RESEARCH QUESTION: No sooner had the Travel section compiled a checklist of ways to protect your home before you go away ("Prepping Your Home for Vacation," July 24) than a leak sprang in our advice. Or so it seemed when a reader questioned our recommendation, based on interviews with water officials, to not turn off the water where it enters the house because of potential damage to the hot water heater.

The reader cited the Loudoun County Sanitation Authority as one source suggesting that the main shutoff valve should be, well, shut off. Now, with frozen-pipe season fast approaching, we wondered: What is the best advice?

METHODOLOGY: We interviewed old and new sources, both utility officials and professional plumbers. We asked them what they would advise their customers to do and what they themselves do to their homes when they go on vacation, regardless of the season.

RESULTS: Guess what? There is no conventional wisdom. But there is lots of information to help you decide for yourself what to do.

Fairfax Water, while warning not to turn off all the water to the house, did suggest turning off valves to toilets because leaks there often go undetected. That's still the biggest potential nightmare any way you look at it, according to our sources. It's also worth repeating that icemakers should be turned to the "off" setting to prevent leaks or overflow. Als, the hot water heaters should be turned to the "low" or "vacation" setting to save money, and furnaces turned down, but never below 50 degrees in either case or pipes could freeze. Otherwise, the same procedures can be followed year-round.

The Loudoun County Sanitation Authority, on its Web page "Your Household Plumbing" (www.lcsa.org/water/plumbing/default.cfm?pl1=6), does point to the main shutoff valve as one that "can be turned off while the property is vacant to prevent water damage that unforeseen leaks might cause." It also, like many plumbing specialists, recommends insulating pipes in unheated spaces within the house -- such as attics and crawl spaces -- to keep them from bursting in cold weather. The authority's primary concern is delivering water, however, not giving advice, says spokeswoman Samantha Villegas. "I'm sure there's an argument for doing it both ways," she says.

At the D.C. Water and Sewer Authority, engineers offer no hard-and-fast recommendations. "It would be a good idea to turn off the service line that's inside the basement," says spokeswoman Aleizha Batson. "Then, if something breaks, you're only dealing with the water contained in the lines. If you're worried about it, I would just have someone check on your home."

Al Richardson, spokesman for the Washington Suburban Sanitary Commission, which serves Montgomery and Prince George's counties, says turning off the water to the house entirely can prevent both leaks and tampering. "I've even heard of people removing the knob of a spigot." Many people don't know where the main valve is, Richardson says, which is why the valve should be tagged. "It's much easier just to turn the main one off so you haven't missed one." As for water evaporating from a hot water tank, "I would think that there's minimal, if any, evaporation" because the water vapor "has nowhere to go."

Cropp-Metcalfe plumbing operations manager Ben Kelley stands by the principle of stopping the water at its source. "The only way you're truly going to protect yourself from any leak at all is to turn off the water at the main valve. That way you can't have any leak at all. Or if you did, it would be limited to just what's in the pipes." Perhaps it's overkill to turn the water off at its source, but he's seen wood floors, drywall and plaster destroyed by leaks from stuck toilet valves that keep the water running. "It's the universal solvent."

As for damage to a hot water heater, "unless you're talking about being gone for a year, that's not going to happen," Kelley says. Water heaters stay full as long as water's flowing to them, and they typically hold 50 gallons, which is a lot to evaporate.

CONCLUSION: As demonstrated above, there is none. But interestingly, our sources' own habits reinforced the number one piece of advice offered to us on protecting your home: Have someone keep an eye on it. Here's what the experts do when they go away:

Villegas: "I don't even take vacations, so I wouldn't know." Hypothetically, though, she'd focus first on turning off the water to the washing machine and shutting down any outside spigots before the first frost to prevent a burst pipe.

Richardson: With two daughters, "there's always someone here." Because the key valves are tagged, "they can go and turn them off if something happens."

Kelley: "I don't think about it" because he has somebody who comes in to feed his Rottweiler.

-- Margaret Roth