Can I install a larger Waterway replacement pump in my hot tub to get more pressure at the jets?
This is a question that comes up a from time to time and the answer is NO, NO, NO! 2 Reasons why.
1. When your hot tub was designed and built the manufacture would have calculated the electrical load from all the equipment and designed it accordingly, and the hot tub would have been ULc, ETLc or CSA tested/approved based on that design as safe. If a larger jetting pump was installed, say a 5Hp when the original one was a 4HP this would overload the hot tubs control systems, a 5HP 240 volt motor draws about 4.4 amps more on high speed (See illustration below) then a 4HP. Also, it could overload the breaker and the wire to the hot tub creating a fire hazard.
2. The difference in the pump example of a 4HP to 5HP in water flow is approximately 40-50 GPM (Gallons per minute) the hot tubs hydraulics would have originally been design around the water flow and pressure of the original pump(s). If the pressure was increased it would overload the original design as well as cause the larger pump motor to work harder under stress trying to push a higher volume of water through plumbing then it was designed to and the motor could fail prematurely.
If your hot tub spa used to have good pressure at the jets and now it has less, then it will require some investigating to find out if there may be something restricting the intake at the filter reducing the water flow. Also check to make sure the jets (if adjustable) are turned all the way to the open position.