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Understanding LX Hot Tub Pumps: Part Numbers, Variations, and Common Pitfalls

Understanding LX Hot Tub Pumps: Part Numbers, Variations, and Common Pitfalls

Posted by The Hot Tub Professor on Feb 13th 2025

LX hot tub pumps are some of the most commonly used pumps in the spa industry and can be found across many different brands of hot tubs. Their popularity comes from reliability, availability, and standardized designs — but that same standardization can cause confusion when it’s time to replace a pump.

This guide explains how LX pump part numbers work, how major spa manufacturers use the same pumps under different numbers, how to avoid common replacement mistakes, and why amperage matters more than advertised horsepower.

How LX Pump Part Numbers Work

Most LX hot tub pumps use part numbers that begin with WUA. Common examples include:

  • WUA100

  • WUA150

  • WUA200

  • WUA300

  • WUA350

  • WUA400

  • WUA500

The number following WUA represents the pump’s general horsepower class, but additional characters before and after the number provide critical details.

Breaking Down a Full LX Pump Part Number

Let’s look at a common example:

56WUA400II

Here’s what it means:

  • 56 → 56-frame motor

  • WUA → LX pump series

  • 400 → 4 horsepower class

  • II → Two-speed pump

So a part number like:

  • 56WUA300I

Would be a 56-frame, 3 HP class, single-speed pump.

You may also encounter 48-frame motors and different speed configurations. Even small differences in part numbers can significantly affect fit and performance.

Why Brand Names Make LX Pumps Confusing

Many major hot tub manufacturers use the exact same LX pumps, but assign their own proprietary part numbers. This makes it appear as though the pump is brand-specific, when in reality it is not.

Watkins / Hot Spring / Tiger River / Caldera / Solana Example

A very common example:

  • Watkins part number 1431601-03
    is the exact same pump as

  • LX 56WUA400II

The pump itself is identical — only the part number changes.

Jacuzzi®, Sundance®, and Dimension One® Pump Numbers

Other manufacturers often list both the LX number and their internal number on the same pump.

For example, a pump may be labeled:

  • 56WUA400II
    along with proprietary numbers such as:
    6500-352, 6500-365, 6500-367, or 6500-363

These additional numbers identify the manufacturer’s catalog listing, not a different pump.

A Critical Difference: Mounting Base vs. Clamp-Style Mounting

One of the most common replacement mistakes involves the mounting style.

Some branded versions of LX pumps do not include a standard mounting base. Instead, they use a separate base with a large worm-drive clamp that secures the motor. This design allows the pump to be rotated into more positions than a fixed-base pump, which is useful in tight equipment bays.

If you order a standard LX replacement without realizing your original pump used a clamp-style mount, the new pump may not fit correctly without re-mounting or plumbing changes.

This is one of the most frequent causes of incorrect pump orders.

Horsepower vs. Amperage: What Really Matters

This applies to all brands of spa pumps, not just LX.

Pump labels often advertise impressive horsepower numbers, but those numbers are frequently misleading. When choosing a replacement pump, amperage tells the real story.

Ignore the Advertised Horsepower on the Label

Do not select a pump based on the advertised horsepower printed on the motor.

Everybody lies about horsepower — amperage does not.

How to Read the Amperage on Your Pump Motor

Look at the motor label on your existing pump:

  • Two-speed pump: You will see two amperage values

  • Single-speed pump: You will see one amperage value

A typical two-speed label may look like this:

10.0 / 3.5

  • 10.0 amps = high speed

  • 3.5 amps = low speed

For replacement purposes, always use the high-speed amperage.

Real-World Horsepower Based on Amperage (230V Pumps)

For 230-volt spa pumps, these amperage values are reliable averages:

  • 8.0 amps ≈ 1 HP

  • 10.0 amps ≈ 2 HP

  • 12.0 amps ≈ 3 HP

  • 14.0 amps ≈ 4 HP

  • 16.0 amps ≈ 5 HP

These are averages — always match the amperage closest to your existing pump.

Do not go by what the motor claims for horsepower.

Why Upsizing Horsepower Can Damage Your Spa

Installing a higher-amperage pump to “gain power” can damage your spa’s electrical system.

Higher amperage can overload:

  • Control boards

  • Relays

  • Wiring

  • Plugs

  • Heater circuits

  • Even the pump motor itself

Here’s a real-world example:

  • Two pumps at 16 amps each = 32 amps

  • A 5.5 kW heater = approximately 21 amps

  • Total draw = 53 amps

Most hot tubs are on 50-amp breakers, which means this setup already exceeds the system’s capacity.

If you’ve been told you have a 5, 6, or 7 HP pump, you almost certainly do not.

Special Warning for 115V (Plug-N-Play) Hot Tubs

True 2 HP 115V pumps are extremely rare.

Installing a higher-amp pump in a 115V spa can:

  • Overheat wiring

  • Melt plugs

  • Damage control systems

  • Shorten motor life

Do not order a higher-HP pump thinking it will increase performance — it will only cause failures.

How to Determine Motor Frame Size (48 vs. 56 Frame)

Frame size must be matched correctly.

Measure the width of the motor across the back:

  • 48 Frame: approximately 5¾ inches

  • 56 Frame: approximately 6½ inches

Correct frame size ensures proper fit, alignment, and long-term reliability.

How SpaShopper Helps You Save Money

Major hot tub manufacturers do not make pumps. They buy pumps from manufacturers like LX and assign proprietary part numbers.

At SpaShopper, we convert those proprietary numbers into the correct LX pumps and parts based on:

  • Amperage

  • Frame size

  • Speed

  • Voltage

  • Mounting style

  • Wet end specifications

This allows you to get the same exact pump and parts for significantly less money.

Need Help Identifying the Correct LX Pump?

If you’re unsure which LX pump or replacement part you need, help is available.

  • Text clear photos of your pump or label

  • Call or email our hot tub parts experts

  • Get confirmation before you order

? Text photos: 772-800-5445
☎️ Call: 844-500-4645
✉️ Email: dvillanueva@spapartsnet.com

About the Author

Written by The Hot Tub Professor

The Hot Tub Professor has over 25 years of hands-on experience in hot tub and spa repair, troubleshooting, and diagnostics. Known for practical, real-world solutions, he has helped countless spa owners and technicians avoid costly mistakes and get spas running correctly the first time.

Important Disclaimer

SpaShopper is not affiliated with, endorsed by, or connected to Jacuzzi®, Sundance®, Dimension One®, Watkins®, Hot Spring®, Tiger River®, Caldera®, or Solana®. All brand names are used solely for compatibility and identification purposes.

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