FAQs

Why do water utilities issue boil water orders?

The Portland Water District invests millions of dollars each year to replace old water pipes and upgrade infrastructure, but unfortunately water mains still break. This presents a potential pathway for contaminants to enter the drinking water system.

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How does PWD know how much water our customers use?

We measure water use in hundred cubic feet, or HCF. One HCF is equal to 748 gallons. How much water is that? An average eight-person hot tub holds only about 500 gallons, so less than one HCF. It would take about 20 full bathtubs to equal 1 HCF.

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What is a cross connection?

A cross connection is a physical connection between the drinking water system and any other piping system containing a non-potable substance.

An example of a potential cross connection is a garden hose attached to an outside spigot with the end of the hose submerged in a pool or connected to a container holding a toxic chemical.

What is a backflow?

A backflow can occur when a substance flows back into the public water system as water pressure fluctuates.  This could be as a result of a water main break or hydrant usage.

How can you prevent backflows from occurring?

Backflows are prevented by installing backflow prevention assemblies onto a piping system to allow water to flow in only one direction. 

Do residential properties need backflow devices?

Yes, under the updated program, new residential construction or substantially renovated properties need to install backflow prevention devices.

Do you need to have annual testing of your backflow device?

Commercial devices are required to be tested annually and results filed with the Portland Water District. A list of certified backflow inspectors can be found on the PWD web site.  Non-testable backflow devices do not need to be tested. 

What are some examples of hazards at my home that could contaminate the drinking water system?

Irrigation systems, hose bibs, boilers, radiant heat systems, wells, docks, ponds, fountains, pressure boosting systems, pools, spas, graywater systems, rain water collection systems, reclaimed water, and solar heating systems are just a few examples of hazards that could contaminate the drinking water system.

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What is a backflow prevention device and which one is best to install?

Backflow prevention in a drinking water system is an in-line assembly that is used to keep undesirable water from entering the drinking water system during a backflow event. Your plumber will be able to assist you with the correct device for your system.  Generally, for residential water systems, a non-testable dual check valve assembly is adequate. 

DEVICE TYPE TABLE BASED ON WATER USE AND DEGREE OF HAZARD

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Does having a backflow preventer at my meter mean that my home/business is protected?

No. Having a backflow preventer installed at your meter only protects the public water system. There may be unprotected cross-connection issues within your property. Contact your plumber to discuss other preventative measures you can take to further protect your property from backflows. 

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Contact: 225 Douglass Street, PO Box 3553, Portland, ME 04104-3553

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