🛁 Little Giant S320PT-20 Stainless Steel & Bronze Circulation Pump – 115V 335 GPH

Corrosion-proof stainless steel and bronze construction for saltwater, freshwater, and hot water applications

🔄 Product Overview

The Little Giant S320PT-20 (517100001) is a premium stainless steel and bronze direct drive circulation pump manufactured by Franklin Electric under the Little Giant brand. Designed for continuous duty operation, this pump delivers up to 335 GPH (approximately 5.6 GPM) at 1-foot lift while consuming just 0.50A and 60W at 115V — making it one of the most energy-efficient circulation pump options available.

What sets this pump apart from conventional spa circulation pumps is its stainless steel case with bronze pump body and corrosion-proof fasteners, engineered to operate in freshwater, saltwater, chlorinated water, and brominated water environments. The pump is rated for hot water applications up to 110°F (43°C) and features an oil-less PSC (Permanent Split Capacitor) motor that is safe for fish and aquatic life — meaning zero oil contamination risk in your spa water.

The S320PT-20 can be used submersed or inline (not self-priming — must be installed below water level). It comes equipped with a 20-foot power cord with 3-prong plug, a built-in flow control valve for adjusting water output, and an included inlet prefilter screen for debris protection. With 1/2″ MNPT intake and 1/4″ MNPT discharge threaded connections, this pump provides a compact, corrosion-resistant circulation solution. This pump is the manufacturer replacement for the discontinued Cal Pump S320-20.

✨ Key Features

• ✅ Stainless Steel & Bronze Construction — Stainless steel case, bronze pump body, and corrosion-proof fasteners for maximum durability in any water chemistry
• ✅ 115V / 0.50A / 60W — Ultra-low energy consumption for continuous 24/7 circulation at pennies per day
• ✅ 335 GPH at 1 ft Lift — Approximately 5.6 GPM flow rate with 14.8 ft maximum shutoff head
• ✅ Oil-Less PSC Motor — Permanent Split Capacitor continuous duty motor with no oil contamination risk, safe for aquatic environments
• ✅ Submersible or Inline Operation — Versatile installation options to match your equipment configuration
• ✅ Built-In Flow Control Valve — Adjust water output to match your circulation requirements without external valves
• ✅ Inlet Prefilter Screen INCLUDED — Removable debris protection for submersed operation, or remove for inline use
• ✅ 20-Foot Power Cord with 3-Prong Plug INCLUDED — Extra-long cord for flexible placement, ready to plug in
• ✅ Saltwater, Freshwater, Chlorinated & Brominated Compatible — Operates in all common spa water chemistries
• ✅ Hot Water Rated to 110°F (43°C) — Designed for hot water spa and hot tub circulation applications
• ✅ Thermally Protected — Built-in thermal overload protection prevents motor damage from overheating
• ✅ 2-Year Limited Manufacturer Warranty — Coverage from Franklin Electric / Little Giant

🔩 Technical specifications

⚡ Electrical Requirements

⚠️ IMPORTANT:

All electrical work must be performed by a licensed electrician in accordance with the National Electrical Code (NEC) and local building codes. Hot tubs require GFCI (Ground Fault Circuit Interrupter) protection. A dedicated circuit is required — do not share with other appliances.

⚠️ CRITICAL — 115V ONLY:

This pump operates on 115V / 60Hz only. Verify your spa’s electrical supply before ordering. The 20-foot cord with 3-prong plug allows direct connection to a GFCI-protected outlet or hardwiring to a spa control system (plug may be removed for hardwiring if required by your spa configuration).

