Hayward Pool Heater BD Error: Blower Drain Fix

Quick Answer

Hayward BD is a blower drain or bypass fault appearing primarily on condensing H-Series models. On condensing units, a blocked condensate drain is the most common cause - condensate backs up into the combustion chamber and triggers the BD safety lockout. On non-condensing models, BD relates to the combustion air pressure switch circuit.

I usually see this code pop up during the humid months when algae growth is at its peak. If your heater starts up but dies after ten minutes, the condensate is likely backing up because it has nowhere to go. This safety lockout prevents acidic water from damaging your expensive burner tray or heat exchanger.

HaywardPoolheaterSeverity: moderateDifficulty: intermediate72% DIY Success

Time to Fix

20–90 min

Difficulty

intermediate

Parts Cost

$10 – $45

Tools Needed

Phillips #2 screwdriver, Flathead screwdriver

What Does the BD Code Mean?

What catches many pool owners off guard is that the heater might run fine for a few minutes before the BD code hits. It takes time for the condensate to pool up high enough to trip the sensor. If you hear a gurgling sound coming from the cabinet, you can bet the drain is plugged.

Most Likely Causes

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

Condensate drain tube blocked by debris, algae, or algae growth40%

Combustion air pressure switch fault or failed sensing tube24%

Combustion blower running abnormally14%

Condensate trap filled and overflowing12%

Vent restriction creating back-pressure10%

Symptoms You May Notice

BD code on the display, sometimes flashing and sometimes solid, usually showing up mid-cycle
Heater fires up and runs fine for anywhere from 5 to 15 minutes, then cuts out right as the pool temp starts climbing
Water puddling underneath the heater or dripping from the base of the cabinet during or after a run cycle
Gurgling or bubbling sounds from inside the cabinet while it's running
Pool temperature stopped rising even though you can hear the heater trying to cycle back on

Can you reset a Hayward poolheater to clear the BD code?

Once you have cleared the blockage or swapped the switch, cycle the power at the breaker or press the Mode button to Standby. Wait about 30 seconds before turning it back to Heat. I recommend staying by the unit for one full cycle to make sure the drain is actually flowing.

Tools Required for Diagnosis

Phillips #2 screwdriverFlathead screwdriverMultimeter with continuity modeStiff wire or straightened coat hangerGarden hoseShop vac (optional but really helpful)Bucket for condensate waterFlashlightSafety gloves and eye protection

Diagnostic Checklist

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

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
Combustion air pressure switchCHXPRS002 · $20–$45	CHXPRS002	$20 – $45
Condensate drain tube kitCheck model-specific parts diagram · $10–$25	Check model-specific parts diagram	$10 – $25

Frequently Asked Questions

What does BD mean on a Hayward pool heater?

BD stands for blower drain fault. In the field, I treat it as a drainage or airflow warning depending on what model you've got. For condensing units, it means the internal condensate plumbing is backed up with water that has nowhere to go. For standard units, it means the combustion air pressure switch isn't seeing enough airflow from the blower. Either way, the heater stops itself so it doesn't run in an unsafe condition. It's a safety lockout, not a random glitch.

How do I clear the condensate drain on a Hayward pool heater?

Find the drain port at the base of the cabinet and pull the rubber hose off. I usually grab a shop vac and suck out whatever's in there first. If you don't have a vac, a piece of heavy-duty weed trimmer line works surprisingly well for snaking the line. Once it's flowing, flush it with a garden hose for a full minute. Then mix a cup of bleach with a gallon of water and pour that through the trap. It kills the algae that caused the clog and buys you another season before it comes back.

Why does my Hayward heater show BD only after running for a few minutes?

Classic symptom of a partial clog, not a full one. The heater starts up fine because the drain pan is empty. But as it runs and creates condensate, that water starts accumulating. If it can't drain fast enough, it eventually rises to the level of the sensor and triggers the safety lockout. Full clogs throw the code immediately at startup. So the delayed onset, where it runs 5 to 10 minutes and then dies, almost always means partial restriction in the trap or drain tube. Clear the drain and flush the internal trap and you're usually done.

Is my Hayward H-Series a condensing model?

Standard H-Series models like the H400FDN and H250FDN are non-condensing. You can tell for sure by looking at the bottom of the cabinet for a drain fitting or a small PVC pipe. If there's nothing there, you've got a standard unit. Condensing models have a secondary heat exchanger that squeezes more efficiency out of the combustion process, and that process produces liquid water as a byproduct, which is exactly why they need the drain. Standard units just vent the hot exhaust straight out without cooling it enough to produce runoff.

Can I prevent BD from recurring on my Hayward heater?

Yeah, pretty easily. For condensing units, flush the drain line every spring before the season starts. Mix a little bleach with water and run it through the trap. Takes five minutes. For standard units, squeeze the rubber sensing hose between the blower and the pressure switch every spring. If it feels stiff or crunchy, replace it before it cracks mid-season and leaves you without a heater on a holiday weekend. A little bit of maintenance every spring and you probably won't see BD again.

How much does it cost to fix a Hayward BD error code?

Depends on the cause. If it's just a blocked condensate drain, you're looking at maybe $0 in parts if you do it yourself, or a $100 to $150 service call if you have someone come out. Replacing the rubber sensing hose is a $3 to $10 part and takes maybe 10 minutes. A new combustion air pressure switch runs about $40 to $80 for the part and it's pretty straightforward to swap yourself if you're comfortable with basic wiring. Blower motor replacement is where it gets pricier, usually $150 to $300 in parts alone, plus labor if you're not doing it yourself.

Related Hayward Poolheater Error Codes

Code: HUBHayward Pool Heater Error Codes Guide Code: AOHayward Pool Heater AO Error Code Code: RESETHow to Reset a Hayward Pool Heater

Models Known to Experience BD Errors

This repair applies to most Hayward poolheaters with this error code. Common model numbers include:

H150FDN, H200FDN, H250FDN, H300FDN, H350FDN, H400FDN, H400FDP, H250FDP

Written by

Raj Patel

HVAC & Water Systems Specialist · 15 years experience

Last verified for technical accuracy on March 14, 2026