 Cast Iron Drain Piping
Identification, Diagnosis, Repair
- Cast iron drain pipes in buildings
- Diagnosing & repairing cast iron drain connection & leak problems
- Diagnosing sewer gas odors traced to cast iron drain deterioration
- Types of leaks occurring in cast iron drain piping
- Life expectancy of cast iron drain piping
- Questions & Answers about cast iron drain pipes in buildings
- References
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Cast iron plumbing drain piping: this article lists our in-depth articles on inspecting, testing, and repairing problems with cast iron building plumbing drain waste vent piping, piping materials, clogged or noisy pipes, and types of pipe hazards or product defects. The articles at this website will answer most questions about water supply & drain piping of all materials and types.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Cast Iron Building Drain Piping: Identification, Diagnosis, Repair
 Other types of building piping systems are discussed at GAS PIPING, VALVES, CONTROLS and at OIL TANK PIPING DEFECTS. New York State License # 16000005303 (inception to 2008).
Cast iron drain piping has been used in buildings for more than 100 years and can last for 50 years or longer. This heavy material is available in diameters from 2" and up, with typical main building drains of 4" to 6" in diameter in residential buildings. A hub system connects pipe sections, originally using melted lead to seal the joint against wastewater leaks or sewer gas odor leaks.
The cast iron pipe hub and stub were wiped with oil to remove water, avoiding a dangerous steam flash when lead was poured into the fitting. Most modern cast iron connections are made using rubber or plastic fittings that no longer require heating and melting lead.
The illustrations (left) show accessing a cast iron drain cleanout and two methods of emergency, temporary repair of leaks in drain piping. |
Making New Drain Connections to Old Cast Iron Drain Piping
Our photograph of cast iron drain piping (below left) demonstrates two methods by which connections have been made to newer copper drain lines. At upper left a black plastic hub fitting has been used to connect the 4" copper drain to the cast iron drain line.
At center-right in the left-hand photo a questionable clamp-on type fitting has been used for the same purpose, including a makeshift clamp using a block of wood to accommodate use of the wrong-sized clamp around the cast iron drain. Stains on the upper section of piping indicate that this drain system has been leaking.
Our photograph at below-right shows three clamp-on connectors joining cast iron and plastic drains to the cast iron sewer line.
Cast Iron Drain Piping Leak & Odor Locations, Causes, Diagnosis
Our photograph (below left) shows an odd double-hub connection on a vertical section of cast iron drain piping in a 1935-built home in poughkeepsie, NY. You can see by the rust stains that this cast iron pipe joint has been leaking for some time, that the concrete "repair" action was not fully effective, and that the basement is exposed to unsanitary conditions due to sewage leakage.
Our second cast iron drain leak photograph (below right) shows a different type of drain pipe leak: sewer gases. This fitting and collection of galvanized iron elbows and nipples should be removed and the opening in the vertical cast iron drain plugged to stop potentially dangerous sewer gases from entering the building. We suspect that this drain was once used to receive water from a basement dehumidifier or water softener, but it is no longer in use. The dry "trap" formed at the bottom of the piping "U" no longer serves to keep sewer gases out of the building.
Watch out: sewer gases may be both unsanitary and also risk of a very serious methane gas explosion. See SEWER GAS ODORS.
Several types of leaks occur in Cast Iron Piping:
- Improper cast iron pipe connections or retrofit connections (see our photo just below), including poorly-prepared lead hub joints as well as use of improper clamp on or hubless connectors
- Perforations from defective cast iron material or corrosive conditions
- Splits in cast iron drains due to freezing - occurring when the drain line is blocked or improperly pitched, left full of wastewater, and exposed to freezing conditions
- Improper support leading to movement and separation of pipe joints.
- Breaks at cast iron pipes or pipe joints due to mechanical impact, movement due to poor support of the cast iron piping, or similar causes.
Our photograph shows that the rope trying to secure the galvanized drain line to the cast iron sewer piping confirm a history of leak troubles and improper plumbing connections. |
Cast Iron Drain Pipe Leak & Repair Case - Odors Lead to Discovery of Under-Floor Drain Leaks
Cast Iron Drains Receiving Roof Gutter Drainage May Burst Basement Floor Slabs
Often on city lots that are flat and poorly drained, builders or building owners were pressed to decide how to get rid of rainwater spilling off of building roofs and through the gutter and downspout system.
The best approach is to route these drains to a nearby city storm drain, pumping if necessary but best by gravity. This avoids overloading the city sewer system during periods of heavy rainfall. Our photograph (left) shows a New York City storm drain overflow station (officially, a: New York State Wet Weather Discharge Point) where excess drainage is dumped into the Hudson River when more water or wastewater enters the city sewer system than can be handled. The green sign atop this drain warns
If you see a discharge during dry weather, please call 311 - DEP (Department of Environmental Protection).
Overloading a city's sewer often means that raw sewage is simply overflowed or dumped into local rivers or streams.
But It was common in previous generations for builders to rout (usually cast iron) drain pipes from ground-level outside of a building into the building, under the basement floor slab, and out to the municipal sewer system. These drains were used to receive roof gutter drainage and dispose of it into the city sewers.
Our photo (left) shows an in-basement cast iron drain line that originally received outside gutter/downspout drain water. At the time of our inspection that system had been changed and downspouts were routed to above-ground drains (unfortunately still too close to the building to assure a dry basement).
A problem with the in-building, under-floor piping disposal of roof runoff, besides overloading the city sewers in wet weather, is that eventually the under-floor drain may become clogged, perhaps with leaves washing into the drain from the building's gutters. The best result of that problem is that the drain stops draining and gutters spill outdoors along the foundation, perhaps leading to basement water entry, rot, mold, and insect damage.
Still more troubling, a blocked under-floor drain in a building left with no heat sometimes led to frozen drain pipes and burst, heaved piping and floor damage in the building, followed by an in-building flood when freezing weather changed to a thaw.
If you have roof gutters connected to drains that enter the building and are routed to the sewers, (a step still permitted and even required in a few communities), reconnecting the drains from outside ground-level to a nearby storm drain may be a better approach.
Tracking Down Leaky Cast Iron Drain Pipes Under a Floor Slab that Sent Sewer Gases into Transite (Asbestos Cement) HVAC Ducts
Details of this sewer gas odor case, cast iron drain leak, and repair are at CAST IRON DRAIN LEAK, ODOR, REPAIR. Excerpts are below.
A reader (Conrad) provided us with the photographs and case history of the successful track-down of sewer gas odors in a building (SEWER GAS ODORS). The case began with a complaint of sewer gas odors in the building's heating duct work system.
Details about the case illustrated just below, including more pictures and notes on how the building owner tracked the sewer smell to the basement floor slab (and transite heating ducts in the slab) can be read at CAST IRON DRAIN LEAK, ODOR, REPAIR.
SLAB DUCTWORK - catalogs the functional and environmental problems found when HVAC air ducts are routed in or below floor slabs.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
- John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
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Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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- Thanks to reader Conrad for discussing an under-slab sewer gas odor source traced to a combination of transite heating ducts in the floor slab and leaky cast iron drain piping - January 2010
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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