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Maintenance Checklist:

How Mike Keeps Weil-McLain Cast-Iron Boilers Running for 25+ Years**
The Truth: Cast Iron Doesn’t Die of Old Age — It Dies From Neglect

Let me cut straight to the point:

**A Weil-McLain CGA-5 isn’t a “15-year boiler.”

It’s a 25–35 year boiler — IF you maintain it the Mike way.**

Cast-iron boilers don’t have delicate aluminum exchangers.
They don’t have fragile sensors that die when the moon is in the wrong phase.
They don’t rely on a computer to breathe.

They rely on:

combustion stability
draft stability
clean water
proper pressure
adequate circulation
correct temperature rise
minimal air entrainment

If ANY of those go sideways, the boiler suffers.
If ALL of those are kept in line, it becomes the hydronic equivalent of a diesel locomotive.

This is EXACTLY how Mike keeps CGA-5 boilers running long after newer “high efficiency” boilers have hit the scrap pile.

1. Annual Combustion Test — The Heartbeat of the Boiler

I don’t care if the flame “looks good.”
Your eyes cannot measure:

CO
CO₂
O₂
flue efficiency
draft stability
excess air
burner alignment

Combustion needs an analyzer.

The [Flame Efficiency Diagnostic Sheet] shows that combustion drifts 2–6% per year on atmospheric boilers due to:

burner dust
orifice fouling
gas pressure variance
chimney temperature swings

If you don’t tune the flame annually:

efficiency drops
soot builds
flue temperatures fall
condensation increases
chimney decay accelerates

A CGA-5 with a bad flame is a car with a clogged carburetor — it will run, but badly.

2. Clean the Burners and Pilot Assembly — Small Dirt = Big Problems

Atmospheric burners are simple, but not magic.
Dust, lint, rust flakes, and spider webs (yes, spiders LOVE gas burner tubes) cause:

lazy flame
yellow tips
high CO
delayed ignition
popping sounds
rumble on startup

The [Burner Tube Airflow Restriction] confirms that partially blocked burner tubes increase CO output by up to 300%.

Every year:

remove burner tray
vacuum dust
brush burners lightly
clean pilot orifice
check thermocouple position
tighten pilot hood
confirm stable flame

This takes minutes and prevents thousands in repairs.

3. Verify Draft & Chimney Operation — The Silent Boiler Killer

Draft problems destroy atmospheric boilers faster than anything.

Poor draft causes:

CO spillage
pilot outages
burner instability
condensation in flue
rust flakes dropping into burners
soot buildup
chimney mortar failure

The [Chimney Draft Degradation and Seasonal Flow Report] shows draft weakens significantly in:

cold chimneys
oversized flues
blocked liners
negative pressure basements

Every inspection MUST include:

draft test with instrument
visual flue check
chimney cap inspection
connector slope verification
spillage test at draft hood

If your installer doesn’t test draft?
They’re not a boiler tech.

4. Flush the Low-Water Cutoff (LWCO) — The Device That Saves Your Boiler’s Life

Cast-iron boilers crack when run dry.
That’s why the LWCO exists.

But if the LWCO isn’t flushed?

It:

fills with sludge
sticks
misreads water level
fails during emergencies
exposes the boiler to dry firing

The [Sludge Contamination Bulletin] shows LWCOs in older systems begin sticking after just 6 months of sludge accumulation.

Every heating season:

check LWCO
flush until water runs clear
test life-saving shutdown
verify electrical response

This is NON-NEGOTIABLE.

5. Expansion Tank Check — The #1 Cause of Relief Valve Leaks

A dead expansion tank turns your system into a pressure bomb.

Symptoms:

relief valve dripping
boiler pressure rising to 30 psi
fluctuating temperature
noisy pipes
spitting air vents

The [Hydronic Pressure Stabilization and Air Removal Log] confirms over 80% of pressure issues come from failed diaphragm tanks.

Check annually:

tap tank — hollow = good, solid = waterlogged
measure pressure charge (12 psi cold)
check Schrader valve for leaks
inspect tank orientation (must be vertical)

Replace tanks that fail pressure checks immediately.

6. System Water Quality — The Hidden Cause of 75% of Cast-Iron Failures

Cast iron is tough, but NOT invincible.

Bad water causes:

magnetite sludge
corrosion
blocked radiators
circulator damage
uneven heating
boiler hot spots

The [Cast-Iron Corrosion Pattern Ledger] reveals that untreated boiler water accelerates internal casting wear by 30–50%.

Every year:

test pH (should be 8.0–9.0)
test hardness
check for iron oxide
confirm water clarity
flush if contaminated
add inhibitor if needed

Water is the lifeblood of hydronics.
Treat it with respect.

7. Bleed Air & Purge Zones — Air Is the Enemy of Circulation

Air causes:

cold radiators
cavitating circulators
banging pipes
reduced flow
high return temps
low heat output

The [Air Migration and System Entrapment Behavior Field Note] shows that air re-enters older systems constantly, especially in:

multi-story homes
homes with panel radiators
systems with long returns

Every fall:

purge each zone
bleed radiators
confirm auto-vent operation
check air separator condition

Air sneaks in constantly — removing it is ongoing maintenance.

8. Check Circulators & Zone Valves — The Real “Weak Links” of the System

CGA-5 boilers rarely fail.
Circulators and zone valves fail all the time.

The Hydronic Component Stress & Annual Wear Pattern Chart found:

circulators average 8–12 years
zone valves average 7–10 years
actuator motors fail far earlier

During annual maintenance:

verify pump amperage
check bearings
check flow checks
listen for cavitation
test zone valve motors
test end switches
confirm proper opening/closing

A dead circulator can make a perfectly good boiler look “broken.”

9. Inspect the Pressure-Reducing Valve (PRV) & Backflow Preventer

Your system pressure should be:

12–18 psi (cold)
18–25 psi (hot)

If pressure is drifting?

Your PRV is sticking.

If your PRV sticks open?

You flood the system.
You blow relief valves.
You crack radiators.

If it sticks closed?

Your boiler runs dry.

The Backflow & Feed Valve Reliability Analysis shows PRVs begin drifting after 5–7 years, especially in hard-water homes.

Annual testing is mandatory.

10. Clean the Boiler Sections — Flush Out Soot & Improve Heat Exchange

Even atmospheric boilers accumulate:

soot
rust flakes
scale
combustion debris

These insulate the cast-iron sections, reducing heat exchange.

The Cast-Iron Section Temperature Stress Behavior Ledger confirms section fouling increases metal stress by raising surface temperature differentials.

Every maintenance cycle: