This is a licensed-professional job
Pulling and rewiring a submersible pump involves 240-volt power, standing water, and an assembly that can weigh several hundred pounds. This guide is written to help you specify and buy intelligently, and to evaluate a contractor's quote — not to help you do the work yourself. Hire a licensed well or pump professional.
Written from field experience: Alabama Grade IV Wastewater Operator. Sizing data sourced from DrillerDB, SC Well Service, CalcEngineer, WellDrillingCosts, McCandless, and BBP Manufacturing — compiled August 2026.
Quick answers
| Question | Short answer |
|---|---|
| What two numbers define a pump? | Required flow in GPM, and total dynamic head in feet. Depth alone does not size a pump. |
| How much flow do I need? | Roughly 1 GPM per water-using fixture. A typical 3-bed, 2-bath home needs about 10–12 GPM. |
| What horsepower? | Falls out of the GPM and TDH calculation, confirmed against a performance curve. Rough guide: ½ HP under 100 ft, ¾–1 HP for 100–300 ft, 1.5–2 HP for 300–500 ft. |
| Submersible or jet? | Submersible for anything deeper than about 25 feet. Pushing water is far more efficient than pulling it. |
| Is a bigger pump better? | No — actively dangerous. An oversized pump can outrun your well's recharge, draw in sand, and burn out running dry. |
| What if my well can't keep up? | Storage, not a bigger pump. A larger pump on a weak well draws it down faster. |
| What will it cost? | National average ~$1,500–$2,827 for replacement, plus ~$500–$1,000 per 100 feet of depth. |
| Biggest avoidable mistake | Letting someone size the pump without measuring your pumping water level and well yield first. |
The one-paragraph version
Count your fixtures to get GPM. Measure your pumping water level and add pressure and friction to get total dynamic head. Check that your required GPM is below your well's sustainable yield. Then find a pump whose published performance curve delivers your GPM at your TDH, inside its efficiency band. Everything else — brand, wire configuration, constant pressure — is a refinement on top of those four steps.
Who this guide is for — six buyer profiles
| Profile | Situation | What usually goes wrong |
|---|---|---|
| The emergency replacer | No water today; contractor is on the way | Accepting a like-for-like swap without checking whether the old size was right |
| The planner | Pump is 12+ years old and still working | Very little — this is the best position to buy from |
| The pressure complainer | Pressure drops when two fixtures run | Assuming it's the pump. It's often the pressure tank. |
| The low-yield owner | Well runs dry during morning peak | Buying a bigger pump — which makes it worse |
| The new-well owner | Well just drilled; specifying from scratch | Not asking for the well log and yield test |
| The upgrader | Adding bathrooms, irrigation, or a tankless heater | Sizing for today rather than the finished house |
Before you buy a pump — rule these out first
Several cheap fixes produce symptoms that look like pump failure:
- A failed pressure switch, check valve, or capacitor — inexpensive parts
- A waterlogged or undersized pressure tank — frequent cycling wears pumps out early
- A leak in the drop pipe or service line — continuous running at low demand often points here
- A tripped breaker or control box fault
- A dropping water table — if the pumping level fell below the pump intake, the pump is fine
Repair or replace: Replace if the pump is over ~10 years old, has needed repeated repairs, shows significantly reduced flow, or the repair quote exceeds roughly half the cost of replacement. Once a crew has pulled hundreds of feet of pipe, the marginal cost of a new pump is small against the cost of a second pull in two years — which is also why you replace drop pipe and wire during the job rather than reusing them.
