Specification Guidelines

Category Question   Answer Date
Specification Guidelines Which is the best curing process?     There are three principal cure processes for mainline CIPP: hot water, steam and UV.  Of these three, there is not a best process.  Site conditions and pipe parameters may favor one process over the others, but it is often best to allow for multiple curing processes in the specifications and let the installer choose the best method for the installation at hand. Aug-15
Specification Guidelines Are there other methods of sealing at manhole and service connections?  Please provide examples of acceptable methods for sealing at lateral cut outs.   Methods used for sealing at manhole connections include hydrophilic seals, mechanical seals, CIPP point repairs, polymer treatments, cementitious treatments and grouting.  Methods used for sealing at service connections include CIPP full-wrap tees, CIPP brim style connections, grouting, polymer injection and excavation to install a factory connection. Aug-15
Specification Guidelines What is the typical warranty for CIPP?   Typical construction warranty for CIPP is one year. Aug-15
Specification Guidelines What are the recommendations for disposal of CIPP  curing water for waters with and without styrene?   Cure water with styrene should be cooled to 100 F and discharged to a sanitary sewer. Discharging hot cure water (temperature greater than 100 F) or cure water with higher than typical concentrations of styrene (from spilled resin, for example) to the environment can be damaging to aquatic life. Cure water without styrene should also be cooled to 100 F if discharged to a sanitary sewer. Because there are several types of resin without styrene with various chemical makeups, check with the resin manufacturer to see if cure water without styrene can be discharged to locations other than a sanitary sewer. Aug-15
Specification Guidelines Are there specific reasons to use a certain fabric or resin type? How do you determine which is best?   Difficult to answer that question in a few words.  For sanitary sewers, standard felt tubes cover most applications unless UV cure is utilized (fiberglass tube) or it is a medium to large sewer with high loadings. In this case, a reinforced tube may be required.  All three major resin types (polyester, vinyl ester & epoxy) are applicable to sanitary sewers, so often it comes down to price.  If the pH of the flow is on the high or basic end of the scale, vinyl ester or epoxy should be used.  For pressure pipes, vinyl ester or epoxy is preferred.  One way to handle this situation is to specify all the design parameters and let the installer choose the best product materials for the application. Aug-15
Specification Guidelines Is there some kind of "sealer" that can be installed in a newly installed pre-cast concrete manhole to prevent gas vapors from penetrating and causing a hazardous condition?    Not certain I understand the question, but if you are looking to prevent gas vapors from the sewer from penetrating the new manhole, polymer coatings may be the answer. Aug-15
Specification Guidelines Are the chemical grouting and cementitious grouting materials approved for use in sanitary networks near/adjacent to fish bearing tributaries?   When using a grout near fish bearing or potable water supplies, the chemical components need to be verified before use. There are a number of grout manufacturers that can provide specific information and recommend grout type usage for these area. Aug-15
Specification Guidelines Are the Parson MH inserts sealed to the MH lid?   No, they are not.  The flange of the insert rests on the lid seal of the frame that supports the cover.  When the manhole cover is removed, the insert will remain in place until it is removed by using the lifting strap. Aug-15
Specification Guidelines When do you use vinyl ester versus epoxy?   If either resin category is suitable for the project, if often comes down to cost.  For drinking water lines, currently only epoxy resin is certified to NSF 61 for CIPP.  For styrene free applications, the resin could be styrene free vinyl ester or epoxy, and often cost dictates.   Aug-15
Specification Guidelines Is it reasonable to expect a watertight sewer at the conclusion of the project?   For CIPP in mainline sewers, there should be no leakage through the wall of the CIPP.  If specified, manhole and lateral connections should be sealed.  As far as absolutely watertight, there may be a drop of water here or there leaking through. Going from 99% to 100% leak free may not be worth the effort. For CIPP gravity pipe leakage testing, allowable leakage from all sources in accordance with ASTM F1216 is 50 gpd/inch-diameter/mile.   Aug-15
Specification Guidelines What are guidelines for vacuum testing of rehabilitated manholes that have large pipe connections (+36")?   For testing manholes with larger pipe connections it is important to calculate the pressure that will be placed on the test plugs and determine that they can safely hold the vacuum during the test.  Aug-15
Specification Guidelines Who checks, within the year of installation, to verify performance? Consultant? Installer? Owner?   This procedure must be described in the contract.  The Owner should select at random the portions of the system to be inspected.  The actual inspection can be performed by the Owner or a CCTV contractor. Aug-15
