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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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If you don't know what kind of heat your building uses, we explain how to figure out the answer at HEATING SYSTEM TYPES. If your heating system is not working properly, see NO HEAT - BOILER or NO HEAT - FURNACE.
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.
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. 
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.
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 a HARTFORD LOOP.
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 BLEVE EXPLOSIONS
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:
More details about steam condensate return pumps for residential properties are in process, photo contributions needed. CONTACT us.
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Technical Reviewers & References
For details about the controls, components and switches commonly found on hot water heating systems see the articles listed below in which we explain how to identify, set, re-set, repair, replace, or avoid problems with the components of a hot water heating system..