A solar contractor is installing a non-potable closed-loop solar thermal system. The system uses a heat transfer fluid that is not water. According to the Uniform Plumbing Code (UPC) and California Plumbing Code (CPC), what is the primary requirement for a non-potable solar thermal system to prevent contamination of the potable water supply?
- ARegular testing of the heat transfer fluid for chemical composition.
- BInsulation of all non-potable piping to prevent heat loss.
- CInstallation of a temperature and pressure relief valve on the solar collector.
- DUse of backflow prevention devices or an approved indirect waste receptor.
Show answer & explanationAnswer & explanation
Correct answer: D. Use of backflow prevention devices or an approved indirect waste receptor.
The primary concern with non-potable solar thermal systems is preventing the heat transfer fluid (which may be toxic) from contaminating the potable water supply. The UPC/CPC mandates the use of approved backflow prevention devices, such as double check-valve assemblies or reduced pressure principle backflow preventers, or an approved indirect waste receptor with an air gap, to ensure there is no cross-connection between the non-potable and potable systems.
Why the other options are wrong
- A. While fluid testing might be part of maintenance, it's not the primary code-mandated physical barrier against contamination.
- B. Insulation is for efficiency, not for preventing contamination.
- C. A T&P valve is a safety device for over-temperature/pressure, not primarily for preventing cross-contamination.
Non-Potable Solar Thermal Cross-Contamination
UPC/CPC requirements to prevent heat transfer fluids from non-potable solar thermal systems from contaminating the potable water supply, primarily through backflow prevention or air gaps.
- Non-potable fluids can be toxic.
- Requires backflow prevention devices.
- Or an approved air gap with indirect waste receptor.
- Critical for public health.
Memory trick: Non-potable fluids, a backflow device intrudes, or an air gap, no more rude!