CSLB C-36 Plumbing ContractorPlanning and EstimatingHard
A client requests a plumbing system for a new custom home that emphasizes water conservation and energy efficiency for hot water delivery. The contractor is evaluating different hot water distribution system designs. Which of the following system types best meets the client's priorities for both water and energy savings?
- ADemand-controlled recirculation system with an on-demand pump and sensor.
- BContinuous recirculation system with a dedicated return line and no controls.
- CStandard branched parallel system with a large central water heater.
- DManifold system with individual PEX lines to fixtures and a tankless water heater.
Show answer & explanationAnswer & explanation
Correct answer: A. Demand-controlled recirculation system with an on-demand pump and sensor.
A demand-controlled recirculation system only circulates hot water when needed, significantly reducing energy waste from constant pumping and minimizing the amount of cold water run-off, thus saving both energy and water.
Why the other options are wrong
- B. Continuous recirculation systems are very energy-inefficient due to constant pumping and heat loss from the pipes.
- C. This system typically results in significant wait times for hot water and high water waste.
- D. While a manifold system can reduce wait times by shortening runs, it doesn't eliminate the initial slug of cold water and a tankless heater alone doesn't address distribution efficiency.
Demand-Controlled Recirculation System
A hot water distribution system that circulates hot water to fixtures only when activated by a sensor or button, minimizing energy and water waste.
- Reduces wait time for hot water at the tap.
- Significantly saves water by reducing cold water run-off.
- Saves energy by only operating the pump when needed, preventing continuous heat loss.
Memory trick: Demand for hot water, not constant circulation.