Sewer Survey Says

With each passing year, many sanitary sewer systems across North America continue to work past their life-span. They are either in deteriorated condition and replaced or are being rehabbed into working condition using the latest technologies available to municipalities.

Trenchless Technology wanted to know what types of pipe are being used on the sewer systems today and what choices public works officials and engineers are making about what they are putting in the ground. Today, both pipe selection and installation methods have any number of options available to municipalities. There is a diversity of pipe materials available for any given project and that project may involve pipe bursting, sliplining, directional drilling or pipe jacking to name a few.

We wanted to get a glimpse into what cities are using as their conduit to transport their wastewater, as well as what trenchless methods they are using to install or rehab their existing pipe. In 2004, we conducted an informal survey of municipalities to gauge what their pipe selections were and what criteria was most important to them when making these decisions. We conducted the survey again in 2008 and have asked for more information in 2010. In all three endeavors, we informally surveyed sewer system operators and consulting engineers from North America. Below are the results of the 2012 non-scientific poll.

Sharon M. Bueno is managing editor of Trenchless Technology.

(Editor’s Note: For some questions, respondents were allowed to check more than one answer, making some of the percentages exceed 100 percent.)

1. How many miles of sanitary sewer are in your system?

We wanted to gauge how large a system our respondents dealt with and we got a wide range of answers from seven miles to 9,000 miles. Most respondents seem to fall into the 100- to 1,500-mile range.

2. Rate the importance of the following characteristics when choosing pipe material:

Just like our 2010 poll, the top two answers for this question were the longevity/design life and meeting standards, at 84 percent and 81 percent, respectively, finding it “extremely important.” Price and ease of installation had the least amount of “extremely important” responses at 42 percent and 39 percent, respectively; however 55 percent of respondents indicated that ease of installation was “important” and 53 percent selected price as important.

	Extremely Important	Important	Not important at all
Price	42%	53%	5%
Meeting standards	81%	16%	3%
Compatibility with existing system	53%	38%	8%
Ease of installation	39%	55%	5%
Longevity/design life	84%	13%	3%

3. What type of data do you use to evaluate your sewer pipe?

Here, the clear favorite method to evaluate their sewers was use of CCTV at 93 percent, with considering the pipe’s age coming in second at 75 percent

CCTV – 93%
Age – 75%
Overflow History – 62%
Stoppages – 46%
Laser Profiling – 10%
Sonar – 10%
Sewer Scanning – 7%

4. What type of pipe do you have in your sanitary sewer system?

The results of our 2012 and 2010 survey are identical here for the top two places with 90 percent saying PVC was the pipe most found in their systems, with clay selected by 88 percent of our respondents. Concrete came in third with 70 percent and HDPE was fourth at 56 percent; in our 2010 survey these swapped spots. In the “Other” category, wood and truss pipe was noted.

PVC – 90%
Clay – 88%
Concrete – 70%
HDPE – 56%
Iron – 48%
Asbestos Cement – 44%
Brick – 23%
Fiberglass – 18%
Steel – 18%
Polymer Concrete – 9%
Other – 12%

5. Most common problems with sewer pipe:

No surprise here that inflow and infiltration were the top response, at 80 percent. Broken/collapsed pipe was the second most selected problem, at 63 percent. Under Other, roots and corrosion were noted as problems with their sewer pipe.

Inflow/Infiltration – 80%
Broken/Collapsed pipe – 63%
Stoppages – 32%
Overflows – 29%
Other – 7%

6. How much of your system is composed of the various pipe types:

Just as in our 2010 survey, the top response to this question was PVC, at 94 percent, with clay a close second at 88 percent.

PVC – 94%
Clay – 88%
Concrete – 66%
Asbestos cement – 52%
Brick – 31%
HDPE -52%
Iron – 49%
Fiberglass – 20%
Steel – 20%
Polymer concrete – 16%

7. How old is the pipe in your system?

More than 100 years old – 44%
75 to 100 – 62%
50 to 75 – 80%
25 to 50 – 91%
0 to 24 – 81%

8. Have you changed your design life requirements in the last five years?

Yes 24%
No 76%

9. Do you only accept certain pipe materials?

Yes 81%
No 19%

10. If yes, which pipe materials are accepted?

The results here are similar to our 2010 and 2008 survey. With regards to underground infrastructure work, PVC was the top response at 93 percent, with HDPE following with 59 percent.

