How to Fix Rheem Furnace Error Code 58: Water Sensed in Condensate Pressure Switch (Full Guide)

When this fault triggers, your furnace will enter a hard lockout mode for safety. You will likely notice the inducer motor running continuously while the igniter fails to glow, resulting in a lack of heat. You might also hear audible gurgling or “sloshing” sounds emanating from the inducer motor housing. While this code sounds technical, it is usually a result of a physical blockage that can be remedied with a systematic diagnostic approach.

Symptoms of Rheem Error 58

Identifying Error 58 involves observing both the electronic diagnostics and the physical behavior of the unit. As a senior engineer, I look for these specific indicators during a field call:

• Diagnostic Flash Code: The dual 7-segment display on the furnace control board will explicitly flash “58.” On older models, look for a specific sequence of amber or red LED pulses.
• Inducer Run-On: The draft inducer motor may kick on to purge the system, but the furnace will fail to proceed to the ignition sequence (no “click” of the gas valve and no orange glow from the hot surface igniter).
• Audible Fluid Dynamics: You may hear “chugging” or “gurgling” sounds. This is the sound of the inducer motor blades hitting standing water that has backed up into the collector box.
• Moisture in Tubing: Visible water droplets or “slugs” of water can often be seen inside the translucent vinyl pressure switch hoses. These hoses should normally be dry.
• Cold Air Circulation: Because the burners are locked out, the blower motor may eventually run to circulate air, but that air will be at room temperature, leading to a noticeable drop in home comfort.

What Triggers this Code?

What Triggers this Code? (Root Cause Analysis)

Error 58 is not a “random” electronic glitch; it is a response to a physical breach of the pressure sensing threshold. Here are the primary engineering failures that trigger this state:

1. Blocked Condensate Trap or Drain Line: This is the most common cause. High-efficiency furnaces produce several gallons of slightly acidic water per day. Over time, “white slime” (biological growth) or sediment can clog the internal plastic trap or the external PVC drain line. When the water cannot exit the furnace, it backs up into the inducer housing, where the pressure switch detects the change in static pressure or literal moisture intrusion.
2. Improper Vent Pitching: The exhaust (flue) piping must be pitched back toward the furnace at a rate of 1/4 inch per foot. If the pipe sags or was installed level, condensate will pool in a low spot. This creates a “trap” in the vent, causing air turbulence and forcing water back into the pressure switch sensing port.
3. Inducer Port Calcification: The small nipple (port) where the rubber pressure tubing connects to the inducer housing is very narrow. Combustion byproducts can create a tiny crust of scale or oxidation, which traps moisture at the port. Even a single drop of water trapped here can block the pressure signal, leading the board to throw Error 58.
4. Pressure Switch Diaphragm Failure: Inside the switch is a sensitive silicone diaphragm. If the furnace has been running with high moisture for a long time, the diaphragm can lose its elasticity or become “stuck” due to internal corrosion. At this point, even if the water is cleared, the switch remains electrically “open” or “closed” incorrectly.

How to Fix Rheem Error 58 (Step-by-Step)

Follow these steps in order. Safety Warning: Always disconnect the 120V power supply at the service switch and shut off the gas supply before removing the furnace cabinet panels.

1. Inspect and Clear Pressure Switch Tubing:
   Locate the translucent or black rubber hoses connecting the inducer motor to the pressure switches. Carefully pull them off the plastic nipples. If you see water inside, shake them out and use a can of compressed air or a small pump to dry them completely. Do not blow forcefully into the pressure switch itself, as you can rupture the delicate internal diaphragm.
2. Clear the Inducer and Collector Box Ports:
   Take a small paperclip or a 1/16″ drill bit (held by hand) and gently poke it into the plastic ports where the hoses connect. It is common to find a “scab” of minerals blocking these holes. Ensure the passage is completely clear so the switch can “sense” the internal pressure without interference from moisture-wicking debris.
3. Flush the Condensate Trap:
   Locate the plastic box (usually black or clear) inside the furnace where the drain lines converge. This is the condensate trap. Remove the hoses and the mounting screws to pull the trap out. Flush it in a utility sink with warm water and a mild bleach solution to break up “white slime.” If you cannot remove it, use a wet/dry Shop-Vac on the external end of the PVC drain pipe to suck out any obstructions.
4. Verify Flue Vent Pitch:
   Inspect the PVC exhaust pipe leaving the furnace. Use a level to ensure it maintains a consistent slope back toward the unit. If you find a sagging section, you must support it with perforated hanger strap to eliminate the “belly” where water is collecting.
5. Perform a Multimeter Continuity Test:
   With the power back on and a call for heat initiated, set your multimeter to AC Volts. Measure across the two terminals of the pressure switch. If you read 0V, the switch is closed (working). If you read 24V, the switch is open (failed/tripped). If the switch stays open despite the inducer running and the lines being clear, the switch is defective and must be replaced with the exact OEM Rheem part.
6. System Reset:
   Once the water is cleared and the lines are dry, replace the panels and restore power. The furnace should clear the 58 code automatically after a brief self-test.

How to Prevent Error 58

Preventative maintenance is the only way to ensure the long-term reliability of a condensing furnace. As an engineer, I recommend the following protocol:

• Annual Trap Flushing: Every autumn, before the heating season begins, the condensate trap should be flushed with warm water. This prevents the “sludge” buildup that leads to 90% of Error 58 occurrences.
• Condensate Neutralizer Maintenance: If your system uses a neutralizer capsule (to protect your plumbing from acidic water), ensure the marble chips inside haven’t dissolved into a fine powder, which can flow backward and clog the furnace internal drainage.
• Install a High-Quality Surge Protector: While Error 58 is usually mechanical, voltage spikes can damage the sensitive logic gates on the control board that interpret the pressure switch signal. A dedicated HVAC surge protector can prevent “ghost” codes.

FAQ

Frequently Asked Questions

Q: Can I bypass the pressure switch to get heat temporarily?
A: No. Never jump a pressure switch. This switch is a safety device designed to prevent the furnace from leaking carbon monoxide or causing a fire if the venting or drainage fails. Bypassing it can lead to the heat exchanger filling with water or improper combustion.

Q: Why does this error only happen when it’s extremely cold outside?
A: This is often due to a frozen condensate drain line. If your drain pipe exits the house or runs through an unconditioned crawlspace, the water can freeze, creating a plug. The water then backs up into the furnace, triggering Error 58. Insulating the external drain line or using heat tape can solve this.

Q: I cleared the water, but the code 58 remains. Why?
A: If the moisture was inside the pressure switch itself, the internal contacts may have oxidized, or the diaphragm may be waterlogged. Once moisture enters the “can” of the switch, it is very difficult to dry out completely. In this scenario, replacement of the pressure switch is the only reliable solution.