CSLB C-36 Plumbing ContractorService, Repair, and MaintenanceMedium
A client reports that their tankless water heater is producing lukewarm water and occasionally shuts off. The unit has been regularly maintained. Which of the following is the most likely cause of this issue?
- AA faulty temperature and pressure (T&P) relief valve, causing pressure buildup.
- BSediment buildup in the heat exchanger, restricting water flow and heat transfer.
- CA clogged condensate drain, preventing proper exhaust of combustion byproducts.
- DAn undersized gas line, leading to insufficient fuel supply for maximum heating.
Show answer & explanationAnswer & explanation
Correct answer: B. Sediment buildup in the heat exchanger, restricting water flow and heat transfer.
Sediment buildup in the heat exchanger is a common problem in tankless water heaters, especially in areas with hard water. It restricts flow and reduces heat transfer efficiency, leading to lukewarm water and potential shutdowns. While other issues can occur, this is the most direct cause of the symptoms described for a regularly maintained unit.
Why the other options are wrong
- A. A faulty T&P valve primarily causes water leakage or potential safety hazards, not typically lukewarm water or shutdowns in this manner. It's a safety device, not directly involved in heating efficiency.
- C. A clogged condensate drain would typically cause error codes related to combustion or exhaust, and potential water leaks, but not directly lead to lukewarm water production or general heating inefficiency.
- D. An undersized gas line would cause consistent issues with reaching temperature, but the 'occasionally shuts off' part points more towards an internal operational issue like restricted flow rather than just insufficient fuel.
Tankless Water Heater Sediment Buildup
Mineral deposits (sediment) accumulating inside the heat exchanger of a tankless water heater, reducing efficiency and flow.
- Common in hard water areas.
- Causes reduced hot water temperature and flow.
- Can lead to unit shutdowns or error codes.
- Requires periodic flushing (descaling) for prevention and repair.
Memory trick: Sediment's slow creep, heat's lost in the deep.