Rinnai Code 25: Bath Fill Error (ThermaCirc Models)

Quick Answer

Rinnai Code 25 is exclusive to models with a built-in bath fill or recirculation feature. The unit was commanded to fill a bathtub or run a recirculation cycle but did not detect that the operation completed within the set time window. Common causes include a flow rate that is too low to fill the tub in time, the bath fill timer set too short for the tub volume, a recirculation pump fault, or a valve that did not open properly during the cycle. This is a low-severity code because the water heater itself is functioning; the issue is with the bath fill feature's operation. Adjusting the bath fill time setting or increasing flow rate usually resolves the problem.

RinnaiWaterheaterSeverity: low85% DIY Success

Time to Fix

10–45 min

Difficulty

beginner

Parts Cost

$80 – $150

Tools Needed

Bucket and timer (for flow rate measurement), Screwdriver set

Wrong code?

Not seeing 25 on your display?

Select what your appliance is actually doing and we'll take you to the right guide.

bath fill or recirculation fault

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What Does the 25 Code Mean?

Bath fill or recirculation cycle did not complete in time. Only affects ThermaCirc or bath fill equipped models. Usually a timing or flow rate adjustment, not a hardware failure.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

Bath fill time limit set too short for the volume of the bathtub40%

Low water flow rate through the bath fill hot water line24%

Recirculation pump not operating or operating at reduced capacity14%

Scale buildup reducing flow through the supply piping to the tub12%

Bath fill valve or mixing valve not opening fully10%

Symptoms You May Notice

Code 25 on controller display after initiating a bath fill
Bathtub only partially filled when Code 25 appears
Bath fill feature worked previously but no longer completes
Normal hot water operation from showers and sinks is not affected

Can you reset a Rinnai waterheater to clear the 25 code?

Code 25 clears when you press the power button off and on or when a new bath fill cycle is initiated. No hard reset is required. After adjusting the bath fill time setting, the next bath fill attempt should complete without the code.

Tools Required for Diagnosis

Bucket and timer (for flow rate measurement)Screwdriver set

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

Access the bath fill time setting on the Rinnai controller

Access the bath fill time setting on the Rinnai controller. This is typically found in the Settings or Bath Fill menu. Review the current time limit. For a standard 60-gallon tub at 4 GPM, filling requires approximately 15 minutes. If your tub is larger or your flow rate is slower, increase the time limit accordingly.

Test the flow rate from the bath tub hot water faucet

If the unit has a ThermaCirc recirculation pump

Check whether the bath fill valve or tub fill mixing valve is

If flow rate and timing adjustments have not resolved Code 25

Replacement Parts

If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.

Part Name	OEM Number	Estimated Price
ThermaCirc Recirculation PumpContact Rinnai with model number · $80–$150	Contact Rinnai with model number	$80 – $150

Verify part fitment for your Rinnai model

Repair vs. Replace Calculator

Appliance Age (Years)7 Yrs

Labor Approach

Our Verdict

REPAIR

Estimated Cost: $115 (Parts) vs $1250 (New Machine)

Frequently Asked Questions

Which Rinnai models have the bath fill feature that triggers Code 25?

Code 25 appears on Rinnai models equipped with the built-in ThermaCirc recirculation system or the bath fill scheduling feature, which is available on the RUR series (condensing) and select RL series models when paired with the MC-91-2 or comparable controller. Standard RU and V series models without a recirculation pump will not display Code 25.

How do I change the bath fill time on my Rinnai?

On the MC-91-2 controller, access the Settings menu and locate the Bath Fill or Timer settings. The bath fill time can typically be set in increments from 5 minutes to 60 minutes or more depending on firmware version. Set the time to allow your tub to fill with margin, not exactly the minimum needed, to avoid triggering Code 25 due to minor flow variations.

Code 25 appeared but my bathtub is full. Why?

If the tub filled completely but Code 25 still appeared, the bath fill feature's flow sensor or completion sensor did not detect that the target volume or fill condition was met. This can happen if the flow sensor reading is slightly off, or if the bath fill cycle was completed a few seconds before the timer expired. Increasing the time limit slightly and retesting will usually eliminate the spurious code.

Does Code 25 affect my regular hot water for showers and sinks?

No. Code 25 is limited to the bath fill feature. Normal on-demand hot water for showers, sinks, and other fixtures continues to work unaffected when a Code 25 condition exists. You can continue using all other hot water normally while you diagnose the bath fill issue.

Can I disable the bath fill feature on my Rinnai to stop Code 25?

Yes. If you do not use the bath fill feature, you can disable it in the controller settings. Navigate to the Bath Fill or ThermaCirc settings menu and turn the feature off. This will prevent Code 25 from appearing. Normal hot water operation is not affected by disabling the bath fill feature.

Related Rinnai Waterheater Error Codes

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Same Fix on Other Brands

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Models Known to Experience 25 Errors

This repair applies to most Rinnai waterheaters with this error code. Common model numbers include:

RUR98iN, RU199iN, RU98eN, V65iN, RL75iN, RU160iP

Last verified for technical accuracy on March 14, 2026