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Question DetailsAsked on 9/16/2014

how much should a boiler furnace expansion tank cost (parts and labor)?

I was quoted something like $1,000 for the expansion tank + some other parts + labor. There's some kind of issue with the boiler not quite reaching the right pressure. The actual furnace itself was apparently ok. Is this normal?

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1 Answer


$1000 - that is terribly, if not criminally, high, for a normal system, unless the "other parts include things like circulating pump or such. Get clarification on why so high, or more bids.

I am assuming you have a steam boiler or hydronic (baseboard or embedded hot water piping) heating system. The expansion tank takes up the slack, so to say, when the boiler kicks on and heats the water up to shutoff temp - does this by compressing a diaphragm against the air in the expansion tank, which then rerexpands as the water in the system cools off during circulation - or until next heating demand cycle, depending on how boiler is wired to operate (constant temperature or on-demand heating only). Typically control valve is connected to the tank and the incoming water piping and out to the boiler, but sometimes some are installed separately. The inlet control valve regulates the inflow of water into the system if the pressure in the heating system drops below a certain level. This provides makeup water to the system to maintain a minimum pressure - say about 15-20 psi typically for hydronic systems, steam systems can very a lot by age and manufacturer. It lets cold water in to replace any lost to leaks or as vapor released through air vents, or if the system is opened up or drained for repairs or for annual boiler flushing and such.

Here are a few related questions with answers, including info on typical cost. In your case, since you have a system pressure issue, you probably need the pressure control valve that goes on the bottom of the tank as well as the tank - materials cost typically about $70-100, installation cost same as for tank alone as noted in links below. Note the below responses may relate to water heater rather than boiler, but cost is very similar even though pressure on the system and tank is different, and water heater uses tank only normally, not an inlet control valve.

Answered 6 years ago by LCD

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