6 easy fixes for common steam-heat system issues

July 27, 2015

Plenty of steam-heat problems can be fixed, by you, with tools you already have. So if your boiler's making some noise, these are some ways you could safely fix it.

6 easy fixes for common steam-heat system issues

First, some steam-heat basics

  • Steam radiators get very hot, so be careful of what you put on them and how you touch them.
  • Most steam heat systems have one-pipe radiators. Steam enters a radiator, condenses to water as it gives off heat, then drains out the same pipe.
  • The less-common two-pipe radiators have both inlet and return pipes, like hot-water radiators.

1. Quiet knocking radiators

  • On a one-pipe radiator, knocking happens when a buildup of returning water blocks incoming steam.
  • To prevent knocking, make sure the inlet valve is completely open (or closed) and that the radiator is level or, if necessary, tilted toward the inlet valve.
  • Then, place a carpenter's level on top of the radiator. If there are height-adjusting bolts under the radiator's legs, use a wrench to screw them out. Or put shims (wedges of wood) under the legs opposite the inlet valve.
  • This should stop the knocking.

2. Adjust the heat

  • For a one-pipe radiator to work properly, the inlet valve must be all the way on or off.
  • The only way to adjust heat on an individual radiator is to install an adjustable air-vent valve.
  • On a two-pipe radiator, opening or closing the inlet valve controls its heat.

3. Check the boiler water level

If the water level in a boiler sinks too low, the boiler can burn out. Unless your boiler has an automatic water feed, check the glass gauge that shows the boiler's water level every 10 days during heating season, and more often in bitter weather. If the level is low, open the fill valve until the level is correct.

4. Flush sediment from the boiler

  • About once a month during the heating season, you need to flush the boiler to drain off a small amount of water to keep the sediment from building up.
  • To do this, turn down the thermostat so that the burners are off. Put a bucket under the cutoff valve, then open the valve and let the water run until it's clear.
  • Be careful: the water is hot.
  • Close the valve and open the supply valve to refill the boiler until the glass gauge is one-half to two-thirds full.

5. Check the pressure

  • To operate safely with the pressure that builds up, a steam boiler has a pressure control.
  • Check the pressure gauge just after the boiler switches off.
  • If it's far above the pressure setting, have the control replaced immediately.
  • Boilers also have a pressure safety valve designed to open before an unsafe pressure level is reached. To check if it's working, look at it while the boiler is running.
  • Pull its lever very briefly, then let go. A little steam should escape while the lever is up and should stop completely when you let go.
  • If the valve sticks or doesn't emit steam, have it replaced.

6. Install a better air-valve vent

  • To control the heat on a one-pipe steam radiator, install an adjustable air vent valve.
  • With the heat off and the radiator cool, remove the air vent valve with an adjustable wrench or a pipe wrench.
  • Take the air vent valve to a plumbing or heating supplier and buy a compatible valve and plumbing joint compound for use on steam radiators.
  • To install the new vent, apply joint compound to the threads, screw it into place and tighten it with a wrench.
  • To adjust settings, most vents have a screwdriver slot.

Some stea-heat problems can be fixed quickly and easily by you, if you know what to look for and do so with caution. With these simple instructions, getting your steam-heat system in perfect working order may have just become a little easier, and a little less expensive.

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