A water heater expansion tank, installed
The small tank on top of this water heater is the expansion tank. Water grows as it heats, and the expansion tank gives that extra water somewhere to go instead of pushing on the heater and your pipes.
5.0 stars across 1,130 reviews
Get your price in writing
Send this and the office calls or texts you back to set a time.
We’ll call or text this number about your request. By sending it you agree to our terms and privacy policy.
Rather talk now? (703) 997-9757
Licensed and insuredVirginia Class A contractor #2705192276
24/7 emergency serviceWe answer day or night, and we will tell you honestly when we can get there.
Our own plumbers, our own trucksNobody here is a subcontractor with a magnet on the door
The price is settled before the workYou see the number in writing before anything is taken apart
From one of our jobs
The small tank on top, and what it does
Right now: Tap the expansion tank. A hollow sound is good. A dull thud means it’s full of water and has failed.
Most homes here have a valve on the main water line that stops water from flowing back to the street. That makes the plumbing a closed system, so when the heater warms a tank of water, the pressure has nowhere to go. The expansion tank takes it.
If your relief valve drips, or faucets spit when the heater has just run, ask about the expansion tank. We look at it on every water heater we replace.
Quick answers
What people ask about expansion tanks
What is the small tank on top of my water heater?
The expansion tank. It gives water somewhere to go when it heats up and grows, so the pressure doesn’t build in your pipes.
Do I need an expansion tank on my water heater?
If your home has a check valve or pressure reducing valve on the main line, as most here do, yes. Many counties require one with a new water heater.
How do I know if my expansion tank is bad?
Tap it. The top should sound hollow. If the whole tank sounds solid, it’s full of water. A dripping relief valve on the water heater is the other sign.
Who installs expansion tanks in Northern Virginia?
Call SwiftPro at (703) 997-9757. We check the expansion tank on every water heater we replace.
Seeing this at your house?
Tell us what you’re seeing. We’ll tell you what it is and what the fix costs, in writing.
What it costs
What we charge to replace a water heater
Read and watch next
More on this from SwiftPro
More real photos from our jobs
Seeing this at your house?
Want us to take a look at yours?
Tell us what you’re seeing. We’ll give you a time and a price in writing before any work starts.
SwiftPro Heating, Cooling & Plumbing
4230 Lafayette Center Dr N, Chantilly, VA 20151
44679 Endicott Dr, Suite 211, Ashburn, VA 20147
SwiftPro Plumber & Water Heaters
4200 Lafayette Center Dr, Suite N, Chantilly, VA 20151
Virginia Class A contractor license #2705192276