How to Check a Well Pressure Tank: Complete Diagnostic Guide

Your pressure tank is one of the most critical components in your well system, yet it's often overlooked until problems arise. This essential piece of equipment stores pressurized water, reduces pump cycling, and provides consistent pressure throughout your home. When a pressure tank fails, you'll notice symptoms ranging from rapid pump cycling to pressure fluctuations and premature pump failure. This comprehensive guide will teach you how to properly inspect, test, and diagnose your pressure tank to ensure reliable operation.

Understanding How Pressure Tanks Work

Before diving into diagnostics, it's important to understand what happens inside your pressure tank. Modern residential pressure tanks are typically bladder or diaphragm tanks. Inside the steel shell, a flexible rubber bladder or diaphragm separates two chambers: one contains water from your well pump, the other contains compressed air.

When the pump runs, water fills the bladder, compressing the air chamber. This stored pressure pushes water out to your fixtures when you open a faucet. The compressed air acts like a spring, maintaining pressure even when the pump isn't running. This design allows your pump to rest between cycles, extending its life and providing steady pressure.

Key Tank Specifications

• Tank capacity: Total volume of the tank (not usable water)
• Drawdown: Amount of water the tank delivers between pump cycles
• Precharge: Air pressure in the tank when empty of water
• Working pressure: Operating pressure range matching your switch settings

Signs Your Pressure Tank May Have Problems

Watch for these warning signs that indicate tank issues:

Rapid Pump Cycling

If your pump turns on and off every few seconds or with minimal water use, the tank has likely lost its air precharge or the bladder has failed. This "short cycling" is the most common symptom of tank failure.

Pressure Fluctuations

Noticeable pressure changes during water use—strong flow that suddenly weakens—suggests the tank isn't maintaining proper pressure.

Waterlogged Tank

A tank full of water with no air cushion is "waterlogged." The tank will feel heavy, and you may hear water sloshing when you tap or rock it.

Water in the Air Valve

If water comes out when you check the air valve (Schrader valve) at the top of the tank, the bladder has ruptured.

Low Water Pressure

Consistently low pressure can result from improper precharge settings or a failing tank.

Visible Damage

Rust, corrosion, bulging, or leaks on the tank exterior indicate serious problems requiring replacement.

Step-by-Step Tank Inspection

Step 1: Visual Inspection

Start with a thorough visual examination:

• Check for rust, corrosion, or paint bubbling
• Look for water stains indicating leaks
• Inspect connections for drips or mineral deposits
• Check the tank's support and mounting
• Look for bulges or deformities in the tank shell

Step 2: The "Knock Test"

A simple but revealing test:

1. Knock on the tank at various heights
2. A properly charged tank will have different sounds: hollow/resonant where air is, solid/dull where water is
3. The water level should be roughly in the lower third to half of the tank when the system is at rest
4. If the entire tank sounds solid, it's likely waterlogged

Step 3: Check the Air Pressure

This is the most important diagnostic step:

1. Turn off power to the well pump at the breaker
2. Drain system pressure by opening a faucet until flow stops completely
3. Locate the air valve (Schrader valve like on a tire) on top of the tank
4. Remove the cap and check for water spray. If water sprays out, the bladder is ruptured—the tank needs replacement
5. Use a tire pressure gauge to check the air pressure
6. Record the reading and compare to specifications

Correct Precharge Pressure

The tank's air precharge should be 2 PSI below your pressure switch's cut-in setting:

• 30/50 PSI switch → 28 PSI precharge
• 40/60 PSI switch → 38 PSI precharge
• 20/40 PSI switch → 18 PSI precharge

If precharge is low but no water came from the valve, you can add air with a standard tire pump or compressor. If precharge is too high, release air until it's correct.

Step 4: Monitor Pump Cycling

After checking and correcting precharge:

1. Restore power and let the system pressurize
2. Open a faucet and time how long before the pump starts
3. Close the faucet and time how long until the pump stops
4. A properly functioning system should allow several minutes of moderate water use before the pump cycles

Step 5: Drawdown Test

Measure actual tank performance:

1. Let the pump fill the tank completely (pressure at cut-out)
2. Turn off power to the pump
3. Open a faucet and collect water in measured containers
4. Continue until the pump would normally turn on (pressure at cut-in)
5. The total collected is your drawdown capacity

Compare this to the tank's rated drawdown. If actual drawdown is significantly less (say, 50% or less of rated), the tank is not performing properly.