Specification Guidelines What are the guidelines for specifying water cure versus steam cure?   Typically both cure systems should be specified.  The installer can then choose the proper installation and cure method for the project.  There are some general guidelines, such as long installations should be water inversion/cure ( generally >1000 ft.); steam cure works well for shorter, MH to MH installations; and over-the-hole or on-site installations should be water invert/water cure.  Nothing is set in stone, and these types of decisions can only be made when considering all project parameters. Aug-15
Specification Guidelines Who certifies the quality control inspector, manufacturer, or installer?   The inspector is certified through NASSCO's Inspector Training & Certification Program for CIPP.  The installer can be certified by the CIPP technology provider to install the CIPP product.  The manufacturer's products can be tested by third party test laboratories. Aug-15
Specification Guidelines Do you recommend Third Party inspectors for larger projects or at the least, the owner's representative should be required to either have NASSCO's ITCP MR , NACE or SSPC certifications?   For CIPP inspectors, we recommend either third party or owner employed inspectors certified by NASSCO's ITCP.  NACE or SSPC trained and certified inspectors can be retained for a project. Manhole inspection requires entry into a structure. If entry by the municipal inspector is prohibited  then a NASSCO and or NACE/SSPC certified inspector should be required on the project site Aug-15
Specification Guidelines What is the tolerance of flow through the pipe during CIPP, for instance if a homeowner discharges to the sewer by accident?   Ideally, there should be no discharge into the sewer through service laterals.  However, it does happen, and periodically a typical municipal discharge through the lateral can be tolerated.   Aug-15
Specification Guidelines Are there any issues with making new taps to an existing line that has a liner installed? What special precautions may be required to the inside liner when the tap is made to the pipe?   New taps can be made to sewers previously rehabilitated with CIPP by using factory made connectors such as insert-a-tee.  As far as precautions, follow manufacturer's instructions. Aug-15
Specification Guidelines For MHs, are there different products for lining MHs if the MH is subject to a very corrosive environment (i.e., H2S gas turning to sulfuric acid)?   Highly corrosive environments typically call for a polymer or CIPM type coating material that will stand up against the H2S. The quality of the installation is extremely important requiring more frequent inspections to assure that no failure has occurred Aug-15
Specification Guidelines Shouldn't it be 50% failure of the original 10% test area to increase the testing?   If 100 manholes are rehabilitated. 10% or 10 manholes should be selected for testing. If 5% or more of those manholes or 1 manhole fails than an additional 10% or 10 manholes should be selected for testing. The process continues and if applicable, all manholes are tested.  Aug-15
Specification Guidelines Can you describe the process of determining minimum wall thickness?  Does it vary from manufacturer to manufacturer or is it a standard calculation?  Can this also just be "performance spec'd" by calling for minimum strength properties?   For circular CIPP, minimum wall thickness is determined by the design models found in the Appendix of ASTM F1216.  For egg shapes and ovals, the WRc equations (UK Sewerage Rehabilitation Manual) are used.  For other shapes, structural engineering principals or FEA can be used.  This process should be similar for all CIPP manufacturers.  Yes, you can specify the design parameters (depth, groundwater, live loads, etc.) and the CIPP minimum physical properties and let the installer or installer's engineer complete the thickness design. Aug-15
Specification Guidelines Please provide a minimum leakage rate for CIPP test.   For gravity sewers, the allowable water exfiltration rate (ASTM F 1216) is 50 US gallons per inch of internal pipe diameter per mile per day. Aug-15
Specification Guidelines It was stated to take a sample for every line section installed. Is this necessary for 8"-12" pipe for projects with numerous segments?  What cost is associated with each sample?    It is wise to sample each installation just in case there is a problem with a particular installation.  Not all samples have to be tested; maybe test one out each five installations, for example, and store the other samples.  There is no set way to do this; totally depends on what is described in the contract. Depending on what tests are specified and the test lab used, testing should cost about $200 - 300 per sample. Aug-15
Specification Guidelines Who is responsible for periodic inspections. Is it spelled out in the contract?   This should be described in the contract.  Typically it is a third party consultant or Owner employee. Aug-15
Specification Guidelines Is there a maximum flexural modulus of elasticity?  High flexural modulus of elasticity will lead to increase in brittleness.   No. It is true that by definition, as the flexural modulus increases, the material becomes less flexible.  However, high flexural modulus CIPP materials are typically fiber reinforced which reduces any negative effects of brittleness.  Have not seen this to be an issue. Aug-15
