Spa Pump Frame Size
Hot tub pumps come in two different frame sizes. There are 48 frame and 56 frame pumps. It mays say what the frame size is on the old pump label. If the label is unreadable while the pump is still installed in the spa, a pocket mirror, cellphone camera or digital camera may be held in to get a picture of the motor/pump label on which many required details for the replacement pump are noted.
This is in reference to the actual size of the pump. 48 frame pumps are smaller in size than 56 frame pumps.
A typical 48 frame pump is about 5 1/2 inches or 14cm wide. A typical 56 frame pump is about an ince wider or 6 1/2 inches = 16.5cm wide.
The holes where the 4 long bolts go through which attaches the wet end to the dry end can be an indicator of frame size because on the bigger pumps, these holes are further apart. The 48 frame pumps have bolt spacing of about 3 3/4" and the larger 56 frame pumps have bolt spacing of about 4 1/8" or so. This may also be indicated on the motor sticker.
Frame size standardization is an important part of being able to interchange motors among different motor manufacturers.
Note: The 4 long through bolts attached to the wet end go all the way through the motor. They require a 1/4” nut driver to remove but be careful! Just pull them out enough to free the wet end. If you pull them all the way out the motor it will come all apart in your hands! You won’t be getting it back together either
STEP 5: Identify Pump Frame Size 
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| 48 Frame | 56 Frame | |
Hot Tub Pump Vibration Isolation Mounting Pads
This hot tub pump motor mounting pad fits under most any hot tub spa pump and absorbs some of the vibration that the pump can cause. The vibration manifests itself into a low frequency rumble which travels quite far and can be annoying to neighbors as well as people you are trying to have a conversation with near the spa.
The hot tub mounting pad cushions the pump to reduce vibration transmission to the the spa floor. Many manufacturers just mount or bolt the pump right to the floor of the spa which can allow the entire floor of the spa to become a sound board, amplifying the low frequency vibration.
The mounting pads are sold as a spa accessory as well. Retrofitting a mounting pad may involve having to replumb some spas that do not have much variance in the hose or pipe.
Generally, if it is hose instead of rigid pipe that connects the pumps to the plumbing, many pumps can be raised up the 1/2 inch or so to accommodate the pump vibration pad.
Pump mounts can be used on any StaRite, Waterway, Ultra Jet, Vico or other hot tub pump motors.
The pump mount helps to reduce the natural system frequency and dissipate unwanted energy for quieter hot tub operation. Some call them shock mounts, motor mounts or isolation pads, but it all refers to the same thing which mounts between the pump and the mounting surface to absorb some of the hum.
If you hear a grinding noise, that may be the pump bearings and not the steady state vibration hum caused by acoustical coupling and amplification between the pump and the spa cabinet.
Generally the Frame size is either 48 Frame or 56 Frame with hot tub pumps.
