Shutting the water off when you leave: is closing the main valve enough?

Sunday evening, before heading back to Montréal, you go down to the basement and close the main shut-off. It’s a good habit, and one often recommended when a house sits empty.

But a closed valve doesn’t put the house out of reach of water damage. It cuts how much water can run; it doesn’t empty the pipes, doesn’t stop freezing, and doesn’t always close as well as you think.

What to do on top of closing the valve

1. Find the right valve and label it

The main shut-off is usually where the water line comes into the house: in the basement, the crawl space or a utility closet. On a well, it’s often near the pressure tank. Put a clearly visible tag on it, for you and for anyone who has to find it in a hurry.

2. Close it, then make sure it holds

An old valve may no longer close all the way. To find out: close it, open a tap, and see whether the water stops once the pressure is gone. If you have a meter or a pressure gauge, write down the reading when you leave and compare it when you get back. A valve that lets water through or leaks at the stem gets replaced by a plumber.

3. Release the pressure

Once the valve is closed, briefly open a tap on the lowest level of the house, then close it. The pipes stay full, but without pressure; if a fitting gives, much less water comes out.

4. On a well, think about the pump

The pump can kick in if pressure drops in the part of the system before the valve. If its breaker is clearly labelled in the panel, switch it off when you leave. If nothing’s labelled, have an electrician or your plumber sort it out rather than flipping breakers at random.

5. Ask your plumber about the water heater and hot-water heating

A water heater stays full with the valve closed. A hot-water heating system (hydronic baseboards, radiant floor) may have its own supply. Some equipment, like a water treatment system, doesn’t cope well with the water being cut. Have a plumber who knows the setup sign off on your routine.

6. Leave the heat at the recommended setting

This is the part people forget. Water left in the pipes, the water heater, the traps and the toilets freezes just as easily with the valve closed as open. Heat is still the real protection against freezing, at the setting your plumber or insurer recommends.

Why the valve isn’t enough

What the valve does

It stops new water coming in. If a pipe splits while you’re away, what runs out is limited to the water already in the pipes and the water heater, instead of an endless supply from the municipal line or the well. That’s a big difference, and it’s why the habit is worth it.

What it doesn’t do

• It doesn’t drain the plumbing. Everything downstream stays full of water, and that water can freeze if the house cools.
• It doesn’t protect what’s upstream. The stretch of pipe between the foundation and the valve — and on a well, the tank and pump — stays under pressure.
• It doesn’t empty the water heater. A leaking tank empties onto the floor, valve closed or not.
• It doesn’t guarantee a tight seal. An old gate valve, scaled up or worn, can let a trickle through.

Townships realities

Many cottages are on a well. The system starts at the bottom of the well, not at the basement wall. The main valve only isolates part of it.

Valves are often old and awkwardly placed. In a cottage added onto over the years in Sutton or Potton, the valve may be at the back of a crawl space, behind boxes, or added somewhere inconvenient.

Heat sometimes stops with nobody around. A power outage on a wooded road, an empty propane tank: if the house cools, the closed valve doesn’t prevent freezing; it only limits the water that comes out at the thaw.

What you can do, and what belongs to a plumber

What an owner can do:

• Find, label and close the main shut-off when you leave.
• Release the pressure through a low tap.
• Write down the meter or gauge reading.
• Switch off the well pump if its breaker is clearly labelled.
• Keep the heat at the recommended setting.

What belongs to an RBQ-licensed contractor:

• Replacing a valve that’s stiff, leaks or won’t close fully.
• Adding a valve somewhere accessible.
• Installing an automatic shut-off valve tied to a leak sensor.
• Advising on the routine for your water heater, hot-water heating and well.
• Fully draining the plumbing if the cottage is closed and unheated.

Check a contractor’s licence in the Régie du bâtiment du Québec registry.

In an empty house, how long before anyone notices?

With the valve closed, a split pipe runs for less time. But a leaking water heater, water freezing in a trap or the section upstream of the valve aren’t dealt with, and nobody sees them.

How often someone stops by sets the maximum length of any damage. A meter or gauge reading at every visit also shows whether the valve is really holding. Many insurance policies mention shutting off the water when the house is left empty; conditions vary from one insurer to the next, so reread yours or ask your broker.

What we look at on a visit

Every visit, we read the thermostat, check that the main shut-off is in the position agreed with you, look at the incoming water line and its fittings, read and log the meter or pressure gauge with every tap closed, listen for the well pump starting on its own, and look at the water heater’s base and drain pan. Every finding is photographed and time-stamped in the report.

If something’s off, we call you the same day, with photos. If needed, we meet an RBQ-licensed plumber on site and document the work.