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Most likely you're working with pipes in a project that does not have types of pipes with fittings. To solve this, first open a new project with the Plumbing template. Then from the first project use Manage > Transfer standards > select the new project and then from the list do "Select none", then select categories related to Pipe, especially "Pipe Settings" and "Pipe types". That will bring into your project pipes with configurations. Then use those pipe types to do your work.
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