Page 341 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch09_297-332.qxd 8/2/10 9:54 PM Page 301

9.2 Public Health Significance of Cross-Connections 301
9.2.3 Heating System Antifreeze in Potable Water

Bangor, Maine, Water Department employees discovered poisonous antifreeze in a home-
owner’s heating system and water supply. The incident occurred when they shut off the
service line to the home to make repairs. With the flow of water to the house cut off, pres-
sure in the lines in the house dropped and the antifreeze, placed in the heating system to pre-
vent freeze-up of an unused hot water heating system, drained out of the heating system into
house water lines and flowed out to the street (see Fig. 9.3). If it had not been noticed, it
would have entered the homeowner’s drinking water when the water pressure was restored.

9.2.4 Salt Water Pumped into Freshwater Line
A nationally known fast-food restaurant located in the southeastern United States com-
plained to the water department that all of their soft drinks were being rejected by their
customers as tasting “salty.” This included soda fountain beverages, coffee, orange juice,
etc. An investigation revealed that an adjacent water customer complained of salty water
occurring simultaneously with the restaurant incident. This second complaint came from
a waterfront ship repair facility that was also being served by the same water main
lateral. The investigation centered on the ship repair facility and revealed the following
(see Fig. 9.4):

• A backflow preventer that had been installed on the service line to the shipyard had
frozen and had been replaced with a spool piece sleeve.

Automobile antifreeze
added to boiler water
Backsiphonage
(reverse flow)

Normal flow
Curb stop with stop Water main
and waste drain
Figure 9.3 Heating System Anti-Freeze into Potable Water