What Size Well Pump Do I Need?
A Goulds well pump sizing chart does not start with horsepower. It starts with two numbers you can measure: how many gallons per minute the house actually needs, and how many feet of total dynamic head (TDH) the pump has to produce to put that water into a 30-50 PSI tank. Shop 1 HP because the last pump was 1 HP and you will either short the second shower or bury a motor that never leaves the left side of its curve.
This is the same path we walk on a Home, Well and Septic sizing call. Goulds Water Technology publishes the residential peak-demand table and the 10GS depth-to-water chart we use below. We stock Goulds equipment, jet pumps, and 4-inch submersibles. Goulds GS water ends and J+ jets are selected from the current literature. If the exact water end is not on a product page yet, send the duty and we will quote the matching Goulds model.
US homeowners, well drillers, and contractors: treat every GPM and PSI figure in this guide as chart math, not a promise for your well. Well yield, drawdown, and wire size still have to match the pump. If the well makes 6 GPM, a 14 GPM pump will not invent the other 8.
Get the GPM Demand
Count fixtures (1 GPM each) or use the Goulds seven-minute bathroom table. Add hose bibs and irrigation if they run with the house.
Build the Well TDH
Pumping level plus vertical lift, 50 PSI tank cut-out times 2.31, plus friction. That is the duty the chart has to hit.
Read the Sizing Chart
Pick jet or submersible from well depth, then land on a Goulds 10GS (or J+) cell at your PSI and depth. Horsepower is the leftover.
Start here when you already know it is a drilled well and you need pumps tagged for well duty, not sump or sewage.
Watch for: The Wells node is an application filter, not a Goulds series page.
Published shallow-well jets on this site, including STA-RITE HN, CJ, FL, and HL series we use when a Goulds J+ is not on the shelf.
Watch for: Practical suction lift is about 25 ft at sea level. Deeper than that is a deep-well jet or a submersible.
Submersible type node. For well-only catalogs see Myers Predator Plus, Myers Ranger, Shakti, and Flotec.
Watch for: This type tree also holds sewage and dewatering submersibles. Stay on a well series.
Calculate GPM Demand (Fixture Count and Peak Use)
Goulds Water Technology's Water Products technical manual (TTECHWP R7, page 6) gives two residential methods. Use both. If they disagree, take the higher number and ask whether irrigation or a hose bib runs during the morning peak.
Fixture-count method
The same Goulds page says: count every fixture in the home, including outside hose bibs, and supply one gallon per minute each. A two-bath house with a kitchen sink, dishwasher, washer, laundry tub, and two hose bibs is 12 fixtures, so 12 GPM. That is the Goulds fixture-count rule from TTECHWP, not a plumbing-code fixture-unit conversion.
GPM_fixtures = number of fixtures (including hose bibs) x 1 GPM each | Example: 2 baths (6 outlets) + kitchen + dishwasher + washer + laundry tub + 2 hose bibs = 12 GPM
Seven-minute peak-demand method
Goulds also publishes a seven-minute peak table for private residences. Peak demand shows up in the morning and evening. Seven minutes is their stated high-use window for a shower or washer. The table below is copied from TTECHWP R7 page 6 (same numbers appear in the parallel TTECHWP technical-manual PDF). Values are averages. They do not include irrigation, livestock, or a pool fill.
1 bathroom
Peak gallons: 45
Min GPM: 7 GPM
GPH: 420 GPH
1.5 bathrooms
Peak gallons: 70
Min GPM: 10 GPM
GPH: 600 GPH
2 to 2.5 bathrooms
Peak gallons: 98
Min GPM: 14 GPM
GPH: 840 GPH
3 to 4 bathrooms
Peak gallons: 122
Min GPM: 17 GPM
GPH: 1020 GPH
Source: Goulds Water Technology TTECHWP R7, Jet and Submersible Pump Selection, Private Residences. Dual-checked against the TTECHWP technical-manual PDF. Add yard fixtures separately: 1/2 in garden hose 3 GPM, 3/4 in garden hose 6 GPM, lawn sprinkler 3 to 7 GPM (same page).