Understanding Tank Capacity vs. Drawdown

A common misconception is that a "20-gallon tank" provides 20 gallons of water. In reality, actual usable water (drawdown) is much less due to the air cushion. Typical drawdown percentages:

• Standard tanks: About 25-30% of total capacity
• High-acceptance tanks: About 35-40% of total capacity

For example, a standard 44-gallon tank might provide 10-14 gallons of drawdown, not 44 gallons.

Common Pressure Tank Problems and Solutions

Problem: Low Air Precharge

Symptoms: Rapid cycling, waterlogged feel

Cause: Air naturally permeates through the bladder over time

Solution: Drain tank, add air to correct pressure, recheck periodically

Problem: Ruptured Bladder

Symptoms: Water from air valve, severe short cycling, tank entirely waterlogged

Cause: Age, manufacturing defect, over-pressurization, or chemical damage

Solution: Replace the tank (bladders are generally not field-replaceable)

Problem: Excessive Precharge

Symptoms: Reduced drawdown, pump cycles quickly even though tank seems to have air

Cause: Over-inflation or mismatched pressure settings

Solution: Release air to proper level (2 PSI below cut-in)

Problem: Tank Corrosion

Symptoms: Rust, leaks, weakened shell

Cause: Age, condensation, water chemistry

Solution: Replace the tank; corroded tanks can fail catastrophically

Problem: Undersized Tank

Symptoms: Frequent but normal cycling, pump starting with light use

Cause: Tank too small for household demand

Solution: Install a larger tank or add a second tank in parallel

Maintaining Your Pressure Tank

Regular maintenance extends tank life and ensures reliable operation:

Monthly

• Listen for normal pump cycling patterns
• Check for visible leaks or corrosion
• Note any pressure fluctuations during use

Quarterly

• Check and record system pressures (cut-in and cut-out)
• Perform the knock test

Annually

• Check and adjust air precharge
• Inspect all connections and fittings
• Test the pressure relief valve if equipped
• Consider professional inspection

When to Replace Your Pressure Tank

Plan for replacement when:

• Bladder has ruptured (water from air valve)
• Tank cannot hold air precharge
• Significant rust or corrosion is present
• Tank is over 10-15 years old (preventive replacement)
• Tank shows bulging, dents, or structural damage
• You're experiencing repeated problems despite maintenance

Don't wait for catastrophic failure—a burst pressure tank can cause flooding and property damage. Proactive replacement is much less costly than water damage repairs.

Choosing a Replacement Tank

If replacement is needed, consider:

• Drawdown capacity: Match or exceed your current tank's performance
• Physical size: Ensure the new tank fits the available space
• Connection size: Match existing plumbing connections
• Quality: Choose reputable brands with good warranties
• Pressure rating: Must exceed your maximum system pressure

Popular quality brands include Well-X-Trol, Flexcon, and AO Smith. Investing in a quality tank pays off in longevity and reliability.

DIY vs. Professional Service

Checking your pressure tank is well within DIY capabilities for most homeowners. However, consider professional help for:

• Tank replacement (especially for large tanks)
• Diagnosing complex system issues
• Sizing calculations for new installations
• When working in confined spaces
• If you're uncomfortable with the procedures

Conclusion

Your pressure tank plays a vital role in your well system's performance and longevity. Regular inspection and maintenance—particularly checking and maintaining proper air precharge—can prevent common problems like rapid pump cycling and premature pump failure. By understanding how your tank works and knowing what symptoms to watch for, you can catch problems early and ensure reliable water service for your home.

Remember: a few minutes of preventive maintenance can save hours of hassle and hundreds of dollars in repairs. Make pressure tank inspection part of your regular home maintenance routine.

Need help with your pressure tank? Southern California Well Service provides expert diagnosis, repair, and replacement services. Contact us at (760) 463-0493 or visit www.scwellservice.com to schedule an inspection today.