Hydrant pressure can uproot rust, sediment

Q: A house caught fire a couple of blocks away from me, and while the firefighters were on scene and for several hours after, the tap water was filthy and rusty. Why does this occur?

A: When a fire hydrant is activated the very large amount of water flowing through the system tends to disturb and uproot the sediment and rust in the water main. This visually dirty water is then drawn into your home.

Water utilities routinely flush their systems using the hydrants or other inline valves to verify hydrant flow rates and check for valve leaks and proper operation. But more important, the flushing is done to protect the quality of the water, eliminate some of this rust and to check for what is called the "chlorine residual" in areas with low flow.

Public water systems are designed by regulation to provide 20 pounds of water pressure during a firefighting or flushing regime, preventing contamination from backflow.

Backflow-prevention devices at vulnerable use points in the home (valves at irrigation sprinklers and a dishwasher air gap being prime examples) further protect the system from contamination.

This regular water-line flushing is particularly necessary at dead-ends in the system, such as cul-de-sacs.

During a fire or system flushing, do not use hot water because the rusty water will be sucked into your hot water tank. Do not do laundry because the water might stain clothing.

Afterward, flush the system in your house with cold water and clean the faucet aerator screens if needed.

Q: Our home was built in the mid-1920s near the arboretum. For the past several years, we've been trying to subdue and get rid of hobo spiders in the basement. The basement is dry and is about 3/4 finished. The spiders are found most frequently in the finished living areas. Over the course of last year, we probably killed 12-18, mostly by using the flat sticky spider traps. Do you have any treatment or prevention ideas other than continuing to use the sticky traps?

A: The very common (in the Northwest) hobo spider is frequently confused with the brown recluse spider, not only visually, but also by the clinical symptoms a bite can bring.

Some of the symptoms are a lesion, nausea, weakness and a long-lasting headache that doesn't respond to pain relievers. Fortunately these bites are rare.

According to Washington State University, these spiders can move rapidly (15-20 inches a second) but do not bite unless provoked. Its natural predator is the giant house spider, so killing or trapping all spiders may not help your problem.

Do not use pesticides. Spiders are beneficial! Hobo spiders build their funnel-shaped webs in dark moist areas, such as crawlspaces or basements, and wait at the mouth of the tunnel for their prey.

Sealing potential points of entry around the perimeter of the home and at the roof line are your best preventive methods, followed by general cleanup of firewood, tall grass and garbage — places where they can nest and/or gain access.

Darrell Hay is a local home inspector and manages several rental properties.