Circulator Pump Buying Guide
There are several factors to consider when purchasing a circulator pump. These include
Horsepower, flow rate & head loss, material, connection method, features, and brand.
Horsepower or HP refers to the strength of the motor in a given pump. Horsepower is one of
the most important considerations when selecting a circulator pump. A pumps' horsepower
may vary from 1/40 HP for small pumps to several horsepower for large commercial pumps.
Horsepower directly affects the flow rate and head loss characteristics of a pump. Only within
the same brand does higher horsepower indicate a more powerful pump. For example, a Taco
pump with 1/6 HP does not necessarily have the same level of power as a Bell & Gossett pump
with 1/6 HP. When comparing pumps from different brands, you must consider both
horsepower and RPMs to choose a pump with the appropriate power based on gallons per
minute (GPM) and head loss of your system.
Flow Rate & Pressure Loss
The flow rate of a pump is defined as the gallons of liquid a pump can move in a minute (GPM)
given a certain head loss pressure. The appropriate pump will be able to reach the required
flow rate while overcoming the systems' head loss. A pump curve, which displays head loss
figures on the y-axis and flow rate on the x-axis, is commonly used to find the correct pump.
Circulator pumps may be constructed out of cast iron or bronze. Cast Iron pumps, such as the
Taco 007, are the most common in heating applications where oxygen-barrier PEX tubing is
used. With no oxygen barrier in the tubing, bronze pumps may be required in heating
applications to prevent rusting. In plumbing systems, bronze or stainless steel pumps must be
The most common way to connect a pump is with flanges. Flanges are used to make a threaded
or sweat connection between a pump and the supply pipe leading to it. Common sizes of
flanges are 3/4", 1", 1-1/4", and 1-1/2". Cast iron and bronze flanges are available and should
be purchased to match the material of the pump being used. Recent innovations in flanges
include shutoff valves and drains. These types of flanges may be purchased to ease installation,
but are not required. All major pump manufacturers make flanges along with Webstone, a
leader in flange production.
Pumps may also be connected using sweat or threaded connections. The pump will specify if it
may be connected in this manner.
Circulator pumps may come standard or with several additional features. The two most
common features are an integral flow check (IFC) or variable speed. The Taco 007-IFC is an
example of a pump that comes with an integral flow check. The placement of the flow check in
the pump ensures that it won't be needed elsewhere in the system. A variable speed pump
such as the Grundfos UPS-15-58 has the ability to operate at several different speeds. These
pumps are commonly used in radiant heat systems.
There are several major companies that manufacture circulator pumps. The leading US
manufacturer of pumps is Taco. Taco Pumps have become the industry standard, and there are
many different models available. Grundfos is another major brand of pumps. Grundfos pumps
have become increasingly popular with the introduction of their 3-speed pump. Other brands of
circulator pumps include Bell & Gossett, Armstrong, & Wilo.