🔗 Compatibility Guide

Little Giant S-Series Stainless Steel & Bronze Family

Model	Flow Rate	Connections	Cord	Part Number
S320PT-20 (This Pump)	335 GPH	1/4″ × 1/2″ MNPT	20 ft	517100001
S580PT-20	740 GPH	1/2″ × 3/4″ MNPT	20 ft	See Manufacturer
S900PT-20	795 GPH	1/2″ × 3/4″ MNPT	20 ft	See Manufacturer
S1200PT-20	920 GPH	1/2″ × 3/4″ MNPT	20 ft	See Manufacturer

Replaces Cal Pump / Calvert Engineering Models

The Little Giant S320PT-20 is the manufacturer-designated replacement for the following discontinued Cal Pump / Calvert Engineering models:

Discontinued Model	Description	Replaced By
S320-20	Cal Pump 320 GPH, 20 ft Cord, 1/2″ × 1/4″ MNPT	S320PT-20 (517100001)
S320T-20	Cal Pump / Calvert S320, 20 ft Cord	S320PT-20 (517100001)
S320T-6	Cal Pump 320 GPH, 6 ft Cord, 1/2″ × 1/4″ MNPT	S320PT-20 (517100001) — Note: Cord length difference

Connection Notes

This pump uses MNPT (Male National Pipe Thread) threaded connections — NOT barb or union connections found on typical spa circulation pumps:

• 📍 Intake: 1/2″ MNPT — accepts 1/2″ FNPT fittings
• 📍 Discharge: 1/4″ MNPT — accepts 1/4″ FNPT fittings
• 📍 Flow Control: Built-in adjustable valve at discharge port

⚠️ These are smaller threaded connections compared to standard spa circulation pumps (which typically use 3/4″ or 1″ barb connections). Verify your spa’s plumbing configuration before ordering. Appropriate MNPT-to-barb or MNPT-to-slip adapters may be required for your installation.

Hot Water Application Note

This pump is rated for hot water up to 110°F (43°C). Most hot tubs operate at a maximum set temperature of 104°F (40°C), which is within this pump’s operating range. However, water temperatures in the equipment bay near heater output can occasionally exceed the set temperature. Ensure the pump is installed in a location where water temperature will not exceed 110°F.

🔩 Alternate Part Numbers & Cross-References

🔧 Parts and fittings for this

Primary Part Numbers

Part Number	Description
517100001	Little Giant / Franklin Electric — Current Part Number
S320PT-20	Little Giant Model Name
S320T-20	Alternate Model Reference
517003	Former Little Giant Part Number (Replaced by 517100001)

Cal Pump / Calvert Engineering (Discontinued — Replaced by 517100001)

Part Number	Description
S320-20	Cal Pump — 320 GPH, 20 ft Cord (DISCONTINUED)
S320T-20	Calvert Engineering — 320 GPH, 20 ft Cord (DISCONTINUED)
S320T-6	Cal Pump — 320 GPH, 6 ft Cord (DISCONTINUED)

Replacement Parts

Part Number	Description
305626001	Repair Kit for S320PT-20 (517100001)

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🛠️ Installation Requirements

What’s in the Box

• ✅ Little Giant S320PT-20 Stainless Steel & Bronze Pump
• ✅ 20-Foot Power Cord with 3-Prong Plug
• ✅ Removable Inlet Prefilter Screen
• ✅ Built-In Flow Control Valve

Mounting — Submersible Installation

Requirement	Specification
Position	Fully submerged in water
Prefilter	Attach included prefilter screen to intake
Flow Control	Adjust built-in valve to desired flow rate
Temperature	Water must not exceed 110°F (43°C)

Mounting — Inline Installation

Requirement	Specification
Position	Below water level (NOT self-priming)
Prefilter	Remove prefilter screen for inline use
Connections	1/2″ FNPT fittings on intake, 1/4″ FNPT fittings on discharge
Flow Control	Adjust built-in valve to desired flow rate
Temperature	Water must not exceed 110°F (43°C)

Installation Notes

⚠️ This pump is NOT self-priming. It must be installed below the water level at all times for proper operation.

⚠️ Maximum water temperature is 110°F (43°C). Do not install in locations where water temperature may exceed this limit, such as directly at heater output.

⚠️ The built-in flow control valve allows adjustment of water output — turn to increase or decrease flow without external valves.

⚠️ For submersed use, attach the included prefilter screen to the intake to protect the pump from debris. For inline use, the prefilter may be removed.

⚠️ Connections are 1/2″ MNPT intake and 1/4″ MNPT discharge. These are smaller than standard spa circulation pump connections — adapters may be required.

