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Plumbing CROSS CONNECTIONS - Health Risks from Plumbing Cross Connections

Any physical connection or arrangement between potable water and any source of contamination. A cross connection risks contamination of building water piping or municipal water supply with bacteria.

Common examples of cross connections in buildings include water softeners (see HEALTH RISKS & WATER SOFTENERS), washing machines, and dishwashers connected to a building drain without an air gap and water powered backup sump pump systems that use municipal water pressure and a venturi to evacuate water from a building or its sump pit (see Sump Pump Types).

Bathroom fixture cross connections

Older bath sinks and bath tubs (photo at left) may also form a cross connection if the tub spout is below the flood rim of the fixture. In our photo at left the original tub spout is below the top edge of the bath tub (the fixture flood rim). (A newer water spout has been installed through the tile tub surround wall.)

Clothes Washer Plumbing Cross Connection leads to Sewage Backup into Washing Machine

It's not just technical theory. Sewage backups into appliances do occur. One of our clients in Cold Spring NY awoke at 2AM to hear their basement clothes washer running unattended.

A washing machine drain hose in our photo (left) had been connected directly to the sewer line without an air gap. We pointed out the cross connection and risk of sewage backup into the washing machine, potentially providing a path of bacterial contamination back throug the washing machine into the house water supply piping.

Our client thought that the risk of sewage backup into the washing machine was not a concern. The new homeowner called us two weeks later with an amazing house noise and sewage backup story.

The home occupants woke at 2: AM, hearing a noise in their basement. Walking downstairs into the basement the occupants found that mysteriously the clothes washing machine had begun to agitate. This was an old washing machine that would start agitating when a sensor determined that the liquid level in the washer had reached a sufficient level.

During the night a municipal sewer backup had occurred in the street, forcing raw sewage back into the house sewer line, and upwards into the tightly-connected washing machine hose, filling the washing machine with sewage. The washing machine had been cross-connected by a tight plumbing connection to the building main drain line.

A sewer line backup had pushed waste into the washer where its pressure switch started the agitator. Plumbing cross connections are unsanitary and is a health risk. The clothes washer was merrily agitating away its full load, not of laundry, but of sewage.

Leaving a garden hose outlet end in an unsanitary water source such as a garden pond is also a cross connection that may be unsanitary.

Water Softener Cross Connections Between Drains and Water Supply Piping

Plumbing cross Connections such as those we show in our water softener backwash/recharge drain tube connections at page top and just at left deserve a mention while we're discussing water softeners. A "cross connection" is a direct physical connection between a building water supply pipe and a drain pipe.

This may sound like an unlikely event in buildings but in fact it is common in a few instances: installers often make a tight connection between the water softener backwash/discharge drain (usually a small diameter plastic tube) and a building drain. While it is not unique to water softener installations, this plumbing error is often made when these devices are installed. It is unsanitary and is a health risk.

What's the problem? In the unlikely event of a sewer line backup, sewage may be forced backwards up the drain and into the supply fixture, in this case the water softener - a very unsanitary event. There is also a possible bacterial growth path up such drains even when a sewer backup is not occurring.

Sump Pump Plumbing Cross Connections

Cross connections are defined with further examples at Home Inspection Definitions & Terms.

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WHAT CAN GO INTO TOILETS & DRAINS?
  DETECT HARD WATER
  MEASURE WATER HARDNESS
  HOW SOFTENERS WORK
  HEALTH RISKS & WATER SOFTENERS
  SALT OR WATER INTO SEPTIC
  REDUCE IMPACT OF SOFTENER
  SOFTENER ADJUSTMENT & CLEANING
  OTHER SOFTENER METHODS
  Winterize Water Softener & Treatment Equip
  Restoring Water Softener & Treatment Equip

• North Dakota Standards for Water Softeners, North Dakota General Authority Law, Chapter 62-04-08, Water Softener Units http://www.legis.nd.gov/information/acdata/pdf/62-04-08.pdf. "The objective of this chapter is to provide a standard of quality, capacity, and performance for water softener units. Water softener performance is to be based upon referee tests procedures described in section 62-04-08-09."
• Culligan Mark 10 Water Softener 1994-1998 Installation and Operating Instructions (covering models manufactured after 1995) (1-96) 01881948.pdf available from www.culligan.com
• Water Softeners, CMHC, Canadian Mortgage and Housing Corporation, cmhc-schl.gc.ca/en/co/maho/wawa/wawa_005.cfm - October 2008. Canada Mortgage and Housing Corporation acknowledges the contribution of Health Canada to the development of this document. For further questions regarding water treatment and water quality, contact Health Canada at watereau@hc-sc.gc.ca or call 613-957-2991 or 1-866-225-0709.
• "Commercial Water Softener Installation and Operating Instructions", IBC Filtration & Water Treatment Products (Australia) for commercial, industrial and residential application www.ibcwater.com.au (07) 3219 2233
• "Non electric water softener, Installation and Operating Instructions", IBC Filtration & Water Treatment Products (Australia), op.cit.
• "Water Softener Twin Tank Installation and Operating Instructions", IBC Filtration & Water Treatment Products (Australia), op.cit.
• Our Water Hardness Table used at originated with but was edited and added to from http://www.bestfish.com/tips/110598.html and also from www.water-research.net/hardness.htm
  

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