Why should I *not* shut off the water to my house when I go on vacation?

August 26, 2023 2:01 PM

When I go on vacation, I usually shut off the water at the main valve outside my house to avoid disasters like pipe / hose bursts from ruining everything. (Those washer hoses - beware!) My dad noticed this one day, and told me that two separate plumbers had told him not to do this. But he didn't ask why. So now I'm stumped: why would you *not* want to shut off the water to your house when you go on vacation? (Aside from your plants suffering from lack of irrigation)
posted by Mushroom12345 to Home & Garden (17 answers total)

Best answer: Because if a main valve fails, it can be a major pain in the ass, because you’re gonna need the water utility to isolate it. Also, just shutting the main off doesn’t drain the system, so you still have water in it. Draining the water system can cause dirt and debris to get dislodged and can clog up sinks and other appliances that use water.
posted by HVACDC_Bag at 3:09 PM on August 26, 2023 [4 favorites]

Best answer: I shut my house water off all the time and I've tried to think through possible problems. One scenario I've seen mentioned is if your system develops a leak and the water heater is on, it may run while underfilled or even empty. So make sure the heater is also off?

I've also noticed that turning the house back on will sometimes send a shock of water pressure through the system if something does slightly drain the house like leaving an ice maker on (another thing to check). Plumbers will say that kind of stress on the pipes and valves can lead to trouble in older houses.

And that might be right. I did come back from vacation one year and the hot water heater was leaking the next morning. Coincidence? Perhaps. So be sure to turn it back on verrryyyy slowly. And expect air pockets in the line to cause your faucets to burp and splash for a bit.
posted by JoeZydeco at 3:41 PM on August 26, 2023 [3 favorites]

Draining the water system can cause dirt and debris to get dislodged and can clog up sinks and other appliances that use water.

This. Our 7-unit building has no per-unit valves so every time anyone has any significant plumbing work done we have to shut off the main, and invariably the water runs brown for a while afterward, drains often get slow, etc.
posted by staggernation at 4:54 PM on August 26, 2023

Best answer: Regarding main valve failure - I actually had this happen when we were buying our first house. The seller decided to "helpfully" turn off the water at the main valve after moving out. The next day, when we went in for final inspection, there was a pool of water in the basement (no major damage, fortunately) from the drip that had started at the main valve when he turned it off.

A plumber was able to just repack the valve stem without major repair, and it was fine for the next 12 years, but ... not a great first-time homebuyer experience.
posted by jferg at 5:33 PM on August 26, 2023 [3 favorites]

Best answer: The thing with the main valve is that the reason valves fail when you use them is not because they shouldn't be used, it's because if they are never used for many years, they are much more likely to fail when you do use them. You don't want to have an actual emergency that requires shutting off your main valve and find that it hasn't been moved in a decade and no longer works! So regularly opening and closing your main valve is good thing.
posted by ssg at 5:55 PM on August 26, 2023 [9 favorites]

Best answer: Maybe worth testing your main valve, but since it seems like you have, there's no reason to think it's any more likely to fail than any other valve in your system, right?

As for shocks to pressure. My 192X house exhibits a "water hammer" effect quite often when one sink is used, unless you know the trick of turning the faucet off decisively. This makes massive shocks in pressure but my old (mostly iron) pipes are fine. This is another thing you could in principle stress test.

The water heater point above is good. But I think you're good to turn it off at the main valve overall if you've done due diligence, though I will also be asking plumbers I know when I can!
posted by SaltySalticid at 6:01 PM on August 26, 2023

I wouldn’t do it on general principles. The system is working, you haven’t had any problems with it, so you make a big change to its operation mode and leave immediately. That doesn’t seem wise to me?
posted by Tell Me No Lies at 8:13 PM on August 26, 2023 [7 favorites]

I would never have thought to do this before. On the other hand, there was that one time when the wire mesh hose thing that goes from the wall to the toilet blew out at like 3 in the morning. And we figured it out pretty quickly, and it still did a fair amount of damage. A week of that would have been catastrophic amounts of damage.

