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Installation Cost Breakdown:

What a Weil-McLain CGA-5 REALLY Costs in 2025
(Piping, Controls, Labor & Venting)**
Mike Breaks Down the REAL Cost of Putting a 133,000 BTU Cast-Iron Boiler in Your Home

Let me start with the truth every HVAC company hides behind “free estimates” and vague quotes:

**Installing a Weil-McLain CGA-5 is NOT cheap.

It’s NOT a fast job.
And it’s NOT just swapping a box.**

A 133,000 BTU cast-iron boiler weighs over 400 pounds, demands a gas supply that can feed a small restaurant, and needs venting, piping, wiring, and hydronic controls that are fundamentally different from forced-air systems.

This is NOT a furnace replacement.

This is hydronics — the engineering world of:

pressure
flow
thermal mass
BTU extraction
water chemistry
circulator head
near-boiler piping physics

Most installers underestimate the job.
Most homeowners underestimate the job.
And most quotes you see online underestimate the work by a mile.

Let’s break down exactly where every dollar goes — Mike style.

1. The Boiler Itself ($2,200 – $3,600)

The Weil-McLain CGA-5 Series 3 — 133,000 BTU natural gas boiler is:

heavy
durable
stable
simple
old-school reliable

But the equipment cost is only 25–35% of your total install.

What your boiler DOES include:

cast-iron sectional heat exchanger
atmospheric burner
gas valve
jacket
basic controls
limited warranty

What it does NOT include:

piping
controls
pumps
expansion tank
air elimination
venting
feeder/backflow
condensate neutralizer (if required by code)
wiring
chimney liner
drain/purge stations
zone valves

This is why “boiler-only” pricing is meaningless.

2. Old Boiler Removal ($500 – $1,200)

Removing a cast-iron boiler is work:

disconnecting gas
removing flue
draining system
cutting old near-boiler piping
hauling a 350–600 lb unit
cleaning the pad or floor
disposing of asbestos-era junk
cutting circulators or zone valves
isolating domestic water
safe disposal per code

The [Boiler Installation Labor and Complexity Assessment Matrix] shows removal labor on cast-iron boilers is one of the largest variables in the entire job.

Older boilers?
Worse every time.

3. Gas Line Upgrades ($300 – $1,200)

This is the part homeowners HATE to hear:

A CGA-5 needs a TRUE 133,000 BTU gas supply.

Not whatever pipe size your 1970s furnace used.

This means:

1" or ¾" gas pipe (depending on length)
proper regulators
correct manifold pressure
leak checks
drip leg
bonding/grounding
code-mandated shutoff valves

The [Gas Supply Sizing and Pressure Loss Field Analysis] shows that 80% of boiler underperformance is caused by gas starvation — not the boiler.

If your installer doesn’t put a manometer on your gas valve?

Send them home.

4. Chimney Liner Upgrade ($800 – $2,200)

Atmospheric boilers MUST vent properly.

Your old furnace probably shared the chimney with a water heater.
Your new boiler might not.

Most homes need:

stainless steel chimney liner
correct diameter
proper termination
draft hood assembly
combustion testing
draft verification
spillage testing

Why?

Because atmospheric boilers produce:

warm flue gases
less buoyant draft
moisture that condenses in cold chimneys

The [Draft Behavior and Chimney Liner Requirement Ledger] shows unlined chimneys cause:

flue condensation
masonry decay
draft failure
carbon monoxide spillage

A liner is NOT optional — it’s safety.

5. Near-Boiler Piping ($900 – $2,500)

This is where rookies ruin boilers.

Near-boiler piping includes:

supply/return manifolds
circulator pump installation
flow-check valves
air separators
expansion tank
purge stations
boiler bypass setup
pressure-reducing valve
backflow preventer
service valves
relief valve
gauge tree

Every fitting affects system flow, which determines:

heat transfer
emitter performance
cycle length
return temperature stability

The [Primary/Secondary Hydronic Piping Layout Guide] explains why wrong piping causes short cycling on cast-iron boilers — especially ones like the CGA-5 with high water volume.

Good piping = quiet, stable heat.
Bad piping = noisy, uneven, short-cycling disaster.

6. Circulator Pumps & Zone Valves ($250 – $1,200 per zone)

Your home may use:

zone valves
circulators
or both

New systems typically require:

high-head circulators
ECM pumps
flow check valves
isolation flanges
wiring harnesses

If your home has:

2 zones → add $500–$2,000
3 zones → add $750–$3,200
4 zones → add $1,200–$4,500

The [Circulator Performance Study] proves zone imbalance is one of the most common reasons homeowners think their boiler is “too small.”

7. Water Feeder, Backflow, & Safety Package ($250 – $650)

Every boiler must include:

automatic water feeder
backflow preventer
pressure-reducing valve
relief valve
pressure/temperature gauge

The [Residential Boiler Safety and Makeup Water Control Note] confirms that incorrect feeder setup is a top cause of:

boiler flooding
relief valve blow-off
pressure swings

Nothing fancy — but mandatory.

8. Air Elimination & System Purge Components ($150 – $500)

Air is the enemy of hydronics.

You need:

air separator
automatic vent
purge valves
boiler drains

Small parts, giant impact.

The [Circulator Cavitation Incident Report] shows air in hydronic systems destroys pumps faster than any other failure mode.

9. Thermostat & Control Wiring ($150 – $550)

Depending on your system:

existing thermostat wiring may be insufficient
multi-zone systems require multiple runs
priority zoning (e.g., indirect water heaters) needs dedicated wiring
control boards require low-voltage routing

Nothing crazy — but not free.

10. System Fill, Flushing & Commissioning ($300 – $900)

This is the step cheap installers skip — and the step that determines how long your boiler will live.

Proper commissioning includes:

system flush
leak check
pressure test
combustion analysis
draft test
gas pressure test
purge & bleed
delta-T verification
thermostat calibration
circulator adjustment

The [Hydronic Startup and Commissioning Verification Log] says improper startup is responsible for 40%+ of early boiler failures.

If your installer doesn’t use test instruments?

Walk them out.

11. Total Installation Cost — Mike’s REAL Ranges for 2025

These are the real numbers — not the fantasy numbers from “budget HVAC blogs.”

Basic Install (rare):

$6,000 – $8,500
(Single zone, short gas run, no liner needed)

Standard Install (most homes):

$8,500 – $12,500
(2–3 zones, chimney liner, new piping, upgraded gas)

Major Install (old homes, big zones):

$12,500 – $17,500
(full piping replacements, liner, multi-zone circulators)

Complete Hydronic Overhaul:

$17,500 – $25,000+
(entire system rebuild, pumps, valves, full near-boiler repipe)

These numbers align directly with patterns shown in the Boiler Installation Labor & Complexity Assessment Matrix]\ and the real hours/labor/material demands of cast-iron hydronics.

This is not furnace work.
This is skilled hydronic craft.