The decision framework — seven criteria in the order they matter
| Rank | Criterion | Weight | What it decides |
|---|---|---|---|
| 1 | Well yield vs demand | Critical | Whether a pump can solve your problem at all, or whether you need storage |
| 2 | Pumping water level and TDH | Critical | The head number. Everything else follows from it. |
| 3 | Required flow in GPM | Critical | The flow number, from fixture count and peak demand |
| 4 | Pump type | High | Submersible, jet, or constant pressure. Depth mostly decides this. |
| 5 | Performance curve match | High | Whether the chosen pump actually delivers your GPM at your TDH efficiently |
| 6 | Motor quality vs pull cost | High | On a deep well the labour dwarfs the pump — changes the brand calculus entirely |
| 7 | Wiring, controls, protection | Medium | 2-wire vs 3-wire, dry-run protection, surge protection |
Criterion 1 — Well yield: the ceiling on everything
If demand exceeds yield, the answer is storage — not a bigger pump
A larger pump on a weak well draws the casing down faster, pulls in abrasive sand, and burns out the motor from running dry. Submersible motors are cooled by the water flowing past them — run one dry and it fails quickly. This is the check most often skipped, and it is the one that separates a competent pump selection from an expensive mistake.
| Sustainable yield | What it supports | What to do |
|---|---|---|
| 10+ GPM | A typical household comfortably | Size the pump to demand and move on |
| 5–10 GPM | Most households with sensible fixture use | Size at or below yield; consider peak-shifting |
| 3–5 GPM | A household only with care | Size conservatively; intermediate storage tank worth pricing |
| 1–3 GPM | Not a household on demand alone | Storage system, not a bigger pump |
| Under 1 GPM | Marginal well | Storage plus serious conservation, or a new well |
If you don't know your yield, it's on the well log from the driller. A pump professional can also perform a draw-down test. Either is cheaper than a burned-out motor.
Criterion 2 — Total dynamic head: the number people get wrong
The TDH formula
TDH = pumping water level + pressure requirement + friction losses
- Pumping water level in feet — not well depth, not static water level. This is where the water falls to while the pump is running.
- Pressure requirement: multiply target PSI × 2.31. Fifty PSI = 115.5 feet.
- Friction losses from pipe length, diameter, fittings, and any elevation rise from wellhead to house.
Worked example: 200-ft pumping level + 115.5 ft (50 PSI) + 20 ft friction = 335.5 ft TDH. A well people describe as "200 feet" presents 336 feet of head. Size against depth alone and you under-buy by a third.
| Term | What it actually is | Goes into TDH? |
|---|---|---|
| Well depth | How deep the hole is drilled | No — largely irrelevant on its own |
| Static water level | Where water sits with pump off | Reference only — not the working number |
| Pumping water level | Where water falls to with pump running | Yes — this is the number that goes in |
| Drawdown | Static level minus pumping level | Tells you how hard the well is working |
| Pump setting depth | How far down the pump hangs | Related — but not the same as pumping level |
Criterion 3 — Required flow in GPM
The standard method is fixture counting. Peak demand is what matters, not daily total.
Estimate roughly 1 GPM per water-using fixture. A 3-bed, 2-bath home has 10–12 fixtures → 10–12 GPM target.
Add 1–2 GPM per major appliance as margin (dishwasher, washing machine).
Include irrigation separately — usually the largest single load on any residential well.
Don't forget concurrent uses: a toilet flushing during a shower, for example.
Most residential wells target 8–12 GPM at 40–60 PSI.
Then check against your yield (Criterion 1). The fixture count gives you what the house wants. The yield test gives you what the well can provide. If the first number exceeds the second, you don't have a pump problem — you have a storage problem. This is the single most common way a well system gets specified badly.
Criterion 4 — Pump type
Depth mostly decides this. The physics is not subtle: pushing water is far more efficient than pulling it.
| Type | Depth range | Efficiency | Installed cost |
|---|---|---|---|
| Shallow-well jet | Under 25 ft | 25–45% | $800–$1,800 |
| Deep-well jet | ~80–120 ft max | 25–40% | $1,800–$2,800 |
| Submersible | 25 ft to 500+ ft | 40–55% | $1,500–$5,500+ |
| Constant pressure | Same as submersible | Similar + better part-load | $2,000–$5,500 |
| Hand pump | Shallow | Manual | From ~$160 |
Why deep-well jet pumps have largely lost: A deep-well jet pump recirculates roughly 3–4 gallons for every gallon delivered, dropping efficiency to 25–40%. For wells deeper than ~110 feet, the jet pump's operating costs catch and surpass the higher initial cost of a submersible within 4–6 years on most residential duty cycles. The case for a jet pump today is a genuinely shallow well, a cabin, or a temporary installation where surface-mounted serviceability outweighs efficiency.