⚠️ GFCI protection is required by the National Electrical Code (NEC) for all hot tub and spa installations.

⚠️ The 20-foot cord provides flexibility in pump placement. Route cord safely away from heat sources and moving parts.

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🔧 Maintenance Guide

Routine Maintenance

Task	Frequency	Notes
Check prefilter screen	Weekly (if submersed)	Clean debris from inlet screen
Inspect for leaks	Monthly	Check threaded connections
Verify flow rate	Monthly	Reduced flow indicates clogging
Inspect power cord	Quarterly	Check for damage, especially near water
Clean pump exterior	Quarterly	Remove mineral buildup from stainless steel
Check flow control valve	Quarterly	Ensure smooth operation

Warning Signs — Replace Pump If:

• Unusual noise (grinding, humming, rattling)
• Motor overheating beyond thermal protection cycling
• Reduced or no water flow despite clean intake
• Visible corrosion on stainless steel or bronze components
• Water leaking from pump body
• Motor fails to start or trips breaker repeatedly

Repair Kit Available

A factory repair kit is available for this pump:

• 📍 Part Number: 305626001
• 📍 For Pump: 517100001 (S320PT-20)
• 📍 Order from Parts4Tubs or authorized Little Giant dealers

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🎯 Ideal Applications

Application	Suitability	Notes
♨️ Spa / Hot Tub Circulation	✅ Yes	Rated for hot water up to 110°F — verify spa max temp
♨️ Saltwater Spa Systems	✅ Yes	Stainless steel and bronze resist salt corrosion
♨️ Chlorinated / Brominated Water	✅ Yes	Compatible with all common spa sanitizers
♨️ Replacement Cal Pump S320-20	✅ Yes — Direct Replacement	Manufacturer-designated replacement
♨️ Submersible Circulation	✅ Yes	Install in skimmer or equipment well
♨️ Inline Circulation	✅ Yes	Must be below water level (not self-priming)
💧 Pond / Water Feature	✅ Yes	Primary design application
💧 Fountain / Water Display	✅ Yes	Primary design application
🛁 1″ Barb Spa Plumbing	⚠️ Adapters Required	Uses 1/2″ and 1/4″ MNPT — not barb connections
🛁 High-Flow 10+ GPM	❌ No	Max 335 GPH (5.6 GPM) — consider Laing E-10 or Grundfos
🛁 Water Over 110°F	❌ No	Maximum operating temperature is 110°F

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❓ Frequently Asked Questions

Q: What is the flow rate of this pump? A: 335 GPH (approximately 5.6 GPM) at 1-foot lift, with a maximum shutoff head of 14.8 feet. The built-in flow control valve allows you to adjust output as needed.

Q: What are the connection sizes? A: 1/2″ MNPT (Male National Pipe Thread) intake and 1/4″ MNPT discharge. These are threaded connections, not barb or union. Appropriate adapters may be needed for your spa’s plumbing.

Q: Can this pump be used in a hot tub? A: Yes. The S320PT-20 is rated for hot water applications up to 110°F (43°C), which is within normal hot tub operating range (typically 100-104°F). It operates in saltwater, chlorinated, and brominated water. Verify that water temperature in your pump’s installation location does not exceed 110°F.

Q: Does this pump come with a power cord? A: Yes. A 20-foot power cord with 3-prong plug is included — significantly longer than most spa circulation pump cords, providing excellent placement flexibility.

Q: Can this pump be submerged? A: Yes. The S320PT-20 can be used fully submerged or installed inline below water level. When submerged, attach the included prefilter screen to protect the intake from debris.

Q: Is this pump self-priming? A: No. This pump must be installed below the water level at all times. It cannot draw water up from below — it requires flooded suction.

Q: What does this pump replace? A: The Little Giant 517100001 is the manufacturer-designated replacement for the discontinued Cal Pump / Calvert Engineering S320-20, S320T-20, and S320T-6 models.

Q: What is the flow control valve? A: A built-in adjustable valve located at the discharge port that lets you increase or decrease water flow without installing external valves or plumbing modifications.

