Connect a garden hose to the combination drain valve on the bottom of the tank, run the hose to a drain and open the valve.
  • After the tank has drained, close the combination valve and reopen the shutoff valve.
  • Bleed the radiators or convectors.

If the smaller, diaphragm-type expansion tank on a newer hot-water system becomes waterlogged, have it recharged (refilled with air) or replaced by your heating contractor.

Keep your system strong

With regular monitoring and maintenance, your hot-water heating system can run perfectly for years to come.

The material on this website is provided for entertainment, informational and educational purposes only and should never act as a substitute to the advice of an applicable professional. Use of this website is subject to our terms of use and privacy policy.
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