sewer pipeline or sewerage pipeline

Would one say:

The sewer pipelines are old and need to be replaced. or ...

The sewerage pipelines are old need o be replaced

additionally:

The sewer infrastructure ...

The sewerage infrastructure

any help?

Solution 1:

A sewer is

An artificial, usually underground conduit for carrying off sewage or rainwater.

so a sewer pipeline is a slightly redundant term, only necessary to distinguish a sewer pipeline from some other kind of sewer.

Sewerage is

1. A system of sewers.
2. Removal of waste materials by means of a sewer system.
3. Sewage.

so unless you have the third meaning fixed in other parts of your conversation it again seems unnecessary.

You could call it a sewage pipe

Liquid and solid waste carried off in sewers or drains.

in the same way as you might have a water pipe or a gas pipe. Infrastructure is mush word that serves no purpose here. I myself would just go with sewer:-

The sewers are old and need replacing.

Solution 2:

A sewer is an underground channel for taking away waste water. So a sewer pipeline is an underground pipeline that serves as a sewer (or perhaps a pipe that connects directly to the sewer).

Sewerage is the whole drainage system that uses sewers. So you never need to use the word infrastructure; you can just say sewerage. A sewerage pipeline can be any part of the sewerage system, so it is more general than sewer pipeline.