Criterion 4a — Constant pressure systems: when they're worth it
A conventional system is two-state: the pump runs at full speed until the tank reaches cut-out pressure, then shuts off. When two fixtures run simultaneously, pressure noticeably drops. A constant pressure system uses a variable-frequency drive (VFD) to modulate motor speed — slow for one faucet, ramping up for three — holding pressure steady under any demand.
| Constant pressure | Conventional | |
|---|---|---|
| Pressure consistency | City-like, steady under simultaneous demand | Cycles between cut-in and cut-out |
| Installed cost | $2,000–$5,500 | Lower |
| Premium over standard | Roughly $1,000–$3,000 for controller and labour | — |
| Motor wear | Soft-start reduces wear | Each start is a high-current surge |
| External VFD retrofit | ~$400–$700 plus a tech to wire it | — |
| Who needs it | 4+ bathrooms, irrigation while showering, tankless water heater | 2-bathroom house with a properly sized pressure tank — adequate and cheaper |
If pressure inconsistency is your complaint, price a larger pressure tank first. It is often the cheaper fix for the same symptom — far cheaper than a VFD system. See the pressure tank sizing guide.
Criterion 5 — The performance curve: the document most installers skip
Every submersible pump has a performance curve — a graph published free by the manufacturer showing exactly how many GPM the pump delivers at different head pressures. This is the single most important document for pump selection, and too many installers skip it in favour of rules of thumb.
The horizontal axis is flow in GPM. The vertical axis is total head in feet. The curve slopes down to the right — as flow rises, available head falls.
Find your TDH on the vertical axis, read across to the curve, read down to see the actual GPM the pump delivers at your head.
Most curves mark an efficiency zone. Your operating point should fall inside it. Running at the extremes wastes energy and shortens pump life.
A pump operating at 60% efficiency uses significantly more electricity than one at 80% to deliver the same water. Grundfos, Franklin Electric, and Pentair publish their curves online. Ask your contractor which curve they used.
Why the curve matters: A well with a 350-foot pumping level delivering at 50 PSI has actual TDH closer to 500 feet. A pump with a 290-foot head rating won't pump at all. The gap between "350-foot well" and "500 feet of TDH" is the arithmetic above — and it's why depth ratings mislead.
Criteria 6 and 7 — Brand economics and wiring
Brand matters differently at different depths, and the reason is labour rather than metallurgy.
| Depth | Pull cost | Brand calculus |
|---|---|---|
| 200 ft | $400–$700 to pull | Budget brands are a defensible risk |
| 400 ft | ~$1,500 in labour just to extract and reinstall | Premium motor starts paying |
| 600 ft | $1,200–$2,200 for hoist time and crew | A 5-year warranty doesn't cover the labour. Buy premium. |
| Brand | Known for | Best for |
|---|---|---|
| Franklin Electric | Industry baseline — OEM component inside many other brands. Sealed windings, stainless hex shafts, built-in lightning arrestors. | Most residential applications |
| Grundfos | Permanent-magnet motors with soft-start electronics and integrated dry-run protection. | Constant pressure, solar, deep wells |
| Goulds (Xylem) | Floating-impeller stacks rated for sand handling. | Grit-prone wells |
| Red Lion | Reliable mid-tier. | Shallow wells, cabins, budget-constrained jobs |
On wiring: a 2-wire submersible puts the starting components inside the sealed downhole motor — cheaper to install, nothing serviceable at the surface. A 3-wire pump puts those components in a surface control box, easier to service without pulling the pump but adds a component above ground. Neither is universally better — ask your contractor which they're quoting and why.
On lifespan claims: sources give 8–15, 12–20, and 20–25 years for quality pumps, and 5–10 for budget alternatives. That spread is too wide to plan against, and every figure comes from someone who sells or installs pumps. The defensible summary: premium motors cost roughly 15–40% more and last meaningfully longer — and the deeper your well, the more that difference is worth.