Worked house we will carry through the chart
Two bathrooms, no irrigation during the morning peak. Goulds seven-minute table: 14 GPM. Fixture count on the same house is often 10 to 12 GPM. We will size the chart example at 14 GPM so the tank can refill while two fixtures run.
Do not confuse this with well yield. The pump GPM must be at or below what the well can give at the pumping level you used for TDH. If the well is weak, you need storage (a larger tank or a cistern) or a low-yield control, not a bigger impeller stack.
Calculate TDH for a Well (Lift, Tank PSI, Friction)
Goulds defines total dynamic head as dynamic discharge head plus dynamic suction lift, or minus dynamic suction head (TTECHWP R7, Terms and Usable Formulas). On a well you almost always have lift, not suction head. For a submersible the pump sits below the water, so the lift you care about is the pumping level: the vertical distance from the pumping water surface up to the wellhead, plus any rise from the wellhead to the pressure tank.
Pumping level, not static level
Static level is where the water sits with the pump off. Pumping level is where it sits after drawdown. Goulds shows an air-line method: length of tube minus (gauge PSI x 2.31). Example in TTECHWP: 100 ft tube, 20 PSI on the gauge, depth to water = 100 - 46.2 = 53.8 ft.
Size at tank cut-out, not cut-in
A Goulds J+ ships with an AS4 switch preset at 30-50 PSI (BJ+ R5). The chart cell that matters is the 50 PSI row. If the pump cannot make 50 PSI at your depth, the tank never fills and the motor never shuts off.
Friction is extra feet of lift
TTECHWP SCH 40 plastic, 10 GPM: 1-1/4 in pipe = 1.78 ft per 100 ft, 1-1/2 in = 0.83 ft per 100 ft. At 15 GPM, 1-1/4 in rises to 3.75 ft per 100 ft. Add fittings (a 1-1/4 in swing check is 9 ft of equivalent pipe on the fittings table in the same manual).
Elevation after the wellhead
If the tank sits 8 ft above the well cap, that 8 ft is static discharge head. Add it. Goulds depth-to-water charts assume you have already rolled extra elevation and friction into the depth you look up, or that they are small next to the 20 ft column steps.
H_pressure (ft) = 2.31 x tank cut-out PSI (Goulds TTECHWP: H = 2.31 x psi / Sp.Gr.) | TDH (ft) = pumping level + wellhead-to-tank rise + H_pressure + friction head | Chart depth to use at 50 PSI = TDH - (50 x 2.31) | Worked: 100 ft pumping level + 0 ft rise + (50 x 2.31 = 115.5) + 4.5 ft friction = 220 ft TDH | Equivalent chart depth at 50 PSI = 220 - 115.5 = 104.5 ft (read the 100 ft column)
Friction in that example: 120 ft of 1-1/4 in SCH 40 plastic at about 14 GPM. Goulds lists 3.75 ft per 100 ft at 15 GPM, so 3.75 x 1.2 = 4.5 ft. That is inside the 20 ft column spacing on the 10GS chart, so the 100 ft column is the right cell.
Jet pumps use suction lift, not the same TDH worksheet
Goulds' rule of thumb for a shallow-well jet: practical suction lift at sea level is 25 ft. Deduct 1 ft of suction lift per 1,000 ft of elevation (TTECHWP, Calculating Suction Lift). A deep-well jet moves the jet assembly at least 5 ft below the low water. Read the J+ twin-pipe or packer table as depth to the jet, not as submersible TDH.
Jet vs Submersible: Shallow Well or Deep Well
Goulds splits jet pumps by where the jet assembly lives (TTECHWP, Pump Fundamentals). A shallow-well jet keeps the nozzle and venturi at the pump. One suction pipe goes into the well. A deep-well jet drops the jet assembly into the well so atmospheric pressure only has to lift water a few feet into that assembly. A submersible puts the whole pump and motor under water. No prime, no suction lift limit.
