Here is a small selection of terms that are frequently used in the world of plumbing and as such it is really important that plumbers and inspectors know all terms and what the mean: Air Chambers are used to absorb pressure and stop water hammer. They are normall installed as close as possible to valves or taps and also at the end of long lengthes of pipework. Clapham Plumbers are professionals. Air Gap (Drainage System) refers to the vertical distance through the atmosphere between the outlet of a water pipe and the flood level rim of the receptacle into which it is discharging. Air Gap (Water Distribution System) refers to the vertical distance through the atmosphere between the lowest opening from any pipe or tap that supplies water to a tank, plumbing fixture, or other device and the flood level rim of the receptacle. An Air Lock is a bubble of air which restricts the flow of water in a pipe. Backflow refers to the flow of water or other liquids into the distribution pipework of a potable (drinking) water supply from any source or sources other than the intended source. Back siphonage is one type of backflow. A Clapham Plumber can supply and fit all types of plumbing appliances. Back Siphonage is the backward flow of contaminated, or polluted water from a plumbing fixture or vessel into a potable (drinking) water supply because of a negative pressure in the pipework. Building Drain is the part of the lowest pipework of a drainage system that takes the discharge from soil, waste, or other drainage pipework inside a building (home) and transfers it to the building sewer 3 feet away from the wall.?Cross Connection is a connection between two separate pipe systems, one of which contains potable (drinking) water and the other either water of unknown or questionable safety.