How to Choose a Well Pump — Complete Guide for Southern Maryland Homeowners
Everything you need to know about choosing a well pump for a Southern Maryland property — from Terry Foster Jr., MD Master Plumber #98433. Sizing, brands, and what to avoid.
Terry Foster Jr.
MD Master Plumber #98433 · Deep Dive Plumbing Maryland
Key Takeaways
- Most Southern Maryland wells need a submersible pump (50–300 ft depth)
- Pump sizing requires measuring well yield, static water level, and household demand
- Grundfos and Franklin Electric are the most reliable brands for this area
- Never oversize a pump — it will run the well dry
- A constant pressure system is worth considering for 3+ bathroom homes
Step 1 — Know Your Well
Before choosing a pump, you need: well depth (from the well driller's report or a measurement), static water level (how deep the water sits when the pump is off), well yield (gallons per minute the well produces), and casing diameter (most residential wells are 4 or 6 inches). If you do not have this information, we can measure it during a service call.
Step 2 — Choose the Pump Type
For wells deeper than 25 feet (virtually all Southern Maryland residential wells), a submersible pump is the correct choice. Submersible pumps push water up from below — far more efficient than jet pumps, which pull water up from above. Jet pumps are only appropriate for shallow wells under 25 feet.
Step 3 — Size the Pump Correctly
Pump sizing involves calculating total dynamic head (TDH) — the total resistance the pump must overcome. TDH = static water level + drawdown + friction losses + pressure head. We calculate this before recommending a pump. Oversizing is a common mistake — a pump that moves more water than the well produces will run dry, overheat, and fail within months.
Step 4 — Choose the Right Horsepower
Most residential wells use 1/2 HP to 1 HP submersible pumps. The right horsepower depends on well depth, flow rate needed, and TDH. A 1/2 HP pump is appropriate for wells under 150 feet with moderate demand. A 3/4 HP or 1 HP pump is needed for deeper wells or higher demand. We size to the well, not to a standard.
Step 5 — Consider a Constant Pressure System
A standard pump delivers water in a pressure band (typically 40–60 PSI). When multiple fixtures run simultaneously, pressure drops. A constant pressure system (Grundfos CU301 or similar) uses a variable-speed controller to maintain steady pressure regardless of demand. For households with 3+ bathrooms or irrigation systems, the upgrade is worth considering.
Common Mistakes to Avoid
- Oversizing the pump — runs the well dry
- Ignoring water chemistry — corrosive water destroys standard pump materials
- Skipping the pressure tank sizing — an undersized tank causes rapid cycling that kills pumps
- Choosing a cheap brand — saves money upfront, costs significantly more in an early emergency replacement
- Not installing a Pump Saver — a device that prevents dry-run damage
Frequently Asked Questions
How much does a well pump replacement cost in Maryland?
Well pump replacement cost in Southern Maryland varies based on pump depth, pump size, and whether the pressure tank also needs replacement. Call for a free estimate — we provide clear written pricing before beginning any work.
How long does a well pump last?
Most submersible well pumps last 10–15 years in normal conditions. In Southern Maryland, corrosive water chemistry (low pH, high iron) can shorten this to 8–12 years. Pumps that cycle frequently due to an undersized pressure tank also fail earlier.
What is a Pump Saver and do I need one?
A Pump Saver (Franklin Electric) monitors pump current and shuts the pump off if it detects dry-run conditions (no water in the well). It can prevent a costly pump replacement if your well runs low during drought conditions. We recommend it for all new pump installations.
Can I install a well pump myself?
Replacing a submersible well pump requires pulling the pump from the well (which requires proper equipment for deep wells), electrical work, and proper torque on the drop pipe connections. We do not recommend DIY pump replacement — an improperly installed pump can damage the well casing or fail immediately.
What is a constant pressure well system?
A constant pressure system uses a variable-speed pump controller to maintain steady water pressure regardless of demand. Instead of cycling on and off between 40 and 60 PSI, the pump runs continuously at variable speed to maintain exactly the pressure you set. The result is steady pressure even when multiple fixtures run simultaneously.
Related Resources
Need a Well Pump Replaced?
We size every pump to your specific well — depth, yield, and water chemistry. Same-day emergency service available throughout Southern Maryland.