You may need to take a large amount of water out of the system. Too make sure that the Filler valve (mains top up) is fully shut ( it may be letting by due to faulty valve seat or dirt) you may need to issolate the mains comming into your property. There may be a valve before the filler loop that you could issolate.
You then need to switch off all power to your boiler/heating system. Drain the system from a suitable point. Should be a fitting either on a radiator pipework or near the boiler. If not issolate a small radiator ( both sides off the Radiator valves). There will be water in it so open the air vent and slowly drain it first be lossening a radiator fitting, you can carefully drain the radiator. When empty , tighten the fitting and open up valves again. This may be enough water to drop pressure down to around 1.5 Bar. If not repeat draining procedure. If you feel confident you could remove the radiator completely and use one of the valves to drain the system quicker. Kepping an eye on the pressure gauge at all times. When you have reached ideally 1.5Bar reopen the propery mains valve and any other valves one by one and see if the pressure remains constant.
Nik
May 2010
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