Shallow well (jet on the surface)
Use a jet when pumping level stays within about 25 ft of the pump at sea level (Goulds TTECHWP). Goulds J+ convertible jets (BJ+ R5, October 2024) are 1/2, 3/4, 1, and 1-1/2 HP (J5, J7, J10, J15), 3500 RPM, 115/230 V, 1-1/4 in suction and 1 in discharge, 140 F maximum. Shallow-well J15 at 25 ft suction and 50 PSI is 14.0 GPM on that brochure. Live shallow-well jets on this site include STA-RITE HN (HNC 1/2 HP, 5HNE 1 HP) and STA-RITE CJ (CJ90F).
J+ figures: BJ+ R5 only (site library PDF). 25 ft lift: TTECHWP plus the J+ shallow-well table, which stops at 25 ft.
Deep well (submersible in the casing)
Once the pumping level is past jet range, a 4-inch submersible is the default. Goulds 10GS water ends (B5-25GS R9) are built for 4 in and larger wells, 1-1/4 in NPT discharge, 3 to 16 GPM recommended range, 10 GPM best efficiency, 1/2 to 5 HP, 3450 RPM, 60 Hz. The same 14 GPM / 50 PSI duty at 100 ft pumping level lands on 10GS15 at 14.0 GPM. Deep-well jets still exist (J+ twin-pipe tables go to about 90 to 150 ft depending on HP and jet package) but capacity falls fast. For published 4 in well pumps see Myers Predator Plus ST and Myers Ranger.
10GS range and BEP: B5-25GS R9 and R8. 10GS15 50 PSI / 100 ft = 14.0 GPM on both revisions.
Convertible jets (Goulds J+, STA-RITE HL, STA-RITE FL including FLC at 1/2 HP) can run shallow or deep if you change the adapter and jet package. Deep-well J+ needs a JDW fittings package or AV22 kit and a pressure-control valve. BJ+ R5 is blunt: fail to set the back pressure and the pump loses prime.
Pick jet or submersible in one pass
If two of the submersible reasons are true, stop shopping jets.
How to Read a Goulds Well Pump Sizing Chart
Open Goulds brochure B5-25GS R9 (July 2023), model 10GS selection chart. The grid is depth to water across the top (20, 40, 60, 80, 100 ft, and up) and discharge PSI down the side (0, 20, 30, 40, 50, 60). Each cell is GPM. This is the chart people mean when they search "goulds well pump sizing chart" or "submersible well pump chart."
Walk the two-bath house. Demand is 14 GPM. Pumping level is 100 ft. Tank is 30-50 PSI, so read the 50 PSI row. Friction and rise folded in as above, so the 100 ft column is the lookup.
10GS07 (HH after 8/2017)
HP: 3/4
GPM at 100 ft: 11.5
Fit: Short. Two fixtures will starve.
10GS10 (HH after 8/2017)
HP: 1
GPM at 100 ft: 13.3
Fit: Close, still under 14 GPM.
10GS15
HP: 1-1/2
GPM at 100 ft: 14.0
Fit: Hits 14 GPM on the cell.
10GS20
HP: 2
GPM at 100 ft: 14.6
Fit: Extra margin if friction was understated.
GPM cells from B5-25GS R9, Model 10GS selection chart, 50 PSI row. Dual-checked on B5-25GS R8 (same 10GS15 50 PSI / 100 ft = 14.0). 10GS05 through 10GS10 are the high-head hydraulics Goulds marked with an asterisk for units built starting August 2017.
Same house, 25 ft dug well, surface jet: BJ+ R5 shallow-well table, 25 ft suction, 50 PSI. J10 makes 10.4 GPM. J15 makes 14.0 GPM. That is why a 1-1/2 HP jet and a 1-1/2 HP 10GS can be the right answer for the same GPM and a completely different well. The jet is fighting suction lift. The submersible is fighting 100 ft of water column plus 50 PSI.
