How much larger should sleeves be than the pipes passing through a foundational wall?

In plumbing installations, particularly when pipes pass through foundational walls, it is essential to ensure that there is adequate space between the pipe and the sleeve to allow for potential expansion, movement, and any required insulation or sealing. The guideline of making the sleeve two pipe sizes larger than the pipe itself provides sufficient clearance for these factors.

This extra space allows for the installation of insulation if needed, reduces the risk of corrosion at contact points due to movement, and facilitates any necessary adjustments during installation or post-installation maintenance. Additionally, having the sleeve appropriately sized can also accommodate potential thermal expansion of the pipe materials, which is crucial in preventing stress on the pipe and reducing the likelihood of leaks or failures over time.

The other options either do not provide enough clearance or lack the standardized requirement for installation, which can lead to complications in the long term. Thus, specifying that sleeves should be two sizes larger than the pipes ensures compliance with best practices in plumbing installation as outlined in relevant codes.