Understanding the terms
| Term | What it means | Why it matters |
|---|---|---|
| GPM | Gallons per minute — flow rate | One of the two numbers that define a pump |
| TDH | Total dynamic head, in feet | The other one |
| Static water level | Water level with pump off | A reference, not the sizing number |
| Pumping water level | Water level while pump runs | The static lift that goes into TDH |
| Well yield | Sustainable flow the aquifer delivers | The ceiling on everything |
| Drawdown | Static level minus pumping level | How hard the well is working |
| Performance curve | Published GPM-vs-head graph | The document that actually selects the pump |
| WHP / BHP | Water HP and brake HP. WHP = GPM × TDH ÷ 3960. BHP = WHP ÷ efficiency. | How to check a HP recommendation |
| Wire-to-water efficiency | Useful hydraulic output per unit of electricity in | Submersibles 40–55%; shallow jets 25–45% |
| Stage | One impeller in a multi-stage pump | Each adds ~16–23 ft of head; a 300 ft lift stacks 12–18 stages |
| 2-wire / 3-wire | Where the starting components live — downhole or in a surface box | Affects installation cost and serviceability |
| VFD | Variable-frequency drive — modulates motor speed | The technology behind constant pressure systems |
| Short cycling | Pump starting and stopping too frequently | The main avoidable cause of premature motor failure |
| Dry run | Pump operating without water | Destroys submersible motors — they are water-cooled |
The arithmetic — if you want to check a contractor's quote
Water HP and Brake HP
WHP = GPM × TDH ÷ 3960
BHP = WHP ÷ efficiency
Worked example: 10 GPM at 336 ft TDH → WHP = 10 × 336 ÷ 3960 = 0.85. At 45% efficiency: 0.85 ÷ 0.45 = 1.9 BHP. At 55% efficiency: 0.85 ÷ 0.55 = 1.5 BHP. So a 1.5 to 2 HP motor — confirmed against the performance curve. The same well can legitimately be quoted with two different motor sizes depending on the pump's efficiency at that duty point.
Depth-to-HP rules of thumb — and their limits
| Depth guideline | Commonly cited HP | Treat it as |
|---|---|---|
| Under 100 ft | ½ HP | A sanity check on a quote — not a specification |
| 100–200 ft | ¾ HP | Same |
| 200–300 ft | 1 HP | Same |
| 300–500 ft | 1.5–2 HP | Same |
| Any depth | What the curve says at your TDH and GPM | The actual answer |
These tables are useful for one thing: noticing when a quote is wildly out of line. If someone proposes ½ HP for a 400-foot well or 3 HP for a 120-foot well, something needs explaining. They are not a substitute for the calculation.
What it costs in 2026
| Scenario | Installed cost | Notes |
|---|---|---|
| National average replacement | $1,500–$2,827 | Plus ~$500–$1,000 per 100 ft of depth |
| Shallow-well jet | $800–$1,800 | Surface-mounted, simplest job |
| Deep-well jet | $1,800–$2,800 | Two pipes, more complexity |
| Submersible, typical | $1,500–$4,000 | Pump $400–$1,500 · pipe/fittings $300–$800 · wiring $200–$500 · labour $800–$1,500 |
| Submersible, 300+ ft | $2,800–$5,500+ | Hoist equipment, crew, full pipe and wire replacement |
| Constant pressure system | $2,000–$5,500 | Adds roughly $1,000–$3,000 over standard |
| Drop pipe and wire | $1–$3 per linear foot | Replace during the job — don't reuse old runs |
| Pump pull only, 600 ft | $1,200–$2,200 | Hoist time and crew — doesn't include a new pump |
Twenty-year cost — budget vs premium vs constant pressure
Modelled for a 250-foot well serving a 3-bed, 2-bath household. Planning ranges, not quotes.
| Cost line | Budget pump | Premium pump | Constant pressure |
|---|---|---|---|
| Pump | $300–$500 | $600–$1,000 | $900–$1,600 |
| Pipe, wire, fittings | $500–$1,100 | $500–$1,100 | $500–$1,100 |
| Controller / VFD | — | — | $400–$700 |
| Labour | $800–$1,500 | $800–$1,500 | $1,000–$2,000 |
| First job total | $1,600–$3,100 | $1,900–$3,600 | $2,800–$5,400 |
| Expected service life | 5–10 years | 12–20 years | 10–15 years |
| Replacements in 20 years | 2 to 3 | 1 to 2 | 1 to 2 |
| 20-year total (estimated) | $4,800–$9,300 | $3,800–$7,200 | $5,600–$10,800 |
The conclusion that holds across every source: The pump is rarely where the money is. Labour, depth, and doing the job twice are where the money is. Correct sizing and a decent motor are the two highest-return decisions available to you. The cheapest quote is a poor proxy for the cheapest outcome.
