The best way to assure obtaining the correct replacement pump, is to remove the old unit prior to ordering the new one. This will allow inspection and measurement to assure a correct match.

After disconnecting the electrical power, remove the spa’s access panel.

Some spas will have two gate or slice valves installed at either side of the pump (1). If so, close these valves prior to removing the pump. If no valves are present, drain the spa.
Disconnecting the Old Spa Pump

  • Disconnect the bare copper bonding wire from the pump’s ground terminal.
  •  Unscrew the pump’s two unions. Some residual water will drain out.
  • Remove the mounting screws from the pump base bracket.

Although the pump’s power cable is still attached to the control system, the pump can now be lifted out of the equipment bay.

The old power cable will be used for the replacement pump, if  in serviceable condition.

Remove the cable, making a note of wire color codes and connections. Make sure the wire ends are clean for a good connection to your new pump. If necessary, snip off an inch or two, and restrip the wires. Most spa pumps are two speed units, with the low speed used for filtration and heating cycles.  Two speed 240V pumps have 4 wires: red, black, white, and green. Red is normally low speed, and black high speed. The white wire is common and the green is ground.

Determine Pump Voltage & Horsepower for your replacement pump.
While all 110-120V spas use 120V pumps, not all spas wired for 220-240V use 240V pumps. Some use 120V pumps. So check your owner’s manual, and look at the label on the old pump to determine the voltage. The label should also indicate the horsepower and amperage. See pump specification below for a cross reference.
Some people desire to increase the jet action by upgrading to a larger pump. This is generally not a problem if the spa’s control system and the electrical service can accommodate the added amperage. As a rule of thumb, do not increase the pump horsepower more than one level of magnitude. For example, upgrading a 1 HP pump to 1.5 HP, or a 3 HP pump to 4 HP is reasonable. Avoid jumping from 2 HP to 5 HP as such a radical increase may cause problems like cavitation, uncomfortable jet pressure, or excessive current draw.

Determine Form Factor: Side or Center Discharge for new pump replacement.
The two spa pump form factors refer to the outflow or discharge fitting on the Wet End.  Your old pump will be either Center Discharge or Side Discharge.

In most cases you need to match the existing discharge to get the components to match up.   Side Discharge  is more efficient than a Center Discharge pump of the same horsepower.

Motor Frame Size
The physical size of the spa pump motor is referred to as frame. Spa main pumps will have a size of either 48 frame, which are approx. 5.5″ diameter, or 56 frame, which are approx. 6.5″ diameter.  Check the old motor’s ID plate for frame size or you can easily determine a motor’s frame size by measuring the spacing between the through-bolts.  Bolt spacing on a 48 frame motor will be less than 4 inches.  Whereas a 56 frame motor’s bolts will be spaced more than 4 inches apart.
Note: Because of their lower cost and compact size, most spa pumps in service are 48 frame. Larger 56 frame motors are a little more expensive and somewhat stronger. They tend to operate a bit cooler than 48 frame units, which can mean longer service life.

Determine Pump Plumbing Size by measuring O.D. of Male Wet End Threads
Plumbing size is very important, but a lot of people get it wrong and end up ordering the wrong pump.  Most spa pumps use either 1.5″ or 2″ plumbing fittings, and a few have 2.5″ intake suction. These are pipe call-out sizes, not fitting measurements.  With the pump unions removed, measurement is simple. The easy way to get it right for most brands of hot tub pumps is by measuring the overall outside diameter (O.D.) of the pump’s threads:
1.5″ Pump thread measures approx. 2-3/8″ O.D.

2.0″ Pump thread measures approx. 3″ O.D.

2.5″ Pump (intake) thread measures approx. 3-5/8″ O.D.
Note: These pumps normally have a 2.0″ discharge thread fitting, which measures approx. 3″ O.D.

Now we know what size pump is the right pump for your hot tub and can replace yours very quickly to get you back into your hot tub once again.