The pump is where the well meets the house. A good installer sizes it from data, not from a rule of thumb about horsepower. This page lists the information that drives the decision so you can bring it to the conversation and check the proposal. It does not cover electrical or installation work, which should be done by licensed professionals.
What limits well pump size?
- What the household needs at peak. Penn State Extension suggests designing a water system to deliver a full day's use within a 2-hour peak period, with planning flows from about 6 GPM for a small home to 18 GPM for a large one. Penn State Extension: Water System Planning — Estimating Water Needs
- What the well can supply. Yield is the maximum rate a well can be pumped without lowering the water below the pump intake. Penn State Extension: Using Low-Yielding Wells
The pump's capacity should fit within both. If peak demand is higher than the well's yield, the answer is storage, not a bigger pump.
What does the installer need to size a well pump?
| Information | Where it comes from |
|---|---|
| Tested yield | The contractor's yield test report |
| Static and pumping water levels | The yield test and the well log |
| Well depth and casing diameter | The well log |
| Distance and height to the house | Site plan |
| Household size and fixtures | You |
| Desired pressure range | You and the installer |
| Planned treatment equipment | The water test result |
See well pump tests for what the yield report should contain and how to read a water well log for the depth fields.
Submersible or jet pump?
The U.S. Environmental Protection Agency describes jet pumps as mounted above ground and typically used for shallow wells of 25 feet or less, and submersible pumps as placed inside the casing and typically used for deep wells. EPA: Learn About Private Water Wells [EPA-LEARN source note]
What size pressure tank do you need?
The pressure tank stores a little water under pressure so the pump doesn't start every time a tap opens. Only about 20 percent of its capacity is usable: a 42-gallon tank delivers about 8 gallons before the pump restarts. Penn State Extension: Using Low-Yielding Wells Guidance for inspectors describes a normal pump cycle with no water running as 1 to 2 minutes, and treats under 45 seconds or over 2 minutes 15 seconds as worth investigating. Water Systems Council: wellcare Guide to Evaluating Water Wells (for home inspectors) Connecticut guidance recommends a minimum pump run time of at least two minutes. Connecticut DPH: Private Well Guidance for Determining Well Safe Yield (2009) [PSU-LOWYIELD source note] [WSC-INSPECTOR source note] [CT-SAFEYIELD source note]
What if the well yield is lower than peak demand?
If the well cannot meet peak demand, an intermediate storage tank lets a modest pump fill storage steadily while a second pump supplies the house. Penn State Extension suggests about 100 gallons of storage per household member as a rule of thumb. Penn State Extension: Using Low-Yielding Wells See low-yield well options. [PSU-LOWYIELD source note]
Common well pump sizing mistakes
- Choosing by horsepower. Horsepower alone doesn't tell you flow at your depth and pressure. Ask for the pump's performance at your total lift.
- Oversizing the pump. A pump that can move more water than the well yields draws the level down fast and can run dry.
- Ignoring the pressure tank. A tank that is too small makes the pump start and stop too often, which wears it out. Short cycles under about 45 seconds are a warning sign in inspection guidance. Water Systems Council: wellcare Guide to Evaluating Water Wells (for home inspectors)
- Forgetting treatment equipment. Filters and softeners add pressure loss; tell the installer what you plan to install.
- Setting the pump without test data. Without a yield test, pump depth and size are guesses; see well pump tests.
Submersible vs. jet pump at a glance
| Submersible pump | Jet pump | |
|---|---|---|
| Where it sits | Inside the well casing, below the water level | Above ground, in a pump house or basement |
| Typical use (EPA) | Deep wells | Shallow wells of about 25 feet or less |
| Noise | Quiet; it's underground | Audible where it is mounted |
| Service | Pulled up out of the well for repair | Accessible above ground |
Source for the typical uses: EPA: Learn About Private Water Wells. [EPA-LEARN source note]
Who installs a well pump?
Pump work is often licensed separately from drilling. Texas, for example, issues Pump Installer licenses with endorsements for single-phase, three-phase and turbine pumps. TDLR: Water Well Driller and/or Pump Installer License Check who is licensed to install pumps where you live, and include the pump system as its own line when you compare complete well installation costs. [TDLR-APPLY source note]
Common questions
How do I know what size well pump I need?
Give the installer your tested yield, water levels, well depth and diameter, and your household size and fixtures. They match the pump's flow and lift to the lower of your peak demand and the well's yield. Avoid choosing by horsepower alone.
Submersible or jet pump?
EPA describes jet pumps as mounted above ground and typically used for shallow wells of 25 feet or less, and submersible pumps as placed inside the casing for deep wells. Most new drilled wells use submersible pumps.
What size pressure tank do I need?
Your installer will size it to the pump and demand. Remember that only about 20 percent of a pressure tank's capacity is usable, so a 42-gallon tank delivers about 8 gallons between pump starts. Tanks that are too small make the pump cycle too often.
Should the pump installer be licensed?
In many states, yes. Some states license pump installers separately from drillers; Texas, for example, issues separate pump installer licenses. Ask the authority that licenses well contractors where you live.
Sources & claim context
Citations mark where guidance is grounded. They are general resources dated on retrieval, not guarantees for any property, project, price, licensure, permit or yield. No expert, attorney or reviewer signoff is claimed by this site.
EPA: Private Wells · EPA · accessed 2026-10-10
https://www.epa.gov/privatewells
Does not specify local testing/permit rules or guarantee safety
EPA: Learn About Private Water Wells · EPA · accessed 2026-10-10
https://www.epa.gov/privatewells/learn-about-private-water-wells
Typical depths are general descriptions, not local requirements
Penn State Extension: Using Low-Yielding Wells · Penn State Extension · accessed 2026-10-10
https://extension.psu.edu/using-low-yielding-wells
Cost figures in the article are Pennsylvania-era estimates; not quotes
Penn State Extension: Water System Planning — Estimating Water Needs · Penn State Extension · accessed 2026-10-10
https://extension.psu.edu/water-system-planning-estimating-water-needs
Planning guideline, not a code requirement; local rules may differ
Water Systems Council: wellcare Guide to Evaluating Water Wells (for home inspectors) · Water Systems Council (wellcare) · accessed 2026-10-10
Guideline distances are not legal requirements; check state rules on who may inspect
Connecticut DPH: Private Well Guidance for Determining Well Safe Yield (2009) · Connecticut Department of Public Health · accessed 2026-10-10
Connecticut example; 2009 publication
TDLR: Water Well Driller and/or Pump Installer License · Texas Department of Licensing and Regulation · accessed 2026-10-10
https://www.tdlr.texas.gov/wwd/apply-driller-installer.htm
Licensing details only; not a license lookup
Claims are grounded in the dated source notes above; project-specific price, yield, licensure and permit answers require site-specific and local verification.