Cross Connections


Plumbing Cross Connections.

Plumbing cross connections occur where the authorities water supply comes into contact with a potential source of contamination.

Backflow from plumbing cross connections can cause contamination of the water supply.

Plumbing cross connections  are not in itself dangerous, and are an inevitable feature of modem plumbing and mechanical services systems. The concern, however, is back flow.

Problem of Cross Connections.

Cross Connections can endanger the quality of the potable water supply. When a disruption in supply pressure causes changes in system pressures a physical action known as back flow can occur.

A cross connection is any actual or potential connection between the potable supply and a source of contamination.

Back flow is the undesirable or unwanted reverse flow of liquids or gases in a piping system, and it can be caused by 2 physical conditions, Back-syphonage, & Back-pressure, or a combination of both.

Back syphonage occurs when the pressure in the drinking water system falls below atmospheric pressure. This is due to a vacuum or partial vacuum within the system. eg. broken mains, fire pump trucks withdrawing water, hoses left in tanks & Swimming pools, submerged inlets in tanks, undersized branch lines.

Back pressure occurs when the pressure in the non-potable system exceeds the pressure within the drinking water system. eg boilers, water heaters & pumps.

Plumbing cross connections can cause a flow of harzardous fluids into the drinking water supply

Cross Connection

Systems & premises where cross connections are prevalent.

Cross connections are prevalent in many applications where both potable and non-potable liquids are used in close proximity. It because the non-potable source may enter the potable supply that creates the hazard. The following industries use non-potable and potable liquids and because of this special consideration of cross connection consequences must be considered. -Hospitals, mortuaries, sewage treatment works, hairdressers, irrigation systems, abattoirs, automatic car washes, electroplating companies, commercial laundrys & dry cleaners, mobile pesticide spray units, marinas & wharf areas, reclaimed or recycled water supplies, farms with alternate water supplies, laboratory’s, radiator repair shops.

Examples of cross connections.

Hydro-aspirators in mortuary’s, flexible hoses left lying in chemical vats or pools, chemical or fertilizer injectors used in irrigation, hose taps located below ground level, dams interconnected with potable supply, domestic water heaters, commercial boilers & heat exchangers, toilet flushing apparatus and air conditioning cooling towers with
submerged inlets, reclaimed water pipes interconnected with the potable supply, steam & water heating devices, water powered or cooled mechanical equipment.

Hazard ratings

Cross connections have three levels of hazard.


Any condition which could cause death is classed as a high hazard rating because of the high risk.


Any condition or practice within the water supply system which could endanger health but not endanger life..


Any condition within the water supply system which would constitute a nuisance but not endanger health.

Control of Cross Connections.

The plumbing cross connection may be either eliminated, removed or controlled dependant upon the approval of the water authority.

Plumbers may control Cross connections by installing a back-flow prevention device, provided that this is acceptable to the water authority.

A physical air gap. Plumbers can provide an unobstructed vertical free fall distance between the water outlet and the spill or overflow level of the fixture. This the most common form of this.

Back-flow prevention devices.  Plumbers install mechanically operated valves known back-flow prevention devices on the upstream side of equipment where a cross connection may occur. These valves prevent water or liquid flowing in the reverse to that required.
If you have concerns regarding cross connections in your property,
call your local Newcastle Plumbers.
Wilmot Plumbers Newcastle
0432 428 532