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I will need to close the main water shut off value to my house before starting work on kitchen plumbing. It is town water, and the main shut off value is just inside the foundation.

After the kitchen work is done, is any special procedure recommended for opening the main shut off value?

I am reading that a wave of high water pressure could cause damage to older plumbing when the main value is turned back on. Recommendations including slowly turning on the valve, and having faucets initially left open. Example: https://www.wsscwater.com/customer-service/report-problem/find-and-operate-your-main-water-valve

It is an old house, and some of the plumbing looks fragile. I have yet to find a consistent answer.

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    Sounds like you have the answer. Never a good idea to slam valves open or close. There will be air in the line/s so that is the reason to leave faucets open for a minute or two. Water pipes don't last forever, but hopefully we move before. If pipes have left 60 years behind them, might be an idea to start replacing a section of pipe every month or so.
    – crip659
    Aug 26, 2022 at 16:42
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    Imagining that you're turning the whole house off to work on the kitchen because there aren't separate shut offs. I would suggest that before turning the water back on, you install shut off valves (both hot & cold side) at every fixture in the house. This will simplify work in the future.
    – FreeMan
    Aug 26, 2022 at 18:12
  • @FreeMan - makes sense - but if you're doing a full remodel, you'd likely be working from further back than those individual shut-offs.
    – Tetsujin
    Aug 26, 2022 at 18:15
  • do not forget to air-vent the warm water heater
    – Traveler
    Aug 26, 2022 at 18:21
  • Can you provide more information on "air-vent the warm water heater". Would I do this with the water heater's temperature-pressure relief valve? What is the reason for this step?
    – john354
    Aug 26, 2022 at 19:18

2 Answers 2

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Apart from "how fast you open it" (slowly, but for the most part your plumbing should handle the pressure just fine) one good reason to have faucets open (and ideally, aerator screens removed) is that turning the water off and back on ends to disturb "crud" in the pipes.

Built up minerals, corrosion products, dirt that came in with the water supply over time and settled - and that "crud" will clog up small valve orifices and filter screens. If the faucets are wide open and the aerator screens are out, most of that crud will flush right out and cause no further problems. While living in an apartment on town water with copper pipes, I observed that any time the water system was shut down for work we could expect 3-5 minutes of brown, rusty-looking water when it was turned back on.

If your main shutoff valve is a gate valve, (handle takes several turns to open and close, and other identifying characteristics you can find by searching - common for older main shutoffs) be very cautious about not cranking on it too hard when opening and closing it. They have a nasty habit of breaking when operated after years of not being operated. 1/4 turn "ball valves" are much less trouble that way.

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  • I am seriously tempted to close my gate valve, install a ball valve, then open the gate valve and remove it's handle. Among other reasons, it's not hard to integrate ball valves into a smart-home system so leak detectors could automagically shut off the water.
    – keshlam
    May 24, 2023 at 0:29
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I'm not sure there's a 'best' way other than slowly.

If the water has a long way to climb, then you either close all the lower taps & let it climb first, or you just let it run until each tap starts to run, then close that one. Either way, water will eventually climb to the entire house.
What can happen either way is you get trapped areas, that will bang once full pressure has been restored if the tap is opened quickly - so, first time you open each tap after you think you're back to full pressure, open it very slowly, ready to close it down again if you feel an air gap, & let it run for a minute or two once any remaining air has flushed.

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  • Good advice, and don't forget the toilet tanks. In fact, it might be prudent to flush all the toilets just before turning the main supply back on, so that the tanks can fill under modest pressure and vent any air in their lines.
    – MTA
    Aug 26, 2022 at 19:12
  • @MTA - I'd forgotten about toilet tanks. I'd be inclined to leave them full, so you can gently open the ball valves to flush, rather than just let them run full tilt.
    – Tetsujin
    Aug 26, 2022 at 19:16

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