Hi guys I'm hoping someone here can possibly help me with an issue I'm having. I have a central boiler classic edge 550. On the backside of it there is a "sight gauge" that you can turn a small nozzle to check your water level. When I do this nothing comes out into the sight gauge water wise. The system also showed lo water so I tried refilling the tank according to the manual thinking this may also be the cause for no water on the sight gauge and I had a leak. However even after filling the tank with water, no water will show in the sight gauge despite the boiler getting so full the water starts pouring out the top of the boiler. Any ideas?