Backflow Preventer Testing: What O'ahu Property Owners Must Know

Water in the public main normally flows one way: from the street into your building. Backflow is when that flow reverses. It happens in two ways. Back-siphonage occurs when pressure in the main drops, for example during a water main break or when a fire crew opens a hydrant nearby, and the drop pulls water out of your pipes toward the street. Backpressure occurs when pressure on your side rises above the main's pressure, as with a booster pump, a boiler or an elevated tank.

Either way, whatever is in your plumbing can end up in the neighborhood's drinking water. On an irrigation line that can mean fertilizer, pesticide and standing water from sprinkler heads. On a commercial property it can mean chemicals from a car wash, a dental office, a restaurant's soda system or a building's fire sprinkler loop. A backflow prevention assembly is a set of check valves, and on some models a relief valve, that closes the moment flow tries to reverse.

The catch is that it's a mechanical device with rubber seals, springs and moving parts. It can look perfectly fine from the outside while a fouled check valve quietly lets water through. The only way to know it works is to test it.

BWS runs a cross-connection control program that tracks thousands of privately and government-owned assemblies across the island. If an assembly is registered to your service, it's on the annual testing list. The most common properties with one include:

Commercial and industrial buildings, including hotels, restaurants, medical and dental offices, laundromats, car washes and anything with chemical processes. Condos and apartment buildings with booster pumps, fire sprinkler systems or a shared irrigation system. Homes and businesses with landscape irrigation, which is one of the most common assemblies on O'ahu, from Hawai'i Kai lawns to Mililani common areas. Properties with a private well, a non-potable water system or another water source tied into the plumbing.

If you've bought a property and aren't sure whether it has one, look near the water meter or where the main line enters the building for a brass or bronze body with two shutoff valves and small test cocks on the side. BWS can also tell you whether a device is on file for your account. If you're installing new irrigation systems on O'ahu, plan for a backflow device as part of the job.

Your due date is set from the date the assembly was installed, and it stays the same every year for the life of that device. BWS mails a first notice about 60 days before the due date. If no passing test report has been received by then, a second notice follows with an additional 30 days, and continued non-compliance can lead to further enforcement notices. You can read the program details on the Board of Water Supply testing program page.

Two points catch owners out. First, the customer, not BWS, is responsible for scheduling the test and paying for it, along with any maintenance the device needs. Second, the test has to be performed by a certified backflow prevention assembly tester and reported on the proper form. Simply opening a valve or eyeballing the device doesn't count. The easiest way to avoid a scramble is to book your test as soon as the first notice arrives instead of waiting for the second.

A standard test on a single device usually takes 15 to 30 minutes. The tester connects a calibrated differential pressure gauge to the test cocks, then closes the shutoff valves in a set sequence. Each check valve is checked to confirm it holds a minimum pressure differential, and on a reduced pressure (RP) assembly the relief valve is checked to confirm it opens when it should. The readings go on the test form along with the device's make, model, size and serial number.

Water is shut off to the property for part of that time, so for a restaurant or a hotel the test is best scheduled outside peak hours. Properties with several devices, such as a condo with separate assemblies for domestic water, fire service and irrigation, take longer, and it's worth testing them all on one visit so the due dates stay aligned.

O'ahu is hard on these devices. Salt air near the coast corrodes brass bodies, bolts and test cocks, especially on assemblies mounted outdoors in Kailua, Waimānalo, 'Ewa Beach and along the North Shore. Sand, grit and scale carried through irrigation lines lodge in check valve seats so they no longer close tightly. Strong sun breaks down rubber seals on exposed devices faster than on the mainland.

Other failures come from the property itself. A pressure surge from a stuck pump, a device that was installed backwards or below grade where it floods, or an assembly that was bypassed during an old repair all show up on test day. A failed test means the device isn't protecting the water supply, and it has to be serviced and pass a retest before the report goes to BWS. Catching a weak seal at the annual test is far cheaper than finding out after a contamination event or a missed compliance deadline.

The simplest routine is to keep a copy of every test report, note your due date somewhere you'll see it, and book the test when the first BWS notice shows up. For property managers juggling several buildings, a single annual visit that covers every device on site saves both downtime and missed deadlines.

Alpha Omega Plumbing has served homes and businesses across O'ahu since 2014, and our backflow testing and prevention service is built to take the hassle off your plate: we schedule around your business hours, explain the results in plain language, and get the paperwork to BWS. Call (808) 847-5414 to book your annual test or ask whether your property has a device on file.