Q: Is the motor oil-free? A: Yes. The PSC (Permanent Split Capacitor) motor is completely oil-less, meaning there is zero risk of oil contamination in your spa water. This design is safe for fish and aquatic life.

Q: What is the stainless steel and bronze construction for? A: The stainless steel case, bronze pump body, and corrosion-proof fasteners provide superior resistance to corrosion from saltwater, chlorine, bromine, and mild acids — far exceeding the durability of typical thermoplastic pump housings in aggressive water chemistries.

Q: What warranty is included? A: 2-year limited manufacturer warranty from Franklin Electric / Little Giant. Contact Parts4Tubs for full warranty terms and support.

Q: Is there a repair kit available? A: Yes. Little Giant offers repair kit part number 305626001 specifically for the S320PT-20 (517100001).

Q: Do I need a GFCI breaker? A: Yes. GFCI protection is required by the National Electrical Code (NEC) for all hot tub and spa installations.

🏆 Why Choose the Little Giant S320PT-20

• ✅ Stainless Steel & Bronze Construction — Premium corrosion-resistant materials far exceed standard thermoplastic pump housings
• ✅ Saltwater, Chlorine & Bromine Compatible — Operates in all common spa water chemistries without degradation
• ✅ Oil-Less PSC Motor — Zero contamination risk with continuous duty design and built-in thermal protection
• ✅ Built-In Flow Control Valve — Adjust circulation flow without additional plumbing modifications
• ✅ 20-Foot Power Cord with Plug INCLUDED — Extra-long cord provides maximum installation flexibility, ready to plug in
• ✅ Submersible or Inline — Versatile mounting options to match any equipment configuration
• ✅ Ultra-Low Energy — Just 0.50A and 60W for continuous 24/7 operation at pennies per day
• ✅ Compact & Lightweight — 5.25″ L × 4.5″ diameter fits tight equipment compartments
• ✅ Included Prefilter Screen — Protects pump from debris in submersed applications
• ✅ Direct Cal Pump S320-20 Replacement — Manufacturer-designated successor from the same parent company (Franklin Electric)
• ✅ Repair Kit Available — Part 305626001 extends pump life at low cost
• ✅ 2-Year Limited Manufacturer Warranty — Backed by Franklin Electric, a global leader in water systems

🤝 Why Buy from Parts4Tubs

• ✅ US-based support for American customers
• ✅ Fast shipping across the United States
• ✅ Expert advice from spa and hot tub specialists
• ✅ Competitive pricing in USD
• ✅ Full warranty support
• ✅ Hassle-free returns
• ✅ Replacement parts and repair kits available
• ✅ Dedicated customer service team

✨ Summary

The Little Giant S320PT-20 (517100001) is a premium stainless steel and bronze circulation pump delivering 335 GPH at just 0.50A and 60W on 115V. Featuring corrosion-proof construction for saltwater, chlorinated, and brominated water, an oil-less PSC motor with thermal protection, built-in flow control valve, included prefilter screen, and a 20-foot power cord with plug, this pump provides versatile submersible or inline operation for hot water applications up to 110°F. The manufacturer-designated replacement for the discontinued Cal Pump S320-20. Order from Parts4Tubs today with 2-year warranty support.

Unions and pump cords: pick the union size that matches your pump's ports (see the size chart below), and a 4-wire cord for a 2-speed pump.

How do I Replace a Hot Tub Pump?

Here's a general step-by-step guide on how to replace a hot tub pump. Keep in mind that the specific steps may vary depending on your hot tub's make and model, so it's essential to consult your hot tub's manual for model-specific instructions. If you're not comfortable with this procedure, it's a good idea to seek professional assistance.

Materials You'll Need:

• Replacement pump
• Screwdriver
• New union O-rings
• A strap wrench, only if a union nut is stuck
• PVC primer and cement, only if you are gluing in new tailpieces

Procedure:

1. Turn Off the Power: Before you begin, ensure the hot tub's power supply is turned off at the circuit breaker or disconnect switch. Safety should always be a priority when working with electrical components.

