Dishwasher Gives Whole House The Shakes

Q: When my dishwasher draws water, it makes a terrible vibration and rattles the plumbing throughout the whole house. It frequently ends with a violent slap. I can relieve the noise by opening the hot water tap while it is drawing water, but the problem begins anew at the next cycle.

A: Start by replacing the solenoid valve in the dishwasher. These can set up a vibration in the line if they're not operating correctly.

If this doesn't solve the problem, high water pressure can be contributing, and ineffective or missing air chambers could be contributing. Air chambers in the plumbing lines absorb the shock of the abrupt closing of the line; the slap you hear is called water hammer. I would consult a plumber unless you are comfortable installing a pressure-reducing valve or air chamber.

Loose pipes rattling is another possibility that is easily remedied if you have an accessible crawlspace.

Q: I heard about a silent bathroom exhaust fan. I want one. Where do I get one?

A: To my knowledge there is no fan that is completely quiet. Manufacturers make very good quality fans that have low sone ratings (a measure of the noise output). Many are marketed as "quiet fans," however I have yet to see (or rather, not hear) one that is completely silent.

As with most things, you get what you pay for. Most of us have the $20 fans that are LOUD and don't move a lot of air. When comparing fans, check the CFM (cubic feet per minute of air moved) and the sone rating to find the one that best does the job you want. I'm still waiting for a silent dishwasher, myself. A foreign manufacturer makes an almost-silent dishwasher today, however I scream at the $2,000 check it takes to get one.

-- Stinky hot water: A gentleman with a Ph.D. in biochemistry suggested high-temperature bacteria as a possible culprit for the stinky hot water problem in last week's column. Flushing and dumping a gallon of bleach in the tank for 24 hours was the suggested fix. Others' theories included hydrogen sulfide produced by the aluminum-heating elements corroding and reacting with background sulfur in the water. One guy used to make stink bombs this way as a kid. I never did anything that cool!

-- Zinc strips: My question to readers about whether roof zinc strips could leach metals into creeks and kill fish led a Consulting Exploration Geologist to respond that as long as the water goes through some soil it is not a problem as "the organics in lower A horizon soils have an incredible ability to absorb metal cations." Yeah, I knew that. Thanks, Mr. Downes.

-- Indoor rain: I have been overwhelmed with correspondence from people regarding the unvented roof system in last week's column that was creating interior rain when it wasn't raining outside.

Many builders, architects and engineers have not experienced this phenomenon, as I had suspected. Many thought I was cuckoo for even suggesting it. Others see it repeatedly, as I have.

One thing not discussed in the column was the fact that many builders doing stressed skin panels, some log, cedar homes and other types of "closed" systems have been building them successfully for years. The key is that the entire envelope must be built to extreme levels of airtightness, as a thermos is, for example. Each joint in the rigid insulation is sealed to prevent moist air transfer and there is no cold-side air transfer whatsoever. This system will work if the methods are adhered to strictly. Problems occur when an inexperienced applicator uses elements of a closed system with elements of a conventional vented system.

-- Air gap: Two weeks ago, a reader asked about a leak at the sinktop air gap when the dishwasher ran. Before spending the money on a new air gap, it was pointed out I should have suggested first cleaning the hose from the air gap to the disposal (if so equipped). Debris in that short piece of hose can create backpressure and a leak.

-- Packing peanuts: Follow-up for the reader who wanted to put a large quantity of packing peanuts in his attic for added insulation (which I advised against): Owners of shipping stores told me they would be glad to take any amount of peanuts from the public to be reused. That sure beats the dumpster. Thank you everyone for all the great feedback, keep it up. Ask The Expert answers readers' questions every Saturday. Send questions to Ask The Expert, Seattle Times, P.O. Box 70, Seattle, WA 98111, or call 206-464-8514 to leave your questions on Ask The Expert's recorded line. E-mail address is dhay@seattletimes.com

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