Has anyone else got a TF1? I have one fitted on my central heating return pipe by the boiler, and it makes a sound when on (when boiler is not firing but pump is on overrun it more noticeable) - sounds like water velocity noise coming from it. I've bled it and some air comes out of the air vent but it still happens. Anyone else had this? It does a good job, when I cleaned it out, loads of crap was on ther magnetic rod, but it's quite noisy, water running sound, when on!