Specification Guidelines Are different warranty durations recommended for coating materials vs. lining technology?   Coatings are typically applied against corrosion protection. In order to protect the structure the coating must be entirely monolithic with no defects. It is important to discover defects in the coating and make the repair therefore additional inspections over a longer period of time are typically required therefore extending the warranty period longer than a liner installation Aug-15
Specification Guidelines Ovality - it stated 2% or as indicated. Should 2% be the minimum % even if it appears to be 0, or is it so difficult to tell that 2% is used?   Possibly both.  Unless a laser profile is completed, it is difficult to tell 0% vs 1% vs 2%.  Many designers default to 2% even if the pipe looks round. Aug-15
Specification Guidelines Under Performance Specs, are the contractors typically pre-qualified and, if so, what is an ideal way to pre-qualify contractors?   Prequalification does not necessarily occur with performance specifications.  It may or it may not. In the prequalification process, a submittal package is required prior to the bid.  The package is reviewed, and the contractor (or product or process) is either approved or rejected.  Bids are accepted only from those approved through this process. Aug-15
Specification Guidelines Please provide recommend method to remove CIPP thickness sample and repair of CIPP for host pipe greater than 18-inches but too small for man entry, especially for host pipe below water table.   A core sample, typically at the 12:00 o'clock position, should be removed either robotically or by reaching into the CIPP from a manhole.  If reaching into the CIPP, the core sample should be taken as far from the manhole as possible.  The core hole can be repaired by filling with a rapid curing polymer or by applying a polymer adhesive to the removed core and gluing it back into place.  This procedure can become problematic if groundwater enters through the core hole.  In this case, the flowing groundwater should be stopped by grouting before repairing the core hole.  As can be seen, this can lead to a very expensive core for thickness testing. Another approach is to verify that the correct dry tube thickness, resin quantity and installation procedures were utilized.  If so, the result should be the desired finished thickness. Aug-15
Specification Guidelines How can the engineer insure the felt tube manufacturer will overdesign the tube thickness to meet the installed minimum thickness in the performance spec?   It is up to whoever orders the tube (generally the CIPP installer) to order a tube thick enough to yield the minimum required thickness. The tube manufacturer may help with this decision. The engineer could ask that this information be submitted as a part of the Performance Work Statement (PWS), and then the inspector can verify that the correct tube thickness has been shipped to the job site.  For example, if the minimum design thickness is 16.2 mm and the contractor submitted a dry tube thickness of 18 mm in the PWS, the inspector can verify that an 18 mm tube was wet out with the correct quantity of resin. Aug-15
Specification Guidelines Please define a major wrinkle.   Don't think there is an official definition of "major wrinkle", but one that could cause potential operation and/or maintenance issues would be one definition. Aug-15
Specification Guidelines How is water tight defined? ASTM F1216 has an allowance for infiltration, doesn´t it?   The allowance is to cover all leakage including any leakage in the testing apparatus.  Old sewers may not be round, and there may leakage around plugs, for example.  Even though ASTM F 1216 does have a leakage allowance, it also states in Paragraph 8.7 that "No infiltration of groundwater should be observed."  Aug-15
Specification Guidelines Recent discussions with a group of Engineers indicates that most people are familiar with and use the lump sum bid process which has some limitations. The performance specifications lend themselves to using the request for proposal process (RFP). This allows the owner more latitude in evaluating contractors and products. Generally, it also allows the owner to select someone other than the low bidder if it can be shown that the higher bidder is providing a better deal for the owner. I believe people should be made aware of the availability of this process.    Agreed. The evaluated bid process has been successfully used with CIPP.   Aug-15
Specification Guidelines When reviewing references, is there a rule of thumb for what ranges of pipe sizes are considered similar? i.e., is installing 18" CIPP significantly different than 24" or 36"?   One or maybe two pipe sizes smaller or larger than the subject sewer could be considered similar.  In your example, 24" would be similar; 36" is not. Aug-15
Specification Guidelines Is there a list of commonly encountered defects?   There is a list of CIPP defects in NASSCO's Pipeline Assessment Certification Program Manual (PACP).  This list was compiled for the purpose of coding defects when inspecting a sewer rehabilitated with CIPP.   Aug-15
