I'm having problems with what I think is water hammer and finding where to start is a nightmare , I have 2 stop cocks for some reason! I live in 3bed semi 1940s where you had coal shed and toilet outside at some point a conservatory was added and toilet fitted out with the combi boiler and washing machine laundry room. One stop cock (stop1)comes down the side of the house into the kitchen and supplies kitchen sink dishwasher bathroom toilet and cold taps in bathroom. The other stop cock (stop2)feeds boiler the downstairs toilet and sink and washing machine. So I only get what I think is water hammer when stop2 taps and washing machine turn off the noise always comes from the bathroom .i.e when the washing machine valve shuts it sounds in the bathroom where the end of line is basically, could it be something simple like loose pipe.