Rheem Hybrid A108: Condensate Blocked

The Short Answer: On Rheem hybrid heat pump water heaters, A108 means “Condensate Blocked: Unclog Line.” The control has sensed water backing up from the heat pump’s condensate drain, so it stops the heat pump and heats with the electric elements instead. Clear the drain line and the alert should not return. If the pan is dry and the line is clear, the condensate sensor itself may need replacing.

What A108 means

The heat pump section cools the air passing over its coil, and moisture condenses out, just as with an air conditioner. That water collects in a pan and leaves through a condensate line. Rheem’s hybrid Use & Care manual (opens in a new tab) lists A108 as condensate blocked and says the heating source defaults to the elements because of the drain blockage.

You will usually still have hot water, because the elements are heating it. The heater just costs more to run until the drain is fixed.

A108 is different from A107, “Water Detected on Floor,” which uses a separate leak sensor to warn of water in the drain pan under the tank. If you see A107, look for a leak from the tank or plumbing first.

Common causes

• Clogged condensate line, often from algae, dust, or debris.
• Kinked or crushed tubing, or tubing that runs uphill before it drops to the drain.
• Frozen line in an unheated garage or where the line runs outside.
• Failed condensate pump where the heater drains to a pump rather than a floor drain.
• Failed condensate sensor, when the pan is dry and the line flows freely.

What you can check safely

1. Note the alert and when it appeared.
2. Follow the condensate tube from the heater to where it ends. Look for kinks, sags that hold water, a disconnected end, or a frozen section.
3. If the tube ends at a condensate pump, check whether the pump is plugged in and whether its reservoir is full.
4. If the tube ends at a floor drain or standpipe, check that the end isn’t sitting under water.
5. Clear or straighten only the external tubing. Turn the heater’s breaker off before working near it.

Rheem’s manual also describes checking the pan under the top cover. If you aren’t comfortable with that, or you can’t find a blockage in the external line, call for service rather than removing covers.

What the technician will check

A technician will turn off power, open the top section, and inspect the condensate pan and its outlet for sludge or debris, then flush the line through to the drain. They check the slope and route of the tubing and whether a condensate pump is needed or working. If the pan is dry and the line is clear but A108 continues, Rheem’s manual points to replacing the condensate sensor. They will not leave the sensor disconnected; it is there to protect your floor and the heater.

How serious is it?

A108 is not an emergency, but don’t ignore it. The heat pump stays off while the alert is active, which raises your electric costs, and a backed-up pan can eventually overflow.

For other Rheem hybrid alerts, see Rheem heat pump water heater problems. For water you think may be coming from the tank, see why water leaks from the bottom of a tank.

Frequently Asked Questions

Q: Why do I still have hot water with A108? A: The heater switched to its electric elements. That keeps hot water flowing but uses more electricity until the drain is cleared.

Q: A108 came back in winter. Why? A: A condensate line in a cold garage or running outdoors can freeze. Rerouting or protecting the line usually solves it.

Q: Can I unplug the condensate sensor to stop the alert? A: No. The sensor protects against overflow. If it is faulty, it should be replaced, not bypassed.