Tandem vs Double Seal by Jason Fletcher

Tandem - vs - Double Seal by Jason Fletcher, PE
Some specifications call for pumps with seals in tandem and others for a double seal pump. What is the correct terminology and which is better? According to the Fluid Sealing Association: Tandem Seals - two seals that are orientated in the same direction Double Seals - two seals that are orientated in the opposite direction Zoeller Company uses tandem seals whenever we offer a pump with more than one seal. The advantages to a tandem design include 1) two completely independent seals that do not depend on the other one for sealing, 2) seals orientated in this configuration can withstand much higher pressures in the pump casing when compared to a double seal pump. Companies that use the double seal arrangement usually limit the amount of head on the seals by making only smaller, low head pumps with this type seal. So the question is why use the double seal arrangement at all? It boils down to cost. A double seal costs less to purchase and install than a tandem seal, but as is the case most of the time, you get what you pay for. Zoeller Company and most of the rest of the industry agree that a tandem seal is a superior way of sealing a pump motor from the outside elements. This should shed some light on the two most popular debates in the pump industry. Should you need more assistance please call the Technical Service hotline at 1-800-928-PUMP.

Tandem - vs - Double Seal
by Jason Fletcher, PE

Some specifications call for pumps with seals in tandem and others for a double seal pump. What is the correct terminology and which is better? According to the Fluid Sealing Association:

Tandem Seals - two seals that are orientated in the same direction

tandem.gif (6081 bytes)

Double Seals - two seals that are orientated in the opposite direction

double.gif (5491 bytes)

     Zoeller Company uses tandem seals whenever we offer a pump with more than one seal. The advantages to a tandem design include 1) two completely independent seals that do not depend on the other one for sealing, 2) seals orientated in this configuration can withstand much higher pressures in the pump casing when compared to a double seal pump. Companies that use the double seal arrangement usually limit the amount of head on the seals by making only smaller, low head pumps with this type seal.
     So the question is why use the double seal arrangement at all? It boils down to cost. A double seal costs less to purchase and install than a tandem seal, but as is the case most of the time, you get what you pay for. Zoeller Company and most of the rest of the industry agree that a tandem seal is a superior way of sealing a pump motor from the outside elements.
     This should shed some light on the two most popular debates in the pump industry. Should you need more assistance please call the Technical Service hotline at 1-800-928-PUMP.