CSLB C-46 Solar ContractorSolar Thermal System InstallationMedium
A solar thermal system installer is positioning a flat-plate collector on a sloped roof. To ensure proper drainage and prevent air pockets, what is the MINIMUM recommended pitch for a horizontal collector header?
- A1/16 inch per foot
- B1/8 inch per foot
- C1/4 inch per foot
- D1/2 inch per foot
Show answer & explanationAnswer & explanation
Correct answer: B. 1/8 inch per foot
A minimum pitch of 1/8 inch per foot is generally recommended for horizontal piping in solar thermal systems (and plumbing in general) to ensure adequate drainage of fluid and proper purging of air.
Why the other options are wrong
- A. This pitch is often insufficient for reliable drainage and air purging.
- C. While better for drainage, 1/4 inch per foot is not the minimum and may be harder to achieve consistently on a roof.
- D. This is an excessive pitch for horizontal headers and is typically not required or practical.
Collector Header Pitch
The slight slope applied to horizontal piping (headers) in a solar thermal collector array to facilitate fluid drainage and air purging.
- Crucial for preventing stagnation and air binding.
- Ensures complete drainage when the system is shut down or for maintenance.
- Standard minimum is 1/8 inch per foot.
Memory trick: To drain the pipes and clear the air, 1/8 inch per foot, beyond compare.