A loud noise coming from the pipes? To remove the water hammer, turn off the main water supply valve, open the tap located at the highest point in your home and turn on the tap on the lowest level.
This should drain all the water from the pipes and replace it with air. Once all the water has drained out the pipes, shut off the tap downstairs and turn the main valve back on. The air will be pushed out the horizontal and vertical pipes and out the taps by the force of the water.
This eliminates the water hammer. Using the radiator key to 'bleed out' the radiator through the vent on top can also help eliminate the water hammer. Call us if it doesn't work.