I had my boiler replaced recently and a filter was added to the system (Adey Prof2). The filter was positioned in the return pipe above the boiler. The filter makes a running water noise which is worst if the hot water circuit is on. (Y valve installation). Central heating circuit only is much quieter. This has driven me and the plumber mad trying to stop it. Today we removed the filter and replaced it with a small pipe. The noise stopped! So, can any one recommend a filter that will work properly in a vertical pipe where the water runs DOWN through it? Clearly the Adey was not a good choice. Thanks.