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Old 09-23-2010, 07:02 PM   #1
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Expansion tank - hot water heating system

The pressure on my hot water heating system is going too high and the release valve on the radiator keeps exhausting water. I have been told it is probably water in the expansion tank which has recently been installed to replace an old one. At the bottom of the tank is a small valve which I believe is to be used to exhaust the water. Any advice..


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Old 09-23-2010, 07:43 PM   #2
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I have an expansion tank with a similar valve. Once a year I drain the tank by opening the valve and allowing the water to flow out into a bucket. On some systems, there is an air inlet valve on the boiler that allows air to flow into the expansion tank, which allows you to drain it more quickly. By the way, you need to shut the valve from the boiler to the tank when you do this, else water from the boiler will fill the tank, which is supposed to be full of air.


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Old 09-23-2010, 07:45 PM   #3
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Does the expansion tank sit above or below the pipe it is attached to? Does the expansion tank have valves at both ends?

You want to get all the water out of the expansion
tank for starters. How this is done varies with the brand of tank.

Some tanks have a valve that requires an air hose similar to that used to pump up a car or bike tire, and which may or may not release water when opened. Pressure tanks with valves at both ends are easiest to empty out and to verify that the water is indeed emptied out.
The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.

Last edited by AllanJ; 09-23-2010 at 07:52 PM.
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Old 09-24-2010, 05:39 AM   #4
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If it's a bladder type tank, and it probably is, leave it alone. If the pressure is climbing on the boiler it is probably a bad fast fill valve or if you have a tankless coil, a hole in the coil.
Always ask to see your contractors license!
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