A long copper hot water main moves as it heats and cools. What does the IPC require of piping that is subject to expansion and contraction?
- Provision must be made for expansion and contraction, through devices such as expansion loops, offsets or joints, with supports arranged to permit the movement
- BAdditional rigid anchors must be installed until all movement of the piping is prevented, since a pipe that cannot move cannot work its joints loose or rub its supports
Holding the pipe still looks like the direct cure for a pipe that is moving. Restraint does not remove the thermal force, it relocates it into the joints and the structure, which is the failure the question describes.
- CSystem pressure must be reduced until the noise and the movement stop, because the ticking is the pipe shifting under the pressure carried through the anchored run
The noise invites a pressure explanation, which is the error path here. Expansion is a function of temperature change and pipe length, not of pressure, so reducing pressure would only degrade fixture performance.
- DInsulating the piping removes the need to make an allowance for movement, since insulation holds the line near a steady temperature year round
Insulation slows heat loss, protects against condensation and burns, and does moderate the rate of change. The pipe still swings between ambient and delivery temperature every time the system runs, so total movement is unchanged.
Why A is correct
The piping support provisions require that allowance be made for expansion and contraction, using expansion joints, loops, offsets or equivalent means, and that hangers and anchors be arranged so the pipe can move as intended. Anchors are placed deliberately to direct movement into the loop, not to eliminate it.
What this question is testing
The item tests understanding that thermal movement is a design condition to be accommodated, and the candidate's ability to identify the code-recognized means of doing so rather than field remedies that fight the movement.
On the job
Copper grows roughly an inch per hundred feet per hundred degrees of temperature change, and plastics move several times that, which is why the ticking above a ceiling almost always turns out to be a hot line dragging through a tight hanger. The fixes are simple if planned: a swing joint or offset at a change of direction, hangers that let the pipe slide, and isolators where the pipe passes through framing. Retrofitting them after the joints have been stressed is far less pleasant.
Memory technique
Let it move or it will move you.
Exam tip
For expansion questions, the right answer always gives the pipe somewhere to go.
Where to look it up
Chapter 3, Section 308, the expansion and support provisions. Support intervals and expansion requirements differ between IPC and UPC, and plastic piping in particular carries different rules, so verify against your adopted code.