Boiler Expansion Tank Replacement in Boston
Relief valve dripping, or the pressure gauge jumping when the heat comes on? Call (617) 691-5446 to be connected with an independent local heating company that replaces boiler expansion tanks in Boston.
Service overview
What an expansion tank does
Water expands as a hot-water boiler heats up. The expansion tank gives it somewhere to go. Modern tanks have an air cushion behind a rubber diaphragm; older systems may have a steel tank hung near the basement ceiling. When the diaphragm fails or the old tank fills with water, there's nowhere for the expanding water to go, so the pressure climbs until the relief valve opens and drips. Replacing the tank, set to the right air charge for the system, usually solves it. Steam boilers don't use expansion tanks. For other boiler problems, see boiler repair in Boston.
! Common warning signs
Relief valve dripping or discharging
A relief valve that drips when the boiler is hot is often a sign the expansion tank has failed and the pressure is reaching the valve's limit.
Pressure swings when hot
If the gauge reads normal when cold but jumps high once the heat runs, the tank probably isn't absorbing the expansion.
Waterlogged tank
A diaphragm tank that feels heavy and sounds full of water when tapped, or water at the tank's air valve, means the diaphragm has failed.
Scope of work
What expansion tank replacement usually includes
A typical job covers confirming the tank has failed, replacing it, and setting the system pressure. Ask the company to price anything extra first.
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01
Confirming the cause
The technician checks the cold and hot pressure and the tank's air charge, and rules out a failing pressure-reducing valve.
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02
Isolating and draining
The system is isolated and partly drained so the old tank can come off without emptying the whole system.
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03
New tank and air charge
A correctly sized tank is fitted and its air charge set to match the system's fill pressure.
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04
Refill and test
Ask the technician to refill, bleed air, run the boiler and confirm the pressure stays in range when hot.
Why not ignore a dripping valve
A relief valve that keeps opening wears out, and a boiler repeatedly hitting its pressure limit is under strain.
Call nowTools used on an expansion tank job
Tire-type pressure gauge
Checks the air charge in the tank at the valve on its end.
Boiler pressure gauge
Shows the system pressure cold and hot, which is how a failed tank shows up.
Hand air pump
Sets the new tank's air charge to match the system fill pressure.
Pipe wrenches and sealant
Used to remove the old tank and seal the new one onto its fitting.
Local service
Expansion tanks are a common wear item on hot-water boilers in Boston homes. A failed tank often shows up as a dripping relief valve or water on the floor near the boiler. If water is coming from elsewhere, see boiler leak repair. If the boiler is old and has several problems at once, it may be worth pricing a replacement.
Expansion tank replacement in Boston
- • Downtown Boston
- • Dorchester
- • Jamaica Plain
- • South Boston
Example jobs
Relief valve discharging
If water is pouring, turn it off
If the relief valve is discharging steadily, turn the boiler off and keep people away from the hot water. Call (617) 691-5446 to be connected with a local heating company.
How expansion tank replacement works
Call and describe
Tell the company what the pressure gauge reads cold and hot, and whether the relief valve is dripping.
On-site check
The technician checks the tank, the air charge and the pressure-reducing valve to confirm the cause.
Replace and test
They quote the job, fit and set the new tank, and test the pressure. Ask for the quote in writing first.
What expansion tank replacement costs in Boston
It depends on the tank size, how it's piped, and whether other parts such as the relief valve or pressure-reducing valve also need replacing. We don't set prices; the company you're connected with quotes the work.
Tank size and type
Larger systems need larger tanks; converting an old ceiling tank takes more work.
Other valves
A worn relief valve or pressure-reducing valve may be replaced at the same time.
Time of the call
Scheduled visits usually cost less than after-hours calls.
Expansion tank questions, answered
How do I know my expansion tank has failed?
Common signs are a relief valve that drips when the boiler is hot, pressure that climbs a lot as the system heats, and a tank that sounds full of water when tapped.
Does a steam boiler have an expansion tank?
No. Expansion tanks are used on hot-water (hydronic) systems. Steam boilers work differently and don't need one.
Can I recharge an expansion tank myself?
Setting the air charge needs the system isolated and the pressure relieved, and a failed diaphragm can't be fixed by adding air. It's best left to a technician.
Why is my boiler relief valve dripping?
Often a failed expansion tank or a pressure-reducing valve letting too much water in. A relief valve can also wear out. Have the cause checked rather than capping the valve.