Replacing Galvanized Steel Pipes Using CIPP and Sliplining
While the zinc coating of galvanized steel pipes helps prevent the pipe from corroding, decades of use does cause erosion of the coating and buildup of rust on the inside of the pipe.
The health of a home lies in its plumbing system, simply because it delivers potable water for drinking and cleaning; two major activities that constitute a clean and healthy home. Unfortunately, a majority of our plumbing is in a state of deterioration owing to age and drawbacks of pipe materials. The flint crisis brought this matter to the forefront, forcing people to take a closer look at their plumbing systems.
The First Use of Galvanized Steel Pipes
Most homes built prior to the 1960’s and some even as late as the 1980’s used galvanized steel pipes for their plumbing system. While galvanized pipes are inherently good and have many benefits, the drawbacks are also cringe-worthy.
Most of us buy old homes for their use of sturdy building materials and wise utilization of space. However; it’s in these homes that the plumbing system is usually made of galvanized steel; some may even contain portions of lead and copper pipes. Obviously, that was the best available at that time and much information about the side effects of these materials, with the exception of copper, was not known, and not as widely publicized as it is today in the age of the internet.
Replacing these old pipes is not an easy task, nor is it light on the pocket. It’s a grand bit of investment but that should not deter us from buying these homes, modern construction isn't very comparable to these classic old homes full of character. On the plus side, a home with a good plumbing system will fetch higher prices in the real estate market compared to that of a faulty, low pressure, leaky plumbing system.
Trenchless technology has brought with it some amazing rehabilitation techniques that eliminate the need for replacing your pipes. These techniques not just reduce the time involved in rehabilitating the plumbing system but also cost much less. Two of these techniques that are great for rehabilitating galvanized steel pipes are the cured-in-place pipe method (CIPP) and sliplining. (Read on in "Using Trenchless Technology to Replace City Lead Pipes.")
Why Replace Galvanized Steel Pipes?
Galvanized steel pipes are made by dipping steel pipes into molten zinc. This coating helps prevent the pipe from corroding, however; decades of use does cause erosion of the coating and a buildup of rust corrosion on the inside of the pipe. Moreover, galvanized pipes began to be used after it was discovered that lead pipes could cause lead poisoning due to leaching of lead into drinking water.
In some places, galvanized pipes were used to replace portions of lead pipes that had deteriorated. Again, that did not solve the problem of lead leaching.
Copper pipes soon began to replace galvanized pipes but proved to be very expensive. Replacing damaged sections with copper pipes would not solve the problem, but aggravate it, because mixed copper and galvanized pipes would accelerate corrosion, and when pipes start to corrode, lead can be released into the water.
Galvanized pipes have a lifespan of anywhere from 25 to 40-years, but that may be reduced in areas where there is hard water. Detecting problems in these pipes can be tricky because they look fine on the outside. Corrosion begins on the inside of these pipes, and over time, the buildup will reduce water pressure and deliver contaminated water. (More in "The Lifespan of Steel, Clay, Plastic & Composite Pipes.")
These pipes can be replaced using CIPP and sliplining that dramatically increase the lifespan of the pipe without removing them.
Cured-in-Place Pipe (CIPP)
CIPP is one of the most used techniques in trenchless rehabilitation because of its ease-of-use and a design lifespan of at least 50-years. It creates a pipe within a pipe. Structural soundness is an inherent property of the liner material, eliminating the need to rely on the host pipe for strength.
The flow property of the material used for CIPP rehabilitation greatly offsets the minimal reduction in diameter of the pipe after installation. Problems such as tree root intrusion, inflow/ infiltration, cracks, gaps and offset joints can all be easily remedied using CIPP. For the duration of the installation, the pipe is taken out of service and is restored as soon as curing is complete, which may be a few hours at the most.
The Installation Process of CIPP
The CIPP technique involves the use of a liner material made of synthetic fabric such as non-woven polyester or fiberglass with a polyurethane coating on the exterior. This liner is impregnated with a calculated amount of thermosetting resin prior to insertion.
Before insertion, the host pipe is thoroughly cleaned of debris and protrusions. The CIPP liner is inserted into the host pipe by inversion or is winched into place. Once the insertion is complete, the liner is inflated using pressurized air or water until a close fit is obtained within the pipe.
After the liner is fully inflated, hot water or steam is circulated to begin the curing of the thermosetting resin. The liner is then slowly allowed to cool to prevent shrinking. The new pipe restores the flow of the pipe to maximum pressure and prevents further spread of corrosion or leaching of lead into the potable water. Since CIPP is a trenchless method, the process can be carried out from a single entry and exit pit without the need to dig up the lawn or remove floor tiles.
Sliplining is one of the oldest methods of trenchless rehabilitation. The pipe materials used for making the sliplining pipes are high-density polyethylene (HDPE), fiberglass reinforced plastic (FRP), polyethylene (PE) and polyvinyl chloride (PVC). These materials are inherently strong and have a lifespan varying from 50 to 70-years.
The sliplining technique requires slipping a smaller diameter pipe into the host pipe. The process can be carried out as continuous sliplining or segmented sliplining. An alternate connection may have to be provided until the process is complete. After the host pipe is cleaned of debris, the lining pipe, or carrier pipe, is joined using butt fusion, spigot joining or extrusion welding.
Depending on the method used, the pipe is either pulled, as in the case of welded pipes, or pushed into place, as in the case of gasket jointed pipes. The annular space between the host pipe and the new pipe is filled with grout and the ends are sealed. Service and lateral connections can be made after providing a relaxation period of 24-hours. This method can cause considerable reduction in the diameter of the pipe, but the lining pipe has flow characteristics that will compensate for the loss in pipe diameter.
Written by Tabitha Mishra | Civil Engineer, Technical Content Writer
Tabitha has a Bachelors Degree in Civil Engineering from Mumbai University, India, and is currently freelancing as a technical content writer. Prior to writing, she has worked as a site engineer and site manager for various building construction, building rehabilitation, and real estate evaluation projects.
Tabitha is also certified as a Primavera project management professional and is well versed with Auto CAD. In her spare time, she does private consultation for small-sized home builders and assists with plans and permissions.