I fitted a Salamander CT50+Xtra pump for our shower just over 4 years ago and it has worked very well since. This morning, though, it is not pumping the water properly when I turn the shower on - it just makes a humming noise and the shower has lost all force. I have checked to see whether the input filters might be blocked, but they are not. Is there anything else I might check, or is it simply a case of replacing it at this point? There have been no changes elsewhere (hot water, etc) which could explain the problem as far as I can tell, it does seem to be something specific to the pump.