Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater 24 Error Fix: Abnormal Temperature Rise — Low Water Flow

The temperature rise across the heat exchanger is higher than the expected parameters, indicating restricted water flow. This is commonly caused by heavy scale (mineral/lime) buildup inside the heat exchanger tubes, particularly in hard water areas (above 7 grains per gallon hardness). Scale gradually narrows the internal passages, reducing flow rate while the burner continues at its normal firing rate. This results in the water absorbing too much heat in a single pass. Descale the heat exchanger — in hard water areas, annual descaling is recommended. Also check the inlet cold water filter screen (a small mesh screen at the cold water isolation valve connection) for debris that may restrict flow. Install and maintain a water softener or scale prevention device to reduce future buildup.

warning2 fixes available✨ Free fix available

Quick Answer

Error 24 on the Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater means: Abnormal Temperature Rise — Low Water Flow. The top-ranked community fix is “Descale the Heat Exchanger to Remove Mineral Buildup” (hard difficulty, ~90 min, DIY cost: $15-$20). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · water heater

Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.

When to Call a Professional

While many water heater repairs can be done safely at home, consider hiring a qualified technician if:

The repair involves electrical wiring, gas lines, or refrigerant
You've tried the top-ranked fix and the error persists
You smell gas, see sparking, or notice water leaking
The repair requires specialized tools you don't have
Your appliance is still under manufacturer warranty

Average professional repair cost for this issue: $150-$220.

Other Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater Error Codes

False Flame Detection

2 fixes

Abnormal Combustion — Blocked Vent

2 fixes

Ignition Failure — No Flame Detected

2 fixes

Flame Failure — Flame Lost During Operation

2 fixes

Thermal Fuse Activated — Overheat Safety

2 fixes

Overheating — Outgoing Water Too Hot

2 fixes

Condensate Drain / Vent Blockage

2 fixes

Outgoing Water Temperature Sensor Failure

2 fixes

People Also Ask About Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater Error 24

What does error code 24 mean on a Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater?

Error code 24 on the Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater means: Abnormal Temperature Rise — Low Water Flow. The temperature rise across the heat exchanger is higher than the expected parameters, indicating restricted water flow. This is commonly caused by heavy scale (mineral/lime) buildup inside the heat exchanger tubes, particularly in hard water areas (above 7 grains per gallon hardness). Scale gradually narrows the internal passages, reducing flow rate while the burner continues at its normal firing rate. This results in the water absorbing too much heat in a single pass. Descale the heat exchanger — in hard water areas, annual descaling is recommended. Also check the inlet cold water filter screen (a small mesh screen at the cold water isolation valve connection) for debris that may restrict flow. Install and maintain a water softener or scale prevention device to reduce future buildup.

How do I fix error code 24 on my Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater?

The most successful fix is "Descale the Heat Exchanger to Remove Mineral Buildup" (hard difficulty, ~90 minutes). Estimated DIY cost: $15-$20. HomeMD has 2 community-ranked fixes for this error.

Is error code 24 on a Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater serious?

This error is rated warning severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Can I fix Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater error 24 myself?

Yes — the top-ranked community fix ("Descale the Heat Exchanger to Remove Mineral Buildup") is rated hard difficulty and takes about 90 minutes. Tools needed: Adjustable wrench, Tankless water heater descaling pump kit.

How much does it cost to repair Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater error 24?

DIY cost: $15-$20. Professional repair typically costs $150-$220. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater have?

The Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater has 8 other known error codes, including: 05 (False Flame Detection), 10 (Abnormal Combustion — Blocked Vent), 11 (Ignition Failure — No Flame Detected), 12 (Flame Failure — Flame Lost During Operation), 14 (Thermal Fuse Activated — Overheat Safety), and 3 more.

What other error codes does the Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater have?

The Rheem Rheem RTGH-95DVLN Prestige 9.5 GPM Condensing Tankless Gas Water Heater has 8 other known error codes:

05 — False Flame Detection (2 fixes)
10 — Abnormal Combustion — Blocked Vent (2 fixes)
11 — Ignition Failure — No Flame Detected (2 fixes)
12 — Flame Failure — Flame Lost During Operation (2 fixes)
14 — Thermal Fuse Activated — Overheat Safety (2 fixes)
16 — Overheating — Outgoing Water Too Hot (2 fixes)
29 — Condensate Drain / Vent Blockage (2 fixes)
32 — Outgoing Water Temperature Sensor Failure (2 fixes)

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