So thanks for putting that new fear into my head...
posted by Windopaene at 8:56 PM on August 26, 2023 [1 favorite]

What is the probability or likelihood of an issue happening if you leave a working system as is and what is the probability of something happening when you put a change into the system? I guess a problem is better to have when you are home than no home, but any issue that arises from you shutting off the main seems like an unforced error. If you are concerned about your washer hoses, either replace them or turn off the water at the machine.
posted by JohnnyGunn at 9:10 PM on August 26, 2023 [3 favorites]

I shut off my water main when I travel. I also have water sensors under sinks and behind toilets connected to my monitoring alarm system.

My relative was was on vacation when their toilet supply line broke (it's a plastic connection to the tank) but thankfully their neighbor noticed after only a day of flooding and shut off the water main and contacted a flood-cleanup service. As a result I'm paranoid now about making my house "safe" when I travel.

The water main valve is new & healthy, and I use it often enough. I always turn the water back on slowly, as I have extra-high water pressure. I have a tankless water heater that I also turn off when I leave, so I'm not worried about a hot water tank. I turn off the fridge ice maker too.

My irrigation system is on a different water main valve, so I leave that running.

The only negative I can think of is that my outdoor water spigots are disabled when I'm away, and if for some reason somebody needed to use a hose at my house for something important (extinguishing a brush fire?) then they couldn't.
posted by jpeacock at 9:18 PM on August 26, 2023 [2 favorites]

My plumber did suggest shuttiing the valve where water enters the water heater.
posted by SemiSalt at 4:51 AM on August 27, 2023 [2 favorites]

I can't think of a reason not to if your shut-off works reliably.

I turn mine off every time I'm gone for more than a long weekend. I also turn off the hot water heater in case a leak exposes the heating elements. I don't bother draining the whole plumbing system each time. With the main shut-off a leak would have much less pressure and only leak as much water as is in the pipes above it, substantially limiting the damage compared to a leak with unlimited city water behind it (plus the cost of the water).

When I moved in we did have the 25 year old gate value replaced with a new ball valve so operating my shut-off is less sketchy than some.
posted by token-ring at 12:07 PM on August 27, 2023 [2 favorites]

There are other things in your house that may need a constant supply of water -- a water softener uses fresh water during its recharge cycle, and a whole-house humidifier may need water to avoid being damaged while enabled. If "shut off water" is on your vacation to-do list you may need to add a handful of other things like shutting off water-dependent automated systems, and then actually remember to do those too.
posted by AzraelBrown at 6:04 AM on August 28, 2023

Best answer: Another note about the water heater...

Shutting the main feed off creates a closed system. Water expands when it heats up. If for whatever reason the tank were to heat up too much, the tank's excess pressure would normally relieve itself through the cold inlet as the water "expanded" back towards the street. If you turn that valve off, the only thing protecting you from an explosion is the pressure relief valve on the tank.

You have tested the tank's pressure relief valve recently, right?
posted by RonButNotStupid at 6:24 AM on August 28, 2023

Response by poster: Based on the replies, I'm never leaving my home again - not even to go to the store. (joking)
posted by Mushroom12345 at 3:15 PM on August 28, 2023 [1 favorite]

My parents are religious water turn off-ers after having two water incidents. One was a sink on the top floor that flooded hot water all down the centre of the house for several days. It was extremely expensive to fix. The second was the line to the fridge ice maker.

I'd think even if turning it off caused a problem or leak, at least that would be at the bottom of the house.
posted by lookoutbelow at 4:02 PM on August 28, 2023

the tank's excess pressure would normally relieve itself through the cold inlet as the water "expanded" back towards the street

This depends on whether your water company/code/whatever mandates backflow preventers on the house connection to the water main. If one is installed, it doesn't matter if the valve is closed or not, water still can't flow back into the cold side. This is one of the reasons new plumbing systems are generally required to have a thermal expansion tank attached to the water heater's supply line these days.
posted by Aleyn at 5:34 PM on August 28, 2023 [1 favorite]