Grundfos · Submersible Pump End
77S SP 4 in Pump End
77 GPM class stainless steel SP pump end, motor not included: 14 builds for 3/4 to 10 HP motors, on 4 in and 6 in motors.
77 GPM Rated Flow
3/4-10 HP
37-396 ft Nominal Head
2 in NPT Discharge
4 in and 6 in Motor Fit
NEMA Motor Flange
Built-In Check Valve
AISI 304 Stainless Steel
cCSAus
11.0-46.1 lb Weight
What Ships and What It Needs to Run
Included: the Grundfos 77S SP pump end with its built-in check valve.
Submersible motor required, ordered separately. The pump end mounts on a 4 in or 6 in submersible motor with a NEMA motor flange, plus the motor’s control: a control box for a single-phase 3-wire motor, or a starter or drive for a three-phase motor. The motor horsepower and diameter for each build are in the Models & Ratings table.
Overview
The Grundfos 77S is the 77 GPM class of the SP 4 in submersible range, sold here as the pump end alone: stainless steel chambers and impellers with a built-in check valve, ready to mount on a submersible motor. Pump and impellers are AISI 304 stainless steel. Use it to rebuild an SP installation on a sound motor, or to build a pump around a motor you already have; the complete 77S pump with a Grundfos motor is listed separately.
The 77S pump end has a NEMA motor flange. Match the motor horsepower and diameter in the selector, and the flange to your motor; send us the motor model and we will confirm the fit.
Genuine Grundfos equipment, factory-new in original packaging — sold and supported by Watermain Supply, an independent industrial supplier.
Warranty
24 months from date of installation, but not more than 30 months from date of manufacture. In Grundfos's words, products are “warranted to the original user only to be free of defects in material and workmanship”; the full terms are in the installation and operating instructions on the Data Sheet tab.
Single Pump or a Set?
Each pump end builds one pump for one well. For a duty/standby pair, or a flow outside the 77S range, send us the duty: the other SP 4 in flow classes run from 5 to 77 GPM, and we will size the set with you.
Check the Part Number
The model code reads flow class, horsepower and stages: 77S75-15 is the 77S for a 7-1/2 HP motor with 15 stages. In the selector, choose the motor horsepower and diameter first, then the model; each model shows the head it adds at 77 GPM. Order by part number; every build is in the Models & Ratings table.
- Some models come in a 4 in motor build and a 6 in motor build under different part numbers; the selector shows the motor size with the horsepower.
Models & Ratings
| Model |
Part No. |
Motor HP |
Motor |
Discharge |
Min. Well |
Nominal Head at 77 GPM, ft |
Net Weight, lb |
| 77S7-2 |
98914844 |
3/4 |
4 in |
2 in NPT female |
4 in |
37-38 |
11.0 |
| 77S15-3 |
98924090 |
1-1/2 |
4 in |
2 in NPT female |
4 in |
60-61 |
12.8 |
| 77S20-4 |
98924091 |
2 |
4 in |
2 in NPT female |
4 in |
77 |
14.6 |
| 77S30-6 |
98924092 |
3 |
4 in |
2 in NPT female |
4 in |
113-117 |
18.1 |
| 77S50-8 |
98924093 |
5 |
4 in |
2 in NPT female |
4 in |
157-159 |
21.6 |
| 77S50-10 |
98924094 |
5 |
4 in |
2 in NPT female |
4 in |
192-195 |
25.1 |
| 77S75-12 |
98924095 |
7-1/2 |
4 in |
2 in NPT female |
4 in |
237 |
28.7 |
| 77S75-15 |
98924096 |
7-1/2 |
4 in |
2 in NPT female |
4 in |
293 |
34.0 |
| 77S75-12 |
98924099 |
7-1/2 |
6 in |
2 in NPT female |
6 in |
239-240 |
32.0 |
| 77S75-15 |
98924100 |
7-1/2 |
6 in |
2 in NPT female |
6 in |
295-297 |
37.3 |
| 77S100-17 |
98924097 |
10 |
4 in |
2 in NPT female |
4 in |
337 |
37.5 |
| 77S100-20 |
98924098 |
10 |
4 in |
2 in NPT female |
4 in |
392 |
42.8 |
| 77S100-17 |
98924101 |
10 |
6 in |
2 in NPT female |
6 in |
337-340 |
40.8 |
| 77S100-20 |
98924102 |
10 |
6 in |
2 in NPT female |
6 in |
393-396 |
46.1 |
Part numbers, horsepower, motor size and minimum well: Grundfos US price list, effective January 1, 2026. Nominal head: Grundfos SP data booklet, 60 Hz, May 2026 (complete-pump tables for the same model and motor size; where two figures are shown, builds on different motors or voltages differ slightly). Discharge thread and net weight of the pump end: Grundfos Product Center.
Shared Specifications
| Specification |
Value |
| Rated flow |
77 GPM |
| Motor horsepower |
3/4 to 10 HP |
| Motor |
4 in or 6 in submersible motor, NEMA motor flange |
| Discharge |
2 in NPT |
| Minimum well |
4 / 6 in (per build, Models & Ratings table) |
| Check valve |
Built in |
| Liquid temperature |
Up to 140°F (60°C) at the pump end; the motor sets the working limit |
| Approvals |
cCSAus and CULDWUS (Grundfos Product Center codes) |
| Curve tolerance |
ISO 9906 |
| Included |
Pump end only; motor and its control ordered separately |
Performance — Will It Do What You Need?
Every 77S is rated at 77 GPM. The nominal head in the Models & Ratings table is the total head Grundfos publishes for each model at that rated flow, in feet. Pick a model whose nominal head covers your pumping level plus the pressure you need at the surface (2.31 ft per psi) plus pipe friction.
Source: Grundfos SP data booklet, 60 Hz, May 2026 (SP 77S tables, pages 61-64). Performance conforms to ISO 9906. The 77S head and power curves are in the product images, and the 77S data sheet on the Data Sheet tab carries the full curves and tables.
Before You Buy — The Limits That Decide the Fit
| Check |
What to confirm |
| Motor |
A 4 in or 6 in submersible motor of the horsepower in the selector, with a NEMA motor flange; ordered separately |
| Motor control |
Control box for a single-phase 3-wire motor; starter or drive for a three-phase motor |
| Well size |
Casing ID at least the minimum well for the build (Models & Ratings table) |
| Duty point |
Choose the model from the Grundfos curve at your flow and total head. Send us the pumping level, pipe run and pressure and we will check it against the curve |
Materials of Construction
| Part |
Material |
| Pump |
Stainless steel, EN 1.4301 (AISI 304) |
| Impellers |
Stainless steel, EN 1.4301 (AISI 304) |
Source: Grundfos Product Center.
