The Taco 110-120 Series is an inline circulator pump family widely used in hydronic heating, boiler systems, and mechanical room applications. Known for their long service life, oil-lubricated bearings, and replaceable service components, Taco 110, 111, 112, 113, and 120 pumps remain among the most recognized inline Taco circulators in commercial and residential systems.
This article covers the full 110-120 Series product line, internal construction, service component categories, common failure modes, and what to look for when the pump needs attention. It is an educational reference for engineers, contractors, facility managers, procurement professionals, and students.
What Is A Taco 110-120 In line Pump Series?
The Taco 110-120 Series is a three-piece, oil-lubricated inline circulator. That three-piece design - motor, bracket, and pump body as separate assemblies - is central to its serviceability. When something fails, you replace only the failed component, not the entire pump. It is one of the main reasons the 110-120 Series has remained among the top pumps on the market.
Taco 110-120 Series - Model Variants and Specifications
The 110-120 Series is a family of models. Taco uses sequential model numbers to denote different HP ratings and flow/head characteristics, all of which share the same three-piece architecture and parts ecosystem. Standard models are cast iron, generally specified in closed-loop hydronic heating and cooling.
Stainless steel construction is available on request for potable water, domestic hot water, and open systems. To specify stainless steel, add the suffix 'S' to the model number (e.g., 110S, 111S). Stainless steel models carry the same pressure and temperature ratings and are certified to NSF/ANSI 372.
| Model | Body Material | HP | RPM | Max Temp. | Pressure | Weight |
| 110 | Cast Iron | 1/12 | 1725 | 240°F | 125 psi | 21 lbs |
| 111 | Cast Iron | 1/8 | 1725 | 240°F | 125 psi | 26 lbs |
| 112 | Cast Iron | 1/3 | 3450 | 240°F | 125 psi | 28 lbs |
| 113 | Cast Iron | 1/8 | 1725 | 240°F | 125 psi | 27 lbs |
| 120 | Cast Iron | 1/6 | 1725 | 240°F | 125 psi | 46 lbs |
All models share the same flange bolt pattern and most service components, which simplifies distributor stocking. All models are factory tested before shipment, rated to 125 PSI maximum working pressure, and certified to NSF/ANSI 372 in stainless steel construction.
Pump Curves
Internal Construction - How The Taco 110 Is Built
Understanding the Taco pump's internal construction makes parts identification and failure diagnosis significantly easier. The 110-120 Series uses a consistent internal design across all model numbers.
Motor
A resilient-mounted, single-phase motor with a built-in thermal overload protector for reliable operation. The motor is isolated from the pump body by rubber mounts, which make the 110-120 Series operate quietly. The motor drives the impeller via a spring coupler, reducing vibration and protecting both ends from shock loads.
Spring Coupler
The spring coupler connects the motor shaft to the pump shaft. It is a consumable wear item. After years of service, it can fatigue, leading to reduced torque transmission and lower pump efficiency. It is one of the first things to check when a pump runs but underperforms.
Bracket Assembly
The bracket assembly is the structural interface between the motor and pump body. It houses the bronze sleeve bearing and provides motor mounting geometry. The bearing is oil-lubricated; neglecting lubrication is the most common cause of premature bearing wear on the 110-120 Series.
Mechanical Seal
The two-piece carbon/ceramic mechanical seal prevents water from migrating from the wet end into the bearing and motor. A rotating carbon face rides against a stationary ceramic seat under spring pressure. Seal failure is the most common service issue on the 110-120 Series and is almost always the cause of a pump leaking at the shaft area.
Impeller
A one-piece non-ferrous impeller is pressed onto the stainless steel shaft. Not a routine wear item under normal conditions, but susceptible to damage from cavitation, debris ingestion, or incompatible fluids.
Pump Body and Gaskets
Three-piece cast iron or stainless steel (upon request and model code verification) body with flanged connections. A body gasket seals the wet end to the bracket assembly.
Service Components - What Is Replaceable and Why
One of the strongest arguments for specifying the Taco 110-120 Series is that virtually every component that wears or fails is individually replaceable. You are not discarding the entire pump when a seal goes - you are replacing one inexpensive component.
The categories of service components available for the 110-120 Series cover everything that is likely to wear over the pump's service life:
Seal kits
Contain the replacement mechanical seal faces and body gasket - everything needed to re-seal the pump wet end. This is the most commonly ordered service item for the 110-120 Series.
Impeller and shaft assemblies
Available for replacement when the impeller is damaged by cavitation, debris, or corrosion.
