I had a pump (Stuart Turner Showermate 1.4 bar twin) installed on a new shower (with thermostatic valve) at the end of last year and it worked for a few months with no problems. For the last few months the pump cuts out after approximately 2 or 3 minutes; but the pump re-starts if the shower valve is turned to cold. After 15 or so minutes the pump works again (but cuts out again after 2 or 3 min). I've spoken to Stuart Turner and they think it's a problem with the hot water pressure in the system i.e. the cylinder is emptying faster than it is filled up from the cold water tank. This seems plausible given the fact that the pump works again after it has been left for a while (and the cylinder has filled up again) but why did it work for the first few months? Are there any other things that might have caused the hot water pressure to drop? Blockages in the pipe? Air in the pipes? The fact that I haven't been using my central heating over the summer? Are there any ways to increase the pressure coming from the cylinder? (I can't increase the height on the cold water tank). Is it possible to fit another pump from the cold water tank to the cylinder? Grateful for any advice.