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 2015 InspectApedia.com, All Rights Reserved.
Cast iron drain piping has been used in buildings for more than 100 years and can last for 50 years or longer. T
his 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 above left 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 above 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.
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
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.
Continue reading at CAST IRON DRAIN LEAK, ODOR, REPAIR or select a topic from the More Reading links shown below.
Suggested citation for this web page
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
(Feb 27, 2012) Anonymous said:
which pipe is best between galvanized and pvc pipe for cool water supply
Anon, if you are connecting a plastic pipe to any metal, you don't need an intermediate diaelectric fitting. The plastic is basically non-conductive.
You only need to install special diaelectric fittings (or brass, for example) between dissimilar metals - so you wouldn't go directly from iron pipe to copper without using an intermediate fitting, either a special diaelectric fitting (those have built-in plastic insulation components) or a brass fitting.
(Nov 26, 2012) Richard Young said:
I have moisture on my slab floor around the sewer pipe where it comes out of the slab. The pipe is completely dry and shows no sign of water leaking down to the floor. anyone out there have an idea?
If the drain itself is dry then perhaps
No, the moisture definitely moves away from the pipe and the floor isn't wet, just slightly damp. Had the line tested and the water didn't back up in the pipe. But as soon as I started the shower again the dampness started to show up. Roto Rooter thought that the elbow under the concrete was probably corroded.
Water may be entering the floor around the shower drain, or from a bad trap, or even from another shower leak point, following the drain to the point of exit at the floor drain.
Inspect the shower drain carefully, removing it's grate if you can, so as to check too for leaks around the drain flange.
(Nov 28, 2012) Richard Young said:
It doesn't matter whether it's the shower on the first floor or the second floor. The drain pipe is dry on the outside all the way down into the basement as far as the concrete slab. The last part of the sewer pipe that shows above the slab is a flange and that is dry on the outside also. No water shows except as moisture on the surface of the slab.
Can green pvc be used for sewer replacement INSIDE a residence in Nassau County NY that is under the slab? And does it require a permit/inspection? Thanks
For Nassau County code questions, as the local code inspector has final authority, I'd give them a call and ask that directly.
(Dec 29, 2012) John Juniet said:
Are second floor cast iron drain pipes general secured to the building on their run up the inside wall, or are they supported by themselves and the metal ties/supports in the basement floor joists? I have a leak somewhere along the main cast iron drain pipe from my second floor and am considering replacing all with pvc, but am anxious about the prospect of ripping open all my walls if there are support clips down the length.
Jan 30, 2013) Pumpkin said:
Hum & vibration in house. Wondering if it could be from saddle that connects our old cast iron pipe to new plastic system that the City installed? Anyone know about this problem.
Such connectors can conduct building sounds or vibrations from one area to another unless sound-isolating fittings were used.
8/8/14 John said:
I have a gas pipe running across the concrete floor of the garage that has gone rusty where the concrete has broken up (small area approx 6"). British Gas have inspected the pipe & told me there is no leak & I could cover it with concrete. My question is could I use PVA & Mortar mix or would this combination react with the rusty pipe?
For a detailed reply to John's question please see GAS PIPING DEFECTS
Questions & answers or comments about cast iron drain pipes in buildings.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References