Red flags and common mistakes
| Mistake | What happens | The fix |
|---|---|---|
| Sizing on well depth alone | Under-buying by a third or more once pressure and friction count | Calculate TDH from pumping water level |
| Using static level instead of pumping level | Systematically undersized head | Ask for the pumping level, measured |
| Buying a bigger pump for more pressure | Dry running, sand ingestion, burned motor | Pressure comes from the switch setting and tank, not pump size |
| Ignoring well yield | A pump that outruns the aquifer | Yield test first; storage if demand exceeds it |
| Skipping the performance curve | A pump that cannot deliver at your head | Ask which curve was used and at what duty point |
| Reusing old drop pipe and wire | A repeat failure and a second pull | Replace during the job — it's $1–$3 per foot |
| Like-for-like replacement without checking | Repeating whatever mistake was made last time | Re-derive GPM and TDH from scratch |
| Cheapest quote on a deep well | A 1-year warranty against a $1,500 pull | Weigh warranty against pull cost |
| Ignoring the pressure tank | Short cycling that kills a new pump | Size the tank to the pump's GPM |
| Treating a pressure complaint as a pump problem | Replacing an adequate pump | Diagnose the switch, tank, and check valve first |
| Non-itemised quote | No way to compare or see what was skipped | Always get itemised quotes showing pump, labour, and parts |
| No surge protection on a deep pump | Lightning damage to an expensive downhole motor | Ask about arrestors; some motors include them |
14 questions to ask before signing a quote
Several of these are questions about whether the contractor did the work of sizing at all. The answers separate professionals from parts-swappers quickly.
What is my well's sustainable yield in GPM, and how was it determined?
What is my pumping water level, and did you measure it or estimate it?
What total dynamic head did you calculate, and what were the three components?
What flow rate did you size for, and how did you arrive at it?
Which manufacturer performance curve did you use, and where does my duty point fall on it?
Is that duty point inside the pump's efficiency zone?
What horsepower, and why that rather than one size up or down?
Which brand and model, and what is the warranty term?
Is this a 2-wire or 3-wire pump, and why?
Are you replacing the drop pipe and wire, and is that in the quote?
Will you check or replace the pressure tank, and is its drawdown matched to this pump?
Does the installation include dry-run protection and surge protection?
What will you check the amp draw against after installation?
Can I have an itemised quote separating pump, pipe, wire, controls, and labour?
| Question topic | A good answer sounds like | A bad answer sounds like |
|---|---|---|
| Well yield | A GPM figure and how it was measured | "It should be fine" |
| Pumping level | A measured depth in feet | The well depth restated |
| TDH | A number with its three components broken out | "It's a 250-foot well" |
| Performance curve | A named model and a duty point | "That's what we always use for this depth" |
| Horsepower choice | A reason tied to the calculation | "Bigger is better" |
| Pipe and wire | Included, with linear footage priced | Silence, or reuse of the existing run |
| Pressure tank | They ask about it unprompted | Not mentioned at all |
| Quote format | Itemised by component | A single number |
Recommendations by buyer profile
The emergency replacer
You have the least leverage. Protect the two decisions that matter most: insist on a measured pumping water level before agreeing to a size, and insist that drop pipe and wire are replaced rather than reused. Beyond that, take a competent pump from a reputable brand and get your water back.
Pick: Whatever a licensed contractor can install today, sized from a measured pumping level, with new pipe and wire.
