Hot Tub pump frame sizes made easy

23 November 2021  |  Superior Wellness

Hot Tub pump frame sizes made easy

Hot Tub Pump Motor

Your pump is the beating heart of your hot tub. It is arguably the most important component as it does all the hard work in pumping your water around your system. Occasionally they do go wrong though, whether it is a mechanical error or just general wear and tear. But replacing your hot tub pump needn’t be a hassle. There are a few things to consider before choosing your new hot tub pump but get it right and your hot tub will be firing again in next to no time.

The main problem people have is making sure the pump frame size of your new pump is right for your hot tub. Take the time to get this right as spa pumps are expensive and you want to make sure it will fit snugly into your hot tub system and work correctly.

48 or 56?

All hot tub pumps are manufactured in one of two frame sizes: 48 frame or 56 frame. These numbers are arbitrary and don’t refer to any measurement but they do mean that a 48 frame will not work on a system built for a 56 frame and vice versa. It is all to do with size, with a 56 frame pump having larger dimensions between the through bolts than the 48 frame pump.

How can I tell the difference?

There are a few ways you can check to make sure you have the right pump for your hot tub, with nothing more that a ruler or tape measure. The first way to check, is to check the label on your existing pump. It should clearly state whether it is a 48 or a 56. It should say something like FR 56Y or 48Y. If it does, you can put your ruler away and choose your new pump. Job done.

If the label is not displaying the frame size or you just want to check to be doubly sure, you’ll need your ruler or tape measure.

Measuring your frame size

Remove your old pump, making sure it is all disconnected first. Now measure the distance between the through bolts on your pump. They run right through your pump, connecting your pump to the plastic wet end. If your pump has the wet end installed, go to the rear of the pump, the dry end, and you should see the bolt heads – if you can’t, you may need to remove the plastic cover.

Now you need to measure across or down from bolt to bolt, not diagonally, to check the size. If you measure 3 5/8” (91mm) then you have a 48 frame pump. If you measure 4 1/8” (104mm) then you need a 56 frame pump.

It’s that easy. As another general rule, 48 frame pumps are about 5 ½” (140mm) in diameter across the front and 56 frame pumps are 6 ½” (165mm).

Hot Tub Pump Frame Sizes Made Easy

Is that it?

Almost. Now you have the frame size there are a few other factors to consider before choosing a new pump, such as the voltage, the plumbing and the horse power. Please read our blog on pumps here and use your current pump specification as a guide to help you choose a new pump for your hot tub or spa. Failing that, get in touch and we can give you all the advice you will need to get your hot tub working again so you can get back to soaking in those bubbles.


Frame sizes do not relate to LX pumps, only Waterway Pumps and AquaFlo Pumps

AquaFlo - Only Wet Ends are available, there are no motors available or sold separately for AquaFlo

Useful Links

Hot Tub Replacement Motors

Link to Guides Page

Video - This video links you to youtube and includes the same content as above.

This article was written by Hot Tub Help Limited - All Rights Reserved 2021