PVC – 93%
HDPE – 59%
Concrete – 32%
Iron – 30%
Clay – 16%
Fiberglass – 15%
Polymer Concrete – 11%
Steel – 8%
Other – 7%

11. What type of pipe is the easiest to maintain/rehab?

The results of this questions were similar to those in 2008 and 2010, with PVC selected the most by our respondents at 79 percent. HDPE finished second with 25 percent and concrete third with 15 percent.

PVC – 79%
HDPE – 25%
Concrete – 15%
Clay – 11%
Iron – 7%
Fiberglass – 4%
Polymer concrete – 2%
Steel – 2%
Brick – 1%
Other – 2%

12. What type of pipe is the most difficult to maintain/rehab?

A low number is what you want to see next your pipe for this question so HDPE, fiberglass, polymer concrete and PVC advocates will be happy. Taking the top spots with our respondents was clay at 50 percent and concrete at 29 percent — the same as our poll in 2010.

Clay – 50%
Concrete – 29%
Brick – 22%
Iron – 14%
Steel – 8%
HDPE – 3%
PVC – 3%
PVC – 3%
Fiberglass – 2%
Other – 7%

13. What percentage of your sanitary sewer system do you rehab and replace each year?

The average of our respondents was approximately 3.4 percent, with many selecting between 1 to 5 percent. Some responded as high as 10 percent.

14. What type of pipe achieves the longest life cycle?

As in our 2008 and 2010 surveys, PVC was chosen the most often by respondents, at 54 percent. HDPE and clay swapped second and third positions from 2010, with HDPE taking the second spot at 27 percent and then clay at 22 percent.

PVC – 54%
HDPE – 27%
Clay – 22%
Concrete – 10%
Fiberglass – 8%
Brick – 7%
Iron – 7%
Polymer Concrete – 2%
Steel – 1%
Other – 7%

15. What types of pipe do you use for trenchless projects?

Like our 2008 and 2010 surveys, HDPE garnered the top spot, at 63 percent in 2012, followed by PVC at 39 percent. The gap between HDPE and PVC has closed over our previous polls, which had HDPE at 68 percent in 2010 and PVC at 45 percent.

HDPE – 63%
PVC – 39%
Fiberglass – 11%
Concrete – 10%
Clay – 9%
Iron – 7%
Polymer Concrete – 7%
Steel – 6%
Brick – 1%
Other – 14%

16. Rate the importance of the following characteristics when selecting pipe material for a trenchless project (extremely important, important, not important at all):

In 2012, meeting standards and longevity/design life are tied for “extremely important” factors, with 75 percent of respondents selected them. In 2010, they were in a virtual tie with meeting standards getting 74 percent and longevity/design life, 73 percent. In 2012, they were followed by life cycle of cost (65 percent), ease to maintain and rehab (58 percent) and compatibility (50 percent).

	Extremely Important	Important	Not important at all
Compatibility with existing systems	50%	42%	9%
Ease of installation	49%	46%	5%
East to Maintain and Rehab	58%	37%	6%
Initial installation cost	43%	50%	6%
Life cycle of cost	65%	31%	35%
Longevity/design life	75%	23%	3%
Meets standards	75%	22%	4%
Price	37%	56%	65%

17. Does the type of pipe material required for a trenchless installation limit the use of trenchless techniques in your system?

Yes 19%
No 81%

18. What is the biggest problem you face with pipe when completing trenchless installations?

Making the proper connections finished first with this question with 58 percent, followed by expense at 28 percent. Among the “Other” responses were: pipe movement over time, soil conditions, various costs and bypass pumping.

Connections – 58%
Expense – 34%
Compatibility issues wtih existing system – 19%
Longevity – 5%
Twisting – 5%
Pipe availability – 4%
Pipe doesn’t meet local codes – 2%
Other – 18%