I'm replacing a toilet shut-off valve (clean water flowing into tank) on the first floor of my (100-year old) home. I'm reading that I need to shut off the water, then drain the lines, before making the repair. This toilet is on the 1st floor of a 2 story home, with the water heater in the basement. For example, here it says:
Shut off the water at the main shutoff valve. If you have a gas water
heater, turn the knob to the 'pilot' position. Shut off the circuit
breakers to an electric water heater. Then open a faucet on the lowest
level of your house and another faucet on an upper level to drain the
pipes. Then disconnect the supply tube from the shutoff valve. Replace
the valve.
We have a gas water heater in the basement. My impression, though it may be wrong, is that if I shut off the water in the house, I also need to shut off the boiler such that it doesn't empty out and try to heat air, creating pressure and possibly an explosion. I could be wrong about this, and strangely enough I'm having trouble finding advice or readings.
My plan is to open the faucets on the floor below the floor with the toilet I'm changing in order to drain the system.
My question is: do I need to set the water heater to pilot, in order to avoid the dangerous scenario outlined above? Doing anything to our water heater makes me a bit nervous.
I've found a lot of advice on how to replace a toilet shut-off valve, but surprisingly little on this specific and incredibly common scenario.
Best Answer
NO, In the amount of time that it will take you change the valve there will be no issues with it set to the current temperature.
Once you turn the water off, even if someone opened a hot water faucet there would be no water pressure to push hot water out of the water heater (WH), so the WH will not need to fire up.
Once you turn off you main water supply you will want to open all the faucets in the house to bleed out what you can of water in the pipes to minimize the amount of water that come out of the toilet supply pipe when you remove the valve. You can turn it to the pilot setting if you want to feel more at ease, its easy and the pilot will stay on so no need to re-light it.
The boiler is a closed system, except for a one way valve that is designed to add water to the system if it runs low. It will not "empty out and run dry" if you shut of the main water supply for a short time. You can turn off the power to it if you feel you need to.