Replacing a Thermal Expander
A few days back, my wife woke up in the middle of the night to make our daughter a bottle and noticed that the faucet was sputtering. Confused (and half-asleep) I told her to make the bottle with some water we keep in the pantry and not worry about it. My first thought was water main break, but I didn’t think too much of it.
Morning came and more air was coming through the pipes. Naturally, we called our local water provider, Shiloh Water System. The gentleman that answered the phone was extremely courteous and patient while he explained to me that there was no way the air was caused by a water main break. Great, I thought, now I have to call a plumber — on a Sunday. We all know what that amounts to: $$$$. Au contraire! He explained to me that what would likely be causing the problem is known as a Thermal Expansion Absorber, or Thermal Expander. To verify this was the cause of the problem, he suggested testing the valve (just like a bike tire) with a tire pressure gauge to see if water came out. Sure enough! He explained that I could replace this “fairly easily” and my problem would be solved. I thanked him for all his help and went to the computer to start researching.
Thermal Expansion Absorber? What’s That?
After some Googling I found out that the expansion tanks are sized based on the size of your water heater. Also, in my engineer ways, I wanted to learn the purpose of the tank. It’s quite simple, actually. As water heats up in the water heater, it expands but it needs someplace to go. The tank, which is pressurized with air, allows the water to expand against the rubber diaphragm. Failure to use the tank could result in the hot water heater expanding or even exploding! Well, I guess I’ll be needing that then!
Purchasing and Replacing the Tank
Armed with the proper capacity of the water heater (40 gallons in our case) and an idea of our incoming water pressure, we took a trip down to Lowes to buy the right tank. It was only about $50 and was pretty light, so no problems there. Now, the fun part! The steps for installation are fairly straightforward, as far as DIY projects go:
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Shut off water and water heater
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Drain water from pipes
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Release excess air from expansion tank
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Remove existing expander
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Prep. new expander
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Install new expander
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Turn water on and purge
1. Shut off water and water heater
Go find your incoming water supply and turn the valve off completely. The best way to find this is to trace the pipe marked as “Supply” back from your water heater. It’s important to turn the water heater down to a low heat (vacation setting) or off completely while you’re performing this work. No point in risking an injury.
2. Drain water from pipes
I’m assuming you don’t want a minor flood in your basement or utility closet. Unless you enjoy that sort of thing. Go open the faucet that’s farthest away from your water heater until water stops coming out.
3. Release excess air from expansion tank
Using an air hose attachment or a cheap-o tire pressure gauge, depress the valve at the bottom of the expansion tank. Oh, don’t forget a bucket! Remember, there’s water in that tank. If there isn’t water, you don’t need to do this!
4. Remove existing expander
Get ready for a fight. This step took me the longest by far. You’ll need two pipe wrenches and quite a bit of elbow grease. I recommend running a razor knife or painter’s tool along the threads to help loosen any gunk that may have built up over time. With a little brute force, you’ll have it loosened in no time. When you’ve almost got the tank off, get into a position where you can hold the tank effectively, as by this point it is likely full of water. You definitely don’t want to drop it.
5. Prep. new expander
The tanks come pre-charged to a certain PSI (check the label), so if you’re water pressure is within 5 psi of that, you can skip adjusting the air pressure. Otherwise, hook up an air compressor and pressurize it to within 2–5 psi of the water pressure. Of course, if you’re water pressure is lower than the pre-charge, you’ll need to release a bit of air. I also recommend using PTFE tape or plumber’s putty around the threads to ensure a tight, leakless seal.
6. Install new expander
Pretty self-explanatory, just tighten the tank into the T-fitting clockwise. Make sure you use the pipe wrenches on the hex fittings to get a tight seal.
7. Turn water on and purge
Now to test your handiness! Go turn the water on slowly and check for leaks. If you’ve done a good job you can continue to open the valve until you’re back to normal. Let the faucet that is farthest away from the water heater run for a few minutes to get out any excess air and you’re back in business.
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