Just had a new monobloc tap fitted to my kitchen sink. My water runs direct from the mains, with the hot running through a combi boiler. The flow rate on the new tap is terrible. I tested it and got less than 4 litres per minute on cold, even less on hot. The old monobloc tap had really good flow, as do all my other taps around the house. The plumber fitter has been back to check his work, and says that everything is as it should be. The new tap is designed for high pressure systems, and I bought it from Wickes, who have said I should buy another tap and pay to have it fitted, and bring the old one back for a refund, all of which will leave me out of pocket. Can anyone suggest why this new tap might be so poor (it's a spirallly design with a pull out head).