Condensate return sysem on steam heat (C) D FriedmanSteam Heat Condensate Piping, Pumps, Return LInes

  • CONDENSATE RETURN PIPES, PUMPS, STEAM - CONTENTS: Condensate Return Pumps & Condensate Systems on Residential Steam Heating Systems - how to identify & troubleshoot steam condensate return piping. Sources of trouble in the Steam Condensate System; corrosion on Steam Piping & Corrosion Control by Chemical Treatment of Condensate or Water. Leaks in steam condensate return piping. Steam condensate reservoirs & steam condensate pumps, problems with.
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Steam heating system condensate pumps & piping: this article describes and illustrates steam condensate return piping, condensate return pumps and steam condensate return reservoirs. We also discuss leaks in steam condensate piping lines and chemical treatment of steam condensate.

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Guide to Condensate Return Pumps & Condensate Systems on Residential Steam Heating Systems

Steam condensate return pump system (C) D Friedman

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Our photo at left illustrates a steam condensate return pump system in a New York home.

Where condensate is unable to flow by gravity back to the steam boiler, a reservoir tank (under our client's hand at left) receives condensate from a low point in the building.

A float control and small pump moves condensate back to the steam boiler. In the condensate receiver system shown at left and on similar systems we have inspected in which the steam boiler is not even in the same building as the condensate receiving system, a control on the receiver sends water back to the boiler,

Watch out: where a separate condensate receiver is used, a feed pump to move condensate back to the boiler must be energized by a boiler-mounted condensate return pump controller. - Weil McLain 78

This steam system includes a plastic tank and injector pump used for chemical treatment of the steam condensate. When the float in the condensate return tank activates the condensate return pump, that same circuit activates the small chemical injector pump mounted on top of the plastic reservoir at the right in our photograph.

Some Sources of Trouble in the Steam Condensate System

Condensate return line leak (C) D FriedmanWatch out: problems such as blockages or leaks in steam condensate return systems can have various causes and can originate in many areas including at least these:

  • Improperly sloped or routed condensate return piping can prevent condensate from returning to the boiler or can create blockages in piping that prevent steam heat from serving some radiators or building areas.
  • A steam trap that is not working properly - see STEAM TRAPS
  • A wiring error or electrical failure that causes the condensate pump to run backwards
  • A system operating problem (such as bad steam vents) or other events (a leak) or conditions (water chemistry or poor maintenance) that causes too-frequent in-feed of water to the boiler, leading to corrosion and leaks in the condensate piping or in the boiler itself
  • Improperly set or damaged boiler water feeder or water level controls
  • Condensate reservoir leaks
  • Condensate pump motor troubles: motor not running, won't start, won't stop running, noisy
    • See ELECTRIC MOTOR DIAGNOSTIC GUIDE for condensate pump motor problems
    • Check for a dirty or clogged strainer blocking condensate flow in the reservoir or at the pump
    • If the pump wont' stop running check for a leaky failed steam trap (s) or a valve that has been left partly closed or is debris-clogged in the condensate discharge line; also check for a broken or debris-clogged pump impeller.
  • Dirt or debris blockages at steam traps, or anywhere in the condensate return system piping, including at the Hartford Loop

Corrosion on Steam Piping & Corrosion Control by Chemical Treatment of Condensate or Water

Steam condensate return pump system (C) D Friedman

Our second steam condensate return system (left) shows the reservoir and condensate pump motor (grey pump and new piping on the right side of the condensate reservoir at the left in that picture).

Steam condensate may be corrosive due to an improper pH level of the building water supply, or condensate water may be particularly corrosive to steam piping or to the boiler itself due to the formation of carbonic acid in the condensate liquid.

Carbonic acid itself forms because of the combination of high levels of carbon dioxide CO2 and oxygen in the steam piping system. Steam piping that is made of copper is also vulnerable to a combination of ammonia and oxygen in the steam condensate.

Chemical treatment of steam condensate is typically done to reduce corrosion in the steam piping.

Other chemical treatments of water in steam boilers may be performed at the boiler itself to adjust the pH of the water or to control levels of corrosive carbonic acid using neutralizing amines or to control oxygen levels. [1]

A second approach to controlling steam system corrosion used particularly in steam systems that use a high volume of make-up water is the use of filming inhibitors or filming amines.

In a third approach to controlling steam system corrosion, water entering steam boilers may also be "de-aerated" by a feed water heater that removes excess oxygen mechanically.

Where do corrosion and leaks most often appear in steam piping?

Corrosion in steam piping is most likely to appear in the sections of steam condensate piping that remain filled with condensate. Those piping sections are found near the steam boiler itself or at steam condensate return reservoirs and pumps.

To control or reduce the corrosion and leaks caused by corrosive steam condensate the steam boiler water may be pre-treated or the condensate may itself be treated as we illustrate in our photo above.

Leaks in Steam Condensate Return Piping

Steam condensate return leaks (C) D Friedman

Our photograph at left shows a leaky steam condensate return line close to the steam boiler.

This steam condensate line leak has been dripping for more than a decade. Unlike a hydronic heating boiler system, because the pressure in the steam condensate return line is low, the leak was not noticed by the homeowner and it was ignored by the heating service technician.

While not all of the piping is clearly visible in this image, you are also looking at part of

Because steam condensate may be quite corrosive in steam heating systems commercial systems and some residential steam heat systems use additives or water conditioners to minimize those effects. Without the Hartford Loop properly sized and piped at the condensate return to the boiler, complete loss of boiler water could follow a leak in the condensate line.

In turn, loss of boiler water can destroy the boiler or can lead to catastrophic

Our opinion was that the piping in this steam condensate line section all should be replaced, but it was reasonable to wait until the end of the heating season rather than having to shut down the heater during freezing-cold weather.

Watch out: never pick at corrosion on a heating pipe: we warned the homeowner not to poke or pick at the corrosion on this piping. Disturbing the condensate return pipe was likely to result in a sudden and much larger leak that could leak badly, resulting in basement water problems and increased steam boiler water consumption.

Watch out: a leak in the condensate piping of a steam heating system can lead to very expensive damage including:

  • Leaks into the building causing rot, inviting insect damage, or leading to a costly mold cleanup job
  • Excessive water in-feed to the boiler, leading to increased rate of corrosion in the condensate piping or even the boiler itself, risking the development of additional leaks that can destroy the boiler

More details about steam condensate return pumps for residential properties are in process, photo contributions needed. CONTACT us.


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