Stay inside the recommended GPM band
B5-25GS R9 prints a recommended range on every curve. 10GS is 3 to 16 GPM with best efficiency at 10 GPM. Our 14 GPM duty is on the right half of that band, still inside the published window. Do not pick an 18GS (6 to 28 GPM, BEP 18) just because 18 is bigger than 14. You will run left of BEP, make extra head you have to throttle, and pay for stages you do not use.
High-capacity wells (20 GPM and up) move to 13GS, 18GS, 25GS in the same brochure, or 35GS through 85GS in B35-85GS (2 in discharge, 10 to 120 GPM depending on series). The e-GS Xtreme CBM line (B5-85GSX R6) uses a 2 in discharge and is the deep-set, high-TDH cousin (Goulds states over 1,600 ft TDH on that brochure). Do not mix Xtreme stage counts with B5-25GS water-end lengths.
1/2 to 2 HP Selection Table (Goulds 10GS at 50 PSI)
Most houses land on 1/2 to 2 HP. The table is the Goulds 10GS family (10 GPM best efficiency, 4 in minimum well, 1-1/4 in discharge) at a 50 PSI cut-out, which is the J+ factory switch and the usual residential tank. Read 80 ft if you have a modest drilled well, 160 ft if you do not. Numbers are GPM from B5-25GS R9, confirmed on R8.
10GS05 (HH)
HP: 1/2
Stages: 10 stg, 13.6 in, 8 lb
80 ft: 9.5 GPM
160 ft: 1.0 GPM
Match: 1 to 1.5 bath, shallow pumping level only
10GS07 (HH)
HP: 3/4
Stages: 14 stg, 16.4 in, 9 lb
80 ft: 12.2 GPM
160 ft: 9.6 GPM
Match: 1.5 bath if 160 ft still clears 10 GPM
10GS10 (HH)
HP: 1
Stages: 16 stg, 17.7 in, 11 lb
80 ft: 13.7 GPM
160 ft: 11.5 GPM
Match: 1.5 to 2 bath at moderate depth
10GS15
HP: 1-1/2
Stages: 17 stg, 18.4 in, 12 lb
80 ft: 14.5 GPM
160 ft: 12.3 GPM
Match: 2 to 2.5 bath at 100 ft (14.0 GPM at 100 ft)
10GS20
HP: 2
Stages: 20 stg, 21.7 in, 13 lb
80 ft: 15.0 GPM
160 ft: 13.4 GPM
Match: 2+ bath or extra friction / elevation
Water-end stages, length, and weight: B5-25GS R9 page 2, dual-checked on R8. GPM cells: R9 10GS 50 PSI row; 10GS15 80 ft = 14.5 and 160 ft = 12.3 also match R8. Recommended range remains 3 to 16 GPM. Rotation is CCW from the discharge end. Minimum well size 4 in.
If the house wants 7 GPM, do not stay on 10GS and throttle. Goulds 7GS is 1.5 to 10 GPM with best efficiency at 7 GPM (same brochure). 5GS is 1.2 to 7.5 GPM, BEP 5. 18GS is 6 to 28 GPM, BEP 18, 3/4 to 5 HP. Match the BEP to the duty, then pick HP from the depth column.
We do not currently publish Goulds 10GS15 as a storefront SKU (dev catalog has GS repair parts, not complete water ends). For a pump you can open today in the 1/2 to 1-1/2 HP well-submersible band, use Myers Predator Plus ST or Flotec 4-inch well pumps. For a surface jet analog to J5/J15, use the STA-RITE pages above. Ask us when the chart says Goulds 10GS and you want that exact water end and motor.
Common Well Pump Sizing Mistakes
Shopping by horsepower
1 HP on a 10GS10 at 50 PSI / 100 ft is 13.3 GPM. 1-1/2 HP on a 10GS15 is 14.0 GPM. Same chart family, one cell apart, different bathrooms covered. HP is the motor you attach after the cell is picked, not the search filter.
Using static level instead of pumping level
Drawdown is real. Goulds' air-line example (100 ft tube, 20 PSI, 53.8 ft to water) exists because nobody can see the pumping level from the yard. If you size on static level, the pump runs out of head the first dry August.