Specification Guidelines Can Owner specify method of curing (steam or water) in the Contract by pipe size and material?   Yes, the Owner can specify this.  However, it is typically better to leave the installation means and methods to the contractor. Aug-15
Specification Guidelines What are the typical warranty for CIPP materials?   See No. 5. Aug-15
Specification Guidelines Do you recommend requiring the Contractors Work Plan with the bid submittal and prior to award of the project?   Typically not.  The Performance Work Statement (PWS) is a submittal requirement for the successful bidder.  For prequalification, you could require that a brief PWS be submitted as a part of the contractor prequalification process.  This would occur well before the bid date. Aug-15
Specification Guidelines Are the other miscellaneous. specifications available on the NASSCO site (i.e. the pipe cleaning, pipe bursting, folded pipe ...)?   Yes. Aug-15
Specification Guidelines What would cause cipp to shrink after install?   There could be a number or reasons, but typically the CIPP has not fit tight enough up against the host pipe to develop an interference fit.  Upon cooling, the CIPP wants to shrink, which it can do if it is not "locked in" to the host pipe.  This is typically not an issue when rehabilitating old sewers with cracks, offset joints and so on.  Overheating and improper cool down can increase the risk of shrinkage. High risk applications are smooth, straight sewers with few defects and any plastic or plastic lined sewer. Aug-15
Specification Guidelines Do you recommend air testing of CIPP installations?   Low pressure air testing CIPP in a sewer setting can be difficult because of variable temperatures in the newly installed CIPP and setting up a leak-free testing apparatus in a sewer that is no longer round.  However, many air tests have been successfully performed on CIPP.  If the project has a large number of installations, you may consider air testing the first two or three installations, and, if successful, test maybe one in five or ten for the remainder of the project. Aug-15
Specification Guidelines Do you feel that use of a new, cementitious resurfacer throughout the entire manhole surface provides for a greater chance of (bond) success with epoxy-based coatings?   It is typical better to use a polymer based resurfacer (repair material) that is compatible with the polymer surface material. That being said the surface of the repair material must be properly prepared to provide a mechanical bond or be applied during the recommended recoat window for achieving a chemical bond. Using a cementitious resurface has been successfully used but will require strict adherence to manufacturers recommendations. Some issues that need to be addressed include:  1. Repair material must be compatible with the surface material. 2. Repair material must be sufficiently cured as recommended 3. Repair material mix ratio should not be changed in the field by adding additional water 4. Repair material surface must be prepared so as to provide for a mechanical bond with the surface material.                                                                       Aug-15
Specification Guidelines How long is a typical installation procedure (for planning sewage bypass purposes).   This is totally dependent upon the sewer and field parameters of each installation, especially considering the number of service laterals that must be reconnected.  Air inversion/steam cure of 300 ft. of 8" CIPP may take two of three hours, not counting service lateral reconnections, whereas 1,500 ft. of 72" (water invert/water cure) may take four or five days considering that the tube is wet out on the job site. Aug-15
Specification Guidelines In your opinion does staining after install mean that there is a defect causing water to leak in?   It can.  Brown streaks running vertically down the CIPP wall are often an indication of an active leak or a leak that has since sealed. Stains can be for other reasons, but stains caused by leaks are generally fairly easy to identify. Aug-15
Specification Guidelines Better testing than holiday for spray in liners?   For pin holes, spark or holiday testing should be performed. Aug-15
Specification Guidelines Is uniform thickness of a coating a critical criteria for a successful holiday detection test?   The holiday detection equipment is typically calibrated to a specific coating thickness (generally 100 -125volts per mil of thickness. The equipment is set-up for the minimum thickness acceptable. Before the actual structure is tested a test sample should be prepared to calibrate the testing equipment. Thickness is therefore critical when the coating is applied thinner than specified requirements. Aug-15
Specification Guidelines Please comment on the water tightness test for CIPP as defined by Institute for Underground Infrastructure (IKT).   In the IKT leakage test, developed in Germany principally by/for UV cure installations, a sample collected in a manhole is tested by placing a half bar vacuum on one side of the sample to see if dyed water applied to the opposite side can be drawn through the sample, indicating a leak.  Advantage: Fairly easy to collect the sample and conduct the test.  Disadvantage: The actual installed CIPP is not tested. Aug-15