Let’s keep the momentum. Let’s rant some more about green stuff.
The old sewer clay tiles need replacing; that decision has been made. But what material should the new sewer be made of?
This decision is made for us, and the answer is given in the Chicago plumbing code. All concealed (i.e. buried) sanitary sewers within a building must be cast iron soil pipe (CISP).
Iron? For waste water? In soil? Wow – wait a minute. This doesn’t make sense! Isn’t iron subject to corrosion? It may rust from the inside and outside. We are using low flow and low flush systems, which reduces the dilution of any acid based liquids (such as urine) and increases the probability of corrosion within a cast iron sewer pipe.
We will use a high efficiency condensing boiler. The condensate from such a boiler is known to be corrosive and further increases the probability of corrosion within a CISP. What about the longevity of this thing? Once I am done replacing it, I never want to touch it again, even if I get to be a 100 years old!
CISP Institute information proceeds to inform me that cast iron pipe are highly durable and probably the best material to use. Well, this is sort of expected. But I still have a hard time believing that CISP is as corrosion resistant as HDPE (high density polyethylene) or PVC (polyvinyl chloride) piping. Resistance of HDPE pipes is rated from pH 1.5 to pH 14, according to a sales representative. So maybe I need to take this with a grain of salt too!
Because HDPE or PVC pipes have good corrosion resistance, they also maintain good flow and slide characteristics, which in turn reduce maintenance or blockage compared to CISP’s.
And there is the carbon footprint issue. Wouldn’t you expect cast iron to have a much larger carbon footprint compared to HDPE or PVC? Time to find out.
The International Centre for the Environment (ICE) at the University of Bath (England) has published the ‘Inventory of Carbon & Energy’ for various building materials. I found data for all three materials (cast HDPE, PVC and iron) and was able to calculate the following carbon footprint per linear foot of a 4 inch sewer:
Even though the cast iron sewer has the biggest carbon footprint, the CISP Institute points to the recycled content of the product and labels it green (see page 131 of the CISP and Fittings Handbook).
PVC is a distant second, but is no angel. The production of polyvinyl chloride has all sorts of environmental issues associated with it. PVC piping (such as Schedule 40) is very popular though because of its low cost and ease of installation.
HDPE appears to have the lowest carbon footprint out of the three materials. It seems to have a better reputation than PVC with regard to environmental issues and is recyclable. It is more difficult to install compared to PVC and requires fusion or welding equipment for moist pipe joints.
Thinking this all through, and assuming that I have my facts straight, I really would like to use HDPE piping for the sewer replacement.
Tags: carbon footprint, energy, recycling, utilities
HDPE and PVC both release toxins into water, there is a plethora of information on PVC and Princeton University has done a study on HDPE and has found similar issues with the release of VOCs. Most may consider these quantities negligible but with the increases in usage these levels will reach a critical point sometime in the future, lest we forget the asbestos industry. Both PVC and HDPE degrade over time and it’s a lot quicker than people think. These products lose their elasticity and impact strength rather quickly compared to other products; ask anyone who does underground utility work. We tend to look at the industry that spawned these products for expertise or even the people that promote and use these products but this is rarely where you will find an honest answer. Certain products are preferred by the contractor simply because it’s cheaper, a little easier to handle, certainly easier to cut corners with and won’t last nearly as long–all good reason for a contractor to support such products. It provides them with a never ending supply of work. Some of the products that have been around for hundreds of years, are still around for good reason–they still work. We are still in a transitional state as it relates to new vs. old products, the old ones have a proven track record and volumes of data based on actual usage the new ones, well most of what’s published is based on marketing strategies and manufacturers hype. Studies independent of the industry is really the only way to determine what is good for the future and things that come from nature and can be returned to nature to me represent the best products, plastics are not natural.
Will the CISP be quieter? we have ABS black pipe in our house. You can hear the water cascading down the pipes when you are in the basement. It sounds like Archie Bunkers house.
Can you use HDPE pipe for the stack and CISP for the in ground portion? That would limit how much CISP pipe you need.
Roger, very good point. A CISP stack would be “quite” - we would have a hard time hearing the water cascading down the pipe.
The City of Chicago now allows PVC pipe for all DWV plumbing as long as it is not concealed (i.e. under ground). So I have to use CISP under the basement slab, but can use PVC for the stack etc. We were planning to encase the new PVC stack in two inches of spray foam (which we use already for the insulation). That should help with the vibrations and greatly reduce the noise transmission.
Hello, I was under the impression that in Chicago, they only allowed for pvc in residential use, 3 stories or less, and that copper, galvanized, and cast iron had to be used above grade and only cast iron below grade for non-residential use.
I just came across the above post stating that pvc can now be used for ALL drain above and below grade, but cast iron still must be used under ground. Hopefully a licensed plumber can confirm this? Is this a recent code change(when?) and does it in fact apply to commercial properties?
The plumbing union has had strong clout in Chicago and has been against pvc vs other cities, mostly due to the ease of use, less cost, and loss of business, so I am surprised if this is true. I was about to pay a very steep price to replace a very long run of drain cast iron pipes that run above basement ground, so I am praying this is true!
Thanks!!!
Mr Mike, I strongly recommend that you check with your design professional or the Department of Building what the plumbing code requirements are for your project.
The project described in the blog is a residential project. As such I had to use CISP in all concealed (underground) areas, but can use PVC above ground for the Drain, Waste, Vent (DWV) piping. Hot and cold water will require copper as far as I know. I have no knowledge of the commercial code requirements.
And yes, the Chicago plumbing union is resisting the modernization of the code. But there is also an issue in many cases with the States Health Department, which prevents the use of more sustainable plumbing technologies. If the State has not signed of or approved some of the more environmental technologies, the City cannot approve them either.