2. Drain the Hot Tub: If your hot tub is not already empty, you'll need to drain it. Follow your hot tub's manual or manufacturer's instructions for proper draining. (You might not need to do this if you can lock the pump off with the gate valves)

3. Locate the Pump: Identify the location of the existing pump in your hot tub. It's usually located near the equipment area or in a designated pump compartment.

4. Disconnect the Electrical Wiring: Carefully disconnect the electrical wiring from the old pump. This typically involves removing the electrical conduit cover, unscrewing wire nuts, and disconnecting the wires from the terminals. Be sure to note the wire connections or take a picture for reference when connecting the new pump.

5. Disconnect the Plumbing: Depending on your hot tub's plumbing setup, you'll need to disconnect the plumbing connections to the pump. Unscrew the union nuts by hand. If one is stuck, use a strap wrench rather than a pipe wrench, which can crack the nut. Be prepared for some water spillage when disconnecting the plumbing.

6. Remove the Old Pump: Once the electrical and plumbing connections are detached, carefully remove the old pump from its mounting position. Some pumps may be secured with mounting brackets or bolts.

7. Prepare the New Pump: If the new pump is not pre-assembled, you may need to attach fittings, unions, or adapters to match your hot tub's plumbing. Pump unions use buttress threads that seal on an O-ring, so fit new O-rings and hand-tighten the nuts. Do not use thread tape, pipe dope or sealant on them.

8. Mount the New Pump: Position the new pump in the same location as the old one and secure it in place using the mounting brackets or bolts.

9. Reconnect Plumbing: Reconnect the plumbing to the new pump, hand-tightening the union nuts. If you are gluing in new PVC tailpieces, use PVC primer and cement on those joints.

10. Reconnect Electrical Wiring: Reconnect the electrical wiring to the new pump, following the notes or pictures you took earlier. Make sure all wires are properly connected and secure.

11. Turn On the Power: Restore power to the hot tub by switching on the circuit breaker or reconnecting the disconnect switch.

12. Test the Pump: Turn on the hot tub's pump to ensure that it's working correctly. Check for any signs of leaks or irregularities in the plumbing connections.

13. Refill the Hot Tub: Once you've confirmed that the new pump is functioning properly, refill the hot tub with water.

14. Check for Leaks: Inspect the plumbing connections for any leaks. If you find any, turn off the pump, drain the tub again, and reseal the connections as needed.

15. Monitor: Keep an eye on the pump and plumbing for the next few days to ensure everything is functioning correctly and that there are no further issues.

Remember that this is a general guideline, and the specific steps may vary based on your hot tub's design. If you're unsure or uncomfortable with any aspect of this process, please do get in touch, happy to help.

How do I know what size hot tub pump I have?

Determining the size of your hot tub pump is an important step when it comes to maintenance or replacement. To find out the size of your hot tub pump, follow these steps:

1. Check the Manual: The easiest way to determine the size of your hot tub pump is to consult the owner's manual or user documentation that came with your hot tub. The manual typically contains detailed information about the specifications and components of your hot tub, including the pump.

2. Look at the Pump Housing: If you don't have access to the manual or it doesn't provide the information you need, inspect the pump itself. Most hot tub pumps have a label or plate on the pump housing that displays essential details, including the pump's model number, manufacturer, and specifications. You can then send that to me or Google it.

3. Measure the Pump: If the label is missing or damaged, you can measure the pump's dimensions. Measure the diameter of the pump's wet end (the part where the water flows) and the length of the wet end. These measurements can help identify the size and capacity of the pump.

4. Consult the Manufacturer: If you can't find the information on the pump or in the manual, contact the hot tub manufacturer or a reputable dealer. Provide them with your hot tub's model and serial number, and they should be able to identify the correct pump size for your specific hot tub.

5. Online Research: You can also search online using the pump's model number or hot tub's make and model. Many manufacturers provide detailed information about their products on their websites, and you may find specifications for your pump model.

Once you have determined the size and specifications of your hot tub pump, you can proceed with maintenance, repairs, or replacement if necessary. Keep in mind that replacing a hot tub pump with the same size and capacity as the original is crucial to ensure proper water circulation and filtration in your hot tub. If you're unsure about any aspect of this process, get in touch, always happy to help.