Derwood homes are generally on WSSC Water, and a house with in-ground irrigation has a testable backflow assembly that WSSC wants tested every year by a certified cross-connection technician. Dual check valves need a rebuild or replacement every five years. Call the number on this page to be connected with a local plumber in Derwood.
Derwood sits between Rockville and Gaithersburg near the Shady Grove Metro, and its housing is mostly from one decade: about two-thirds of homes were built in the 1980s. That matters for backflow, because sprinkler systems put in with the original landscaping are now decades old, and many of their devices have never been rebuilt. WSSC Water's program calls for testable assemblies, including irrigation pressure vacuum breakers and RPZs and residential fire sprinkler double checks, to be tested each year and after installation or repair, and for non-testable dual checks to be rebuilt or replaced every five years.
What to do now
- Find your device. On most Derwood lots it sits outside where the sprinkler line leaves the house.
- Check its age. Look for a date or a tag from the last test; if there is none, assume it is overdue.
- Turn off leaks. Close the irrigation shutoff inside the house if the device is spilling water.
- Get the right plumber. Ask for someone registered with WSSC who holds cross-connection technician certification.
- Bundle the five-year work. Have the dual check looked at during the same visit.
Symptoms and causes
| What happens | Usual reason |
|---|---|
| Relief port drips while zones run | First check or relief valve worn |
| Spray from the bonnet | Vacuum breaker seal failed |
| Weak pressure in one or two zones | Debris in a check or a valve left half closed |
| Body cracked after winter | Water trapped in the device during a freeze |
| Test fails year after year | Old assembly better replaced than rebuilt |
What changes the price
- A straight test versus a test with parts and a retest
- Rebuilding an original 1980s device versus replacing it
- RPZ versus pressure vacuum breaker
- A WSSC permit if the assembly is replaced or moved
- Extra devices such as a fire line or a pool fill
Before you book
Derwood is unincorporated, so there is no town permit layer: WSSC Water handles plumbing permits and Montgomery County handles building permits. If a device near Lake Needwood or the stream valleys sits in a low, damp spot, ask whether moving it to higher, drier ground would make future tests and winters easier. Spring start-up is the natural time for the yearly test, and booking a few weeks before the first mowing leaves room for a rebuild if the old device fails.
Backflow Testing questions in Derwood
Why does a lawn sprinkler system need a backflow preventer?
How often does a testable backflow assembly need a test here?
What happens if the assembly fails its test?
Will I get a reminder when a test is due?
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