The planner
The best position of any profile here. Get the well log, get a yield test, calculate TDH properly, and ask two or three contractors which performance curve they used. Then buy a premium motor — the price difference at your leisure is a few hundred dollars against a job you'd rather not repeat.
Pick: A curve-matched premium submersible, installed on a scheduled visit, with the pressure tank replaced at the same time if it's old.
The pressure complainer
Before spending anything on a pump, diagnose the pressure tank and switch. Pressure that sags when two fixtures run is the classic signature of a tank whose drawdown is too small for the pump — a much cheaper fix. If the tank checks out and you want city-like pressure, a constant pressure system is the real answer at $1,000–$3,000 over a standard pump.
Pick: Tank first. VFD second. New pump only if the pump is actually failing.
The low-yield owner
A bigger pump is the intuitive answer and the wrong one. If demand exceeds yield, a larger pump draws the well down faster, pulls in sand, and risks burning out from running dry. Your answer is an intermediate storage tank filled slowly and continuously, with a separate pressure pump serving the house.
Pick: Storage, plus a modestly sized pump at or below your sustainable yield, with a low-water cutoff for dry-run protection.
The new-well owner
You have something almost nobody else has: fresh, measured data from the driller. Get the well log, the static level, the tested yield, and the recommended pump setting depth in writing — and make sure whoever specifies the pump uses all four. This is the one time in the system's life when sizing can be done from real numbers rather than inference.
Pick: Whatever the curve says, specified against the driller's own test data.
The upgrader
Size for the finished house, not the current one. Adding two bathrooms is roughly 4–6 more GPM of peak demand, and irrigation is usually the largest single load on any residential well. Check that number against your yield before assuming the pump is the constraint.
Pick: Recalculate GPM for the completed project, verify against yield, then match the curve.
What to verify after installation
Amp draw checked against the motor nameplate specification.
Measured flow rate at a hose bib, timed with a bucket, compared against the design GPM.
Pressure switch cut-in and cut-out settings confirmed and recorded.
Pressure tank pre-charge set to 2 PSI below cut-in, with the tank drained.
Pump run time per cycle timed — it should meet the minimum for the motor size, not seconds.
Well disinfected after the work if the contractor opened the casing — retest for coliform.
Documentation retained: pump model, horsepower, setting depth, wire size, and install date.
Write the setting depth on the well cap. Pump model, horsepower, setting depth, wire gauge, and install date — on a label inside the well house or on the pressure tank. The next person to work on this system, possibly a decade from now, will save an hour of guessing, and you'll have the data to size the replacement properly.
Common questions
What two numbers actually size a well pump?
Required flow in GPM and total dynamic head in feet. Depth alone does not size a pump — a well described as 200 feet deep commonly presents 335+ feet of TDH once pressure and friction are counted.
What happens if I oversize my well pump?
An oversized pump draws water faster than the well can recharge, risks running the casing dry, pulls in abrasive sand, and burns out the motor. Submersible motors are water-cooled — run one dry and it fails quickly. Oversizing is not a safe hedge.
My well runs dry during peak usage. Do I need a bigger pump?
No — you need storage. If your demand exceeds what the aquifer can sustainably deliver, a bigger pump draws it down faster and risks burning out from running dry. An intermediate storage tank filled slowly and continuously, with a separate pressure pump serving the house, is the correct solution.
Is a constant pressure pump worth the extra cost?
For a household with 4+ bathrooms, irrigation running concurrently with showers, or a tankless water heater — yes. For a 2-bathroom house with a properly sized pressure tank — likely not. Price a larger pressure tank first; it often solves the same symptom at a fraction of the cost.
Should I replace the drop pipe and wire when I replace the pump?
Yes. Old drop pipe and wire are the most common cause of a repeat pull. At $1–$3 per linear foot, replacing them while the crew is already on site is far cheaper than a second pull in two years. Insist it's in the quote.
Related guides
- Well water pressure tank sizing guide — the component that works with your pump
- Best submersible well pumps — reviewed by depth and flow
- Best shallow well pumps — for wells under 25 feet
- Well pump replacement cost — what to expect in 2026
- Well pump pressure switch troubleshooting — diagnose before you replace
- Well and pump repair guide — when to fix vs replace