heating system repair

My home is heated through radiators by a gas-fired hot water boiler. The system has lost pressure, and my upstair radiators won't get hot. Normally the boiler's pressure gauge reads about 20 or 22 psi, and now it is reading less than ten. I tried emptying the expansion tank, and it filled maybe half way when I opened the valve, but that didn't do anything for the pressure loss. The pump seems to be working OK. Any suggestions? We're getting cold!
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On 10 Dec 2005 17:29:15 -0800, " snipped-for-privacy@starpower.net"

Yeah ya dork. Get out the yellow pages and call in a heating company or sit there like a deer caught in the headlights and freeze your ass off because if you cant figure out that problem then you dont need to be messing with it. Bubba
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Let the boiler cool and open the feed valve and fill to your cold normal pressure, the boiler not the expansion tank. Do you know what that is and what your cold pressure should be? then bleed the radiators. But as Bubba pointed out, if you didnt know this then you might mess it up, because this is the second thing you normaly learn after setting the thermostat at 70
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If you think about it, if you are opening the system (such as you "emptying" the expansion tank), you are going to LOWER the pressure, not raise it. If the expansion tank needed to be emptied, the pressure would be too high and also blow off out the relief valve. It sounds like it is not getting enough water into the system (bad water feed?).You REALLY need to call someone in that knows what they are doing...
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