What does Rinnai error code 25 mean?

Rinnai titles code 25 Condensate pump error or drain is clogged (accessory pump). The diagnostic manual explains that the code only appears when the condensate safety switch contacts are made, meaning the two wires touch. That happens when condensate backs up and trips the float switch in the pump. It can also happen if the condensate pump simply stops working. Rinnai lists it for both the SENSEI series and the older non-SENSEI models.

Two details matter here:

• The code belongs to the accessory pump. Rinnai's manual describes a condensate pump as something used when there is no floor drain available or when the drain sits above the level of the heater's condensate outlet. If your heater drains straight to a floor drain with no pump, you are unlikely to see code 25.
• The pump is wired to the heater on purpose. Rinnai's installation manual says a condensate pump, if installed, should be wired to deactivate the water heater if the pump fails. The two white wires labeled for the condensate pump safety switch connect to the normally open contacts on the pump. So when the pump's float rises, the heater shuts down. The code is the system working as designed.

### How does Rinnai test that safety switch?

The installation manual includes a test that shows what the code is doing. The installer unplugs the pump and fills its reservoir with water until the float switch closes the circuit. With the water heater on, it displays code 25. Then the pump is plugged back in, the reservoir empties, and the installer turns the water heater off with the On/Off button, waits five seconds, and turns the power back on to clear the code. That last sequence is the reset for a code 25 once the cause is fixed.

Rinnai's diagnostic manual lists five steps for code 25:

1. 1Confirm power is supplied to the pump.
2. 2Check the pump for proper operation. Rinnai notes this is an external, third party pump.
3. 3Ensure the drain line is not clogged or frozen.
4. 4Check all wiring for loose, damaged or broken connections.
5. 5Ensure the drain line has an air gap in it.

The short owner-facing table in the same manual's operation section reduces this to two: confirm the wire connections and wiring are good, and confirm the condensate reservoir is empty and the pump is operating.

### Which of these can I look at without tools?

Steps 1, 2 and part of 3 are within reach, as long as the heater is off:

• Is the pump plugged in and is its outlet live? A pump with no power cannot move condensate, and Rinnai's first step is to confirm power.
• Is the reservoir full? If the water is at the float and the pump is not running, the pump is the suspect. If the pump is running and the water is not going down, the discharge line is the suspect.
• Is the discharge line kinked, disconnected or full of debris? Look along its length for a bend, a pinched hose or a joint that has separated.

Rinnai's installation guidelines add what a good drain looks like, and they help you spot a problem by eye. The drain pipe should be corrosion resistant, such as PVC pipe or plastic hose. It should slope toward the floor drain or the pump, be as short as possible, and be at least the same diameter as the heater's half inch connection along its whole length. Its end should be open to the atmosphere and should not sit under water or other substances. Rinnai's diagram marks a line ending under water as not correct.

Rinnai's guidelines contain a few "do nots" that homeowners and handymen often break:

• Do not connect the condensate line to the pressure relief valve line. Rinnai says both must be plumbed independently to drain.
• Do not connect it to an air conditioning evaporator coil drain.
• Do not add an external condensate trap. The heater has an integrated trap. Rinnai says the trap primes itself during operation as condensate forms, and that condensate draining from the heater indicates the trap is full and there is no blockage in the drain. You do not need to add water to it.
• Do not leave the line unprotected where it can freeze. Rinnai says lines in areas subject to freezing should be wrapped with an approved supplemental heat source, and that for outdoor units the line should run through an interior wall or between insulation and an interior wall. Freezing is a smaller risk in the Valley than in colder states, but it is on Rinnai's list for outdoor lines.

Rinnai also offers a condensate neutralizer kit that raises the pH of the condensate before it reaches the drain, and notes that condensate has to be disposed of according to local codes. If your setup has a neutralizer, its media is one more place a blockage can form, and a technician can check it.

Both involve condensate, but they point at different places. Rinnai's code 10 lists a full condensate trap among its causes, along with air supply and exhaust blockages, and it is not tied to the pump. Code 25 is tripped by the accessory pump's float switch on the disposal side. If you have a pump and see code 25, start at the pump. If you have no pump and see code 10, the trap and the vent are the places to start. Our page on Rinnai error code 10 covers the second case.

### What if the code clears but keeps coming back?

A code that clears after you empty the reservoir and returns a few days later is telling you the drain is still marginal. The usual explanation is a partial restriction, a discharge line with a low spot that holds water, or a pump that runs but cannot keep up. Write down how long it took to return and whether the reservoir was full when you found it. Those two facts tell a technician whether to look at the pump, the discharge line or the heater's own trap. Keep in mind that Rinnai's guidelines call for a downward pitch on the whole line, so a sag anywhere along it is a fault.

Call if the pump has power but will not run, if the discharge line needs to be rerouted or re-sloped, if the code comes back after you clear it, or if water is on the floor near the heater. A pump that has failed needs replacing, and a drain that cannot reach a drain or a pump properly needs plumbing changes. Also call if you smell gas at any point. Leave, do not touch switches, and call Southwest Gas at 877-860-6020 or 911.

HQ Plumbing and Air is licensed and insured, with emergency service 24/7. We give free estimates and upfront pricing before we start. To see the whole list of codes, visit our Rinnai tankless error code list. For a heater that stops for other reasons, our page on common tankless water heater problems is a good next stop, and Rinnai error code 14 covers the overheat side.