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Replacement

The term “replacement” is used here to denote that a new pipe (or the full equivalent of a new pipe) is being installed in the same space that is currently occupied by the existing pipe. This can be important in crowded rights-of-way where space to install a new pipe on another alignment may be very limited. Readers should be aware that the terms “on-line” or “off-line” can be used differently in the literature describing pipe replacement. One usage differentiates replacement methods as to whether the pipe can be replaced while it is still in service (on-line) or needs to be taken out of service or bypassed (off-line). The other usage differentiates as to whether the replacement pipe is installed in the same position as the existing pipe (on-line) or in a new alignment (off-line).

Since many of the methods listed as "renovation" techniques are capable of being designed to function independently of the existing host pipe, it is possible that such techniques can be considered to provide a "replacement" of the existing pipe. This possibility is indicated in our chart classification but, for simplicity, all the renovation methods are not relisted in this section. The key distinction separating a replacement from a renovation is whether the liner installed can carry all the internal loads and external ground/groundwater loads without relying on the existing host pipe to carry some of the loading or considering it to provide an enhancement for the liner against buckling failure. 

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