We used to have a separate toilet next to the bathroom. When we have the loft extension built the WC was relocated to the bathroom to make way for the new staircase. Since then we have very low pressure supply in the washbasin cold water tap. Every time we use and flush the toilet, there is hardly any water from the cold water tap to wash the hand. I suspect the plumber who relocated the WC might have connected the feed for the cold water tap to the lavatory cistern as well. Is it right to do this or should the plumber have provided a separate feed for the lavatory cistern from the tank in the loft? Can anybody advise what's the remedial work required now to sort this out. Please help!