Quick Answer
Okay so here's the quick version. If your water heater's pressure relief valve is dripping or your pipes are banging, your expansion tank is probably shot. Nine times out of ten, the rubber bladder inside has failed and the tank is full of water—they call it 'waterlogged.' You can check by tapping it; if it sounds solid all over, it's bad. Or press the little air valve on top—if water comes out, it's toast. Replacement is the only real fix. You can do it yourself for around $50-$120 for the tank, but a pro will charge you $300-$650.
Common Symptoms
Possible Causes
Step-by-Step Diagnosis
Step 1
The Eyeball Test. Look for rust, corrosion, or water stains on or below the tank.
Step 2
The Tap Test. Knock on the top and bottom of the tank. It should sound hollow on top and solid on the bottom. If it's solid all over, it's waterlogged.
Step 3
Check the Air Valve. Briefly press the pin on the Schrader valve. If water squirts out, the internal diaphragm has failed and the tank needs replacement.
Step 4
Actually Check the Pressure. With system water pressure relieved, use a tire gauge to check the air pressure. It should match your home's incoming water pressure (typically 40-80 PSI).
DIY vs Professional Costs
| Repair Type | DIY Cost | Professional Cost | Time Required |
|---|---|---|---|
Adjusting Air Pressure | $0 - $20 | $75 - $150 | 30 minutes |
Expansion Tank Replacement | $50 - $120 | $300 - $650 | 1-2 hours |
New Installation (if none exists) | $70 - $150 | $350 - $600+ | 2-4 hours |
When to Call a Professional Water Heater
- If water squirts out of the air valve, the tank is shot and needs replacing.
- If your water heater's T&P relief valve is discharging frequently, indicating a potentially dangerous pressure situation.
- If the tank itself is visibly leaking from a rust spot on its body.
- If you don't have an expansion tank at all and need one installed to comply with plumbing codes and protect your system.
- If you are uncomfortable with plumbing work, shutting off water, and draining parts of your system.
Prevention Tips
- Check the Air Pressure Annually: Relieve water pressure and use a tire gauge to ensure the tank's air pressure matches your home's water pressure.
- Do the Tap Test: Every six months, tap the tank to ensure it still sounds hollow on top and solid on the bottom.
- Keep an Eye on It: Regularly inspect the tank and its connections for any signs of rust, corrosion, or drips.
Frequently Asked Questions
Related Guides
Lack of hot water heater maintenance leading to decreased efficiency, premature failure, and reduced lifespan Troubleshooting & Fixes
Inefficient water heater operation due to insufficient insulation, leading to higher energy consumption and increased utility bills. Troubleshooting & Fixes (2024 Guide)
Is your water heater bleeding heat and money? Our veteran tech's guide shows you how to troubleshoot and fix poor insulation for lower utility bills. Easy fixes inside.
Safely and effectively shutting down a water heater during an emergency or for maintenance to prevent further damage or hazards. Troubleshooting & Fixes
Water Heater TPR Valve Leaking: Troubleshooting & Fixes (2024 Guide)
Your water heater's TPR valve leaking? A veteran tech explains why it's happening, how to fix it, and when to call a pro. Learn the real causes and costs.
Water Heater Expansion Tank Problems (Troubleshooting & Fixes from a 25-Year Vet)
Hearing banging pipes or a dripping T&P valve? Your water heater expansion tank might be shot. A 25-year vet shows you how to diagnose and fix it the right way.
Noisy Water Heater (Popping, rumbling, hissing, whining, banging sounds) Troubleshooting & Fixes
Need Professional Help?
Find top-rated water heater experts in your area