The history and problems of cast iron sewers pipes.

If your home is equipped with cast iron sewage pipes you will no doubt have comments in your inspection report regarding its presence and possibly issues.  So what are these issues and why the comments about them?

[tab: A Brief History]

Cast iron pipes have been manufactured and used in the United States since the early 1800’s.  The first usage was for water distribution but eventually also expanded to waste water disposal (soil pipes also called sewage pipes).  By the 1890’s an actual cast iron soil pipe industry took shape and was recognized.  Cast iron waste water piping was not the only product used over the years but it did provide a highly reliable and durable pipe that lasted much longer periods than other materials.

It wasn’t until the late 1960’s/early 1970’s that plastic PVC sewer pipe was introduced.  Once introduced the PVC pipe quickly became the choice for sewage pipe on new home construction.  PVC provided much easier installations, cheaper materials, and easier production.  Cast iron waste water piping was still being installed during the early PVC years and can be found in early 1970’s homes.  Cast iron waste piping is still used in many commercial, industrial and municipal applications, and even in some residential structures.

Older cast iron pipe in good shape

This is an example of older cast iron pipe in good shape.

A good quality cast iron pipe, installed under ideal conditions, has a life expectancy of 75 – 100 years, and possibly even more.  Cast iron does rust but when it does the rust actually forms a barrier layer over the remainder of the pipe which helps protect it from further rusting.  Since most cast iron pipes were thick walled to begin with even with some rusting inside they can handle the lower pressures of waste water disposal quite well and last a long time.  Cast iron also provides many other benefits in home waste systems that still makes it a good choice for homes.  However it is more expensive to purchase and install.  Also many plumbers of residential structures do not have the experience it takes to properly install and maintain it.  As a result PVC has taken over for the majority of home installations today.

 

[tab: The Issues]

For all of its good points cast iron does have some problems related to it.  One of the problems had to do with the varying quality of the pipe that was manufactured in earlier years.  Standards for cast iron pipe have been around since the 1800’s but like anything else they are voluntary standards.  It goes without saying when you have many companies competing for business there will always be one or more that choose to make an inferior product just to beat their competitions’ cost.  Unfortunately the quality of manufacturing issue happened more times than desired which has led to less than acceptable or defective pipe brands.

Older cast iron pipe in bad shape

An example of older cast iron in bad shape.

In this example picture this might have been a low quality cast iron pipe.  This pipe was only in the 40 year age range but already deteriorating badly.  The two darker rust spots were actually where the pipe was almost rusted through and waste water was seeping out.  It is unknown how much longer this pipe would last before completely rusting open and dumping waste on the ground.  The gnawing question on this pipe is that if it has rusted this badly above ground then what is its condition beneath the ground?

Cast iron pipes have always been more labor intensive to install and maintain.  They also require older methods that although they are taught in trade schools these methods are specific to cast iron.  For plumbers that do not install much, if any, cast iron they just do not have the experience needed to properly perform the installation.  When these inexperienced plumbers do attempt to handle/install the cast iron they add to the problems of cast iron pipes.

Cast iron pipe is highly resistant to the elements under proper conditions meaning they will not rust much or shift and break.  The majority of our original soils are naturally non acidic in nature or pose the conditions needed to accelerate damage to cast iron.  Unfortunately we have managed to change our soil’s contents over time through dumping, heavy use of chemicals around the home (inside and out), as well as other actions.  Then there are all of the chemicals we dump down our sinks and drains that work to deteriorate the cast iron from inside the pipe itself.

There are other causes of damage to cast iron that can reduce its life span.  For example our significantly shifting soils causing joint breaks and other damage, when foundations experience movement it to can shift and break these pipes, tree root damage, digging and other manual actions, etc.  All of this adds to accelerating the deterioration of even a high quality cast iron pipe.  When you start adding together the defects and other damaging factors of cast iron pipe you can see that even a high quality cast iron can potentially not survive its expected lifespan.

[tab: The Inspection Report]

In your inspection report you will no doubt read disclaimers regarding the condition of cast iron pipes.  Obviously when cast iron waste pipes are installed they are buried under the ground, in foundations, etc., mostly in concealed locations.  There is no way during a normal home inspection for an Inspector to tell you what the condition of these pipes are in these concealed locations.  The only way to obtain an idea of these pipes’ condition is using sewer scopes to actually look inside and down the length of these pipes.  However even a plumber can only view the interior of the pipe and can not see the exterior conditions without excavating them.

Cast iron pipes are not a problem piping system, and can be an exceptional system to have in your home.  But if the signs of issues are there it is well worth taking the next step of performing sewer scoping.  Listen to the recommendations of your Inspector and if you are uncomfortable then have sewer scoping performed anyhow.  This is a large purchase and you will be living in your home for quite some time so isn’t it worth being sure?

[tab: Links and References]

History of the sanitary sewage system

History of cast iron soil pipes

Ductile Iron Pipe Research Association

Cast Iron Soil Pipe Institute

 

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