Let’s get a few things straight:

Two pumps does not mean twice the jet pressure – it simply means there are two separate arterial systems, each pump assigned to different sections of the hot tub.   When only one pump is on, only half of the jets in the hot tub are activated, as the other half are controlled by a secondary pump.

The main benefit of a two-pump system is that you don’t have to activate all of the jets at once if you don’t want to.  One person can get a massage on one side of the tub while another person can sit in still water on the other side if they prefer it.

For a simple hot tub with fewer jets, a single pump will do the trick – for example, one 3hp pump for 24 jets is fine.  But for a 50-jet model, it would be better to have two 3hp pumps (one for each side of the tub), than one 6hp pump on a single arterial system.  For reasons beyond the scope of this webpage, this is better engineering.

In a two (or more) pump system, pump one (main pump) typically has a high and low speed.  The low speed is for filtration and heating (moves the water through a filter to clean the water and past the heating element to increase the temperature).  The high speed is for “massage mode”.  Pump two (secondary pump) doesn’t need a low speed, and typically only has a “high” and “off” mode.

Pump one turns on low speed mode on and off automatically whenever the hot tub needs to be heated up to reach the set thermostat temperature, and also every so often to circulate the water for filtration.  Pump two stays off most of the time, except at least once a day, to churn the water to prevent stagnation in the pipes. 

Circulation pump:

A “circ pump” is not considered to be a main pump – it’s an optional auxiliary small 24/7 low-flow pump on a dedicated short arterial system meant for filtration and heating the tub (NOT for massage).  

The main benefit of having a circ pump is that it’s quiet, so you don’t have to listen to pump one turn on and off to heat and filter.