Shut the water off at the main. If you do nothing else on this list, do that.
A supply line that fails in an occupied house is a bad afternoon. The same failure in a house nobody will enter for four months is a different category of problem entirely, and it is the single most expensive thing we get called to in this valley.
Before you leave
- Close the main shut-off. Know where it is before the day you leave. Usually at the street in a concrete box, sometimes on the side of the house near a hose bib.
- Open a low tap afterwards to take the pressure off the system and let the lines drain down a little.
- Turn off the water supply to the ice maker separately if it has its own valve. Ice-maker supply lines are a classic failure point and they are cheap plastic more often than they should be.
- Check under every sink for the beginning of a problem. A slightly damp cabinet floor in August is an emptied ceiling in November.
- Look at your washing machine hoses. If they are rubber and you cannot remember when they were fitted, replace them with braided stainless before you go. This is a twenty-minute job that prevents a genuinely catastrophic one.
- Pour water into floor drains and rarely-used traps. A dry trap is an open pipe to the sewer, and the smell that greets you in October is the mildest consequence.
The water heater question
If the water is off at the main, the heater is not being fed, and leaving a tank heater running for months to keep water hot for nobody is money burnt.
Most tanks have a vacation setting. Use it. On a gas unit that keeps the pilot lit without cycling the burner to full temperature; on electric, switch it off at the breaker.
Do not simply drain the tank and walk away unless you know what you are doing. A gas heater fired with an empty tank is destroyed in minutes, and the person who relights it in October may not be the person who drained it in May.
While you are away
The point of shutting the main is that most of what could go wrong now cannot. What is left is worth a set of eyes.
Have someone walk the house monthly — a neighbour, a property manager, whoever already has a key. What they are looking for takes two minutes: stains on ceilings, damp at the base of the water heater, anything wet that should not be.
If the house has a pool, an irrigation system, or anything else that stays live while the interior is shut down, those keep running on their own supply and want their own check.
Coming back
Open the main slowly. Not for any mystical reason — a fast refill slams air through the lines and can push debris into cartridges and aerators.
Then, in order: open a tap and let it run until it is clear and steady, walk the house and check under every sink and around the heater while the system is under pressure for the first time in months, and only then turn the heater back up.
Run the water long enough to clear what has been sitting in the lines before you drink it or fill anything with it. Standing water in a hot house for four months is not water you want in a glass.
If something is going to have failed, it declares itself in the first hour under pressure. That is the hour worth being present for.