Reading the 30 PSI row on a 30-50 tank
Cut-in is 30 PSI. Cut-out is 50 PSI. The pump has to reach cut-out or it never stops. BJ+ R5 presets the J+ switch at 30-50. Read 50 PSI on a Goulds chart unless you are actually setting a 20-40 or 40-60 switch.
Ignoring friction, then blaming the pump
1-1/4 in SCH 40 plastic at 10 GPM is 1.78 ft per 100 ft (TTECHWP). A long offset on a jet is worse: Goulds' offset example adds 24 ft of equivalent lift for 150 ft of 1-1/2 in pair on a 1 HP deep-well jet. Upsizing to 2 in cuts that example to 9 ft.
Oversizing past well yield
A 14 GPM pump on a 6 GPM well will pull the level down to the intake. Goulds discusses tail pipe on weak deep-well jets (34 ft of tail pipe, capacity drops as level falls). On a submersible you need a low-water switch, a cycle sensor, or storage. A bigger GS stack makes the problem faster.
Picking the wrong GS series (BEP miss)
10GS recommended range is 3 to 16 GPM. 25GS is 8 to 33 GPM, BEP 25. Putting a 25GS on a 10 GPM house runs it left of the published band. The motor may still be 1-1/2 HP. The hydraulics are wrong.
Questions We Hear on Well Pump Sizing Calls
What size well pump do I need for a 2 bathroom house?
Goulds TTECHWP R7 says a 2 to 2.5 bath house has a 98-gallon seven-minute peak and needs 14 GPM if you do not rely on tank storage to cover the peak. That is not yet a horsepower. At 50 PSI and 100 ft pumping level, the Goulds 10GS chart (B5-25GS R9) gives 14.0 GPM on a 10GS15 (1-1/2 HP). A 25 ft shallow well at 50 PSI wants a J15 (14.0 GPM on BJ+ R5), not a 10GS.
Where is the Goulds well pump sizing chart?
For 5 to 25 GPM, 1/2 to 5 HP, 4-inch wells: Xylem brochure B5-25GS R9 (July 2023), the per-model selection charts (depth to water vs PSI). For 35 to 85 GPM: B35-85GS. We walk the 10GS chart in this guide. Goulds GS complete pumps are not all on a product tile; start at Goulds Water Technology or contact us with your GPM and TDH.
How do I read a submersible well pump chart?
Find your tank cut-out PSI on the left (use 50 for a 30-50 switch). Find pumping level across the top. The cell is GPM. Stay inside the recommended range printed on that series (10GS: 3 to 16 GPM). If friction or extra elevation is more than about 10 ft, add it to the depth before you pick a column.
Jet pump or submersible for a 100 foot well?
A 100 ft pumping level is past Goulds' 25 ft practical suction lift. A J+ deep-well twin-pipe package can still make water (BJ+ R5 shows J10 packages in the 4 to 8 GPM band at 100 ft, depending on the jet), but you will not hit a 14 GPM two-bath duty. A 4-inch submersible (10GS15 in the worked example) is the honest 14 GPM answer at that depth.
Does well pump horsepower equal GPM?
No. Horsepower is how many stages the motor can turn at your TDH. A 1/2 HP 10GS05 makes 9.5 GPM at 50 PSI / 80 ft and almost nothing at 160 ft (1.0 GPM). A 2 HP 10GS20 still makes 13.4 GPM at 160 ft. Same 10 GPM BEP family, different shut-off head. Always read the cell.
What if my well does not make 14 GPM?
Size the pump at or below well yield at the pumping level, then use tank drawdown for the seven-minute peak. Goulds' bathroom table is house demand, not aquifer capacity. A low-yield well with a 7 GPM 7GS and a larger tank will beat a 14 GPM 10GS that cycles dry. Send the well report if you have one.
Send the well numbers, get a chart pick
We need pumping level (or static plus drawdown), tank switch setting, fixture count or bath count, and casing size. We will read the Goulds 10GS or J+ chart with you and match a published jet or 4-inch submersible if the exact Goulds water end is a quote item.