Helpful Hints on Pumps

Hydrospares sell a huge range of pump makes & models to suit whirlpool baths, spa baths and hot tubs.

Before you buy a new pump we need to know what type you are replacing. We have put together this handy guide to help you identify the pump that you have.

Pump layout

Essentially there are 2 main sections: the wet end, which contains the impeller that moves the water; and the dry end, which is the motor that drives the impeller.    

Frame size

The size across the motor - generally either 48 frame (130mm) or 56 frame (147mm). 
Measure between the 2 fixing points, or check the motor label if available.  

If you have the space, choose a 56 frame motor. In the long run they are more reliable and more durable, as they stay slightly cooler while running. 


Spa pump motors are available in 1 speed or 2 speed versions.

A motor displaying a single RPM number will be a 1 speed; with two RPMs shown it will be a 2-speed. (Typically you will see 2800 for 1 speed or 2850/1425 for 2 speed.)


The horsepower is sometimes shown on the label. If not, we can look at the amp range of the motor to check it against the motor company’s information:

230 volts 7 – 8 amps = 1.5 HP (horsepower)
230 volts 9–10 amps = 2.0 HP
230 volts 10–11 amps = 2.5 HP
230 volts 11–12 amps = 3.0 HP
230 volts 14–15 amps = 4.0 HP

Wet End

Spa pump wet ends are either Side Discharge (where the outlet is offset to the side - the most common type) or Centre Discharge (where the outlet is centrally placed).

The diameter of the threads of the inlet (suction) and outlet (discharge) are measured as follows:

62mm = 1.5” suction
78mm = 2” suction
93mm = 2.5” suction

The discharge position refers to the orientation of the wet end (that is, where the discharge outlet is directed):

Pointing to left side - 9 o’clock
Pointing upwards  -12 o’clock
Pointing to right side – 3 o’clock 

Make & model

If there is the number 315-1220 embossed on the wet end rear, you have a Waterway pump (75% of the UK market).  An Aquaflo pump is very similar and the Waterway pump will replace it exactly.

Check our list of pump code numbers to view the different models available.

It’s important to choose the correct replacement pump and we want you to be happy with your purchase from Hydrospares.

We hope this information answers many common questions but for further enquiries please don’t hesitate to ring us on 01326 371 488 or email us on