i have a Ferroli modena 80 .the problem is that the flow of hot water is very poor.also the pressure gauge rose to 3 bar but has come back down to 2 bar.heating and hot water work its just the flow of water is worse than it used to be.also one day dirty water came out when running a bath.the boiler is approx 3 years old.im not sure if the pump is working or how to check it.any ideas?

As its a young bolier I wouldnt have thought dirty water issues would be a duff heat exchanger - much more likely roadworks! Also I dont think the pump operates for hot water use - the water gets pushed through the heat exhanger by mains pressure alone.

Check for a sticky diverter valve (that 3 way thing with a lever that slides in/out when a tap is opened to divert water from rad system to the tap system).

That's an amateur start for you :)