Spring couplers
The link between the motor shaft and the pump shaft. It's an important piece; a fatigued coupler is a frequent cause of reduced performance on older pumps.
Bracket Assemblies
Generally replaced when the pump's bronze sleeve bearing is worn. Available in cast iron for standard and alternate configurations.
Motors
Replacement motors are available based on the required power capacity and RPM. The pump design allows motor swapping without touching the wet end or the pipe.
Flanges / Connections
Available in sets by pipe size (3/4", 1", 1-1/4", 1-1/2" NPT). Notably cross-compatible with several other Taco series, making them a practical stocking item for service mixed Taco installations.
Gaskets
Body gaskets and flange gasket sets are available individually for low-cost leak repairs at the body joint or flange face.
Replacement Parts List
- 8 - Body
- 25 - Impeller & Shaft
- 29 - Seal
- 31 - Motor Assembly
- 36 - Flange Set
- 56 - Coupler
- 74 - Bracket Assembly
- 161 - Gasket Kit
Common Failure Modes - Overview
The following overview is provided to help engineers, students, facility managers, and procurement professionals understand how most pumps generally behave over time.
Every system is different. Actual diagnosis, disassembly, and repair must be performed only by qualified personnel, following manufacturer instructions and applicable safety codes.
With that context in mind, the following failure patterns are consistently reported across the inline pumps and are useful background when assessing a pump's condition or planning a service call.
Shaft Seal Leak
The most common issue in any pump. A steady drip from the area where the shaft exits the bracket is almost always a failed mechanical seal. Seals typically last 5 to 15 years, depending on water quality, temperature, system cleanliness, and the frequency of premature maintenance. Premature failure can result from running dry, excessive vibration from a worn spring coupler, or debris damage to the seal faces. A seal kit is the standard repair; consult the Liberty Supply sales team for the correct kit for your model.
Pump Runs But Delivers No or Low Flow
If the motor runs but the flow is not being delivered as desired, the most likely causes are:
- Fatigued spring coupler (slipping rather than transmitting torque to the impeller)
- Damaged or worn impeller
- Air binding (where the pump is circulating air rather than water)
For the first two causes, the replacement is mandatory to fix the flow issue. Air binding is common after system fill or maintenance and is resolved by bleeding the system - not a parts issue.
Motor Failure
The resilient-mounted motor is long-lived but will eventually fail due to winding insulation breakdown or thermal damage from repeated overload trips. A motor that hums but won't start often has a failed starting capacitor or a winding issue. Replacement motors matched to each HP rating are available through the Liberty Supply Website.
Bearing Wear and Noise
Grinding or rumbling during operation usually points to a worn bronze sleeve bearing — almost always the result of inadequate lubrication. Annual re-oiling is required and is frequently overlooked in the field. If the bearing is worn, the bracket assembly needs to be replaced.
Body or Flange Leaks
A leak at the flange face is typically a failed flange gasket. A leak at the joint between the pump body and bracket points to a failed body gasket. Both are low-cost repairs using standard gasket components.
Video credit: Fix It James
Frequently Asked Questions
All five are three-piece inline Taco circulators in the same family, sharing the same architecture and most service components. The 110 is 1/12 HP at 1725 RPM. The 111 is 1/8 HP at 1725 RPM. The 112 is 1/3 HP at 3450 RPM for higher flow and head applications. The 113 is 1/8 HP at 1725 RPM with a 2" maximum flange connection. The 120 is 1/6 HP at 1725 RPM, also with a 2" maximum flange connection, and is designed for applications that need the highest flow in the family - up to 68 GPM. All models are available in cast iron and stainless steel variants.
Almost always a failed mechanical seal. The two-piece carbon/ceramic seal degrades over time, especially in systems with poor water quality, high temperatures, or a history of running dry. The repair is a seal kit, widely stocked and covering all models in the 110 family. If the leak is at the flange face rather than the shaft area, the issue is a flange gasket, which is a different and equally straightforward repair.
Yes. The 110-120 Series uses oil-lubricated sleeve bearings that require annual re-oiling via the oil ports on the motor and bracket. This is the single most overlooked maintenance task on these pumps and the leading cause of premature bearing failure. It takes about 5 minutes and significantly extends service life.
Standard cast-iron models are not suitable for potable water or open systems due to concerns about iron contamination. However, stainless steel construction is available on request for all models in the series. Stainless steel models carry the same pressure and temperature ratings and share all the same service components as the standard cast iron versions.
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