Plumbing Alternatives: Plastic versus Cast Iron

At the outset it is easy to determine that plastic plumbing is a new concept which has caught the home owners attention in the last thirty years or so. In fact, any house built before the 1970s would have had cast iron pipes and plumbing as standard fitment. Another common metal used in pipes is copper, but its success is marred by its lack of resistance to corrosive water. Galvanized iron, on the other hand, has been found to clog too often, resulting in expensive cleaning jobs.

So that leaves us with just two options plastic and cast iron.

The point here is that a house should have reliable plumbing that does not leak, rust, blister and break, as any one of these can have disastrous and expensive consequences. Some of the problems home owners face is higher water bills because of water escaping into the ground, settling of the foundation due to underground leaks, and pinhole leaks within walls and ceilings that render them damp and moldy.

History has seen the use of cast iron as the typical metal for plumbing. The architects who designed the Fountains of Versailles in the 1600s used cast iron, and the fact that they are still functional speaks of their reliability and dependability. Cast iron was a difficult material to work with because of the weight involved and the tedious process of joining the parts. Installation took time, and a plumber had to join and seal pipes using a mixture of oil and hemp and molten lead. Times have changed, and today fixing a cast iron pipe is as simple as joining a plastic one. All it requires is a rubber gasket around which a stainless steel clamp is affixed, making the joint leak and weather proof. The other issue with cast iron pipes of the past is that they were sand casted, which left the walls of the pipe uneven in thickness, leading to leaks and cracks. Todays pipes are spun cast, leaving hardly any scope for issues with sidewall thickness. The only problem with cast iron plumbing involves cutting the metal to correct lengths but this too can be easily done using a cast iron snapper.

Apart from the long lasting nature of cast iron plumbing, it is also silent due to its higher density. These pipes can be more expensive than plastic pipes but in terms of longevity they would surpass the initial investment.

The plastic pipes available in the market are made of post-chlorinated polyvinyl chloride or simply CPVC. They are durable, cheap to buy, easy to install (with a little bit of primer and glue) and long lasting. They are not affected by corrosive or hard water, do not develop cracks and, most importantly, do not rust. If fitted well they will last a lifetime. The only problem with CPVC pipes is that they produce a lot of noise due to the low density plastic used. Water running down from the first floor of a house may very well be heard in the living room as it makes its way to the basement or the septic tank. The only solution to this problem is wrapping all the CPVC pipes with a good insulating material such as fiberglass. As designs and technology change, CPVC pipes are becoming quieter everyday, though. It is advisable to choose pipes with higher thermoplastic properties that not only reduce condensation outside the pipes (which can damage walls) but also curtail water flow noise.

So, which is a better option plastic or cast iron? Both products have their advantages and disadvantages, though cast iron is more environmentally friendly than plastic as it’s made from scrap, iron and steel, while CPVC is produced using crude oil. An intelligent option would be to use them together as they are completely compliant, using just a few adapters. Ideally, all underground piping, air vents, and fixture vents can be CPVC, while the vertical stacking of indoor pipes should be cast iron. This method will guarantee a quiet and durable plumbing system in any home.