[RyanD]

If I shut off the main water valve will that shut off the hot water too? The reason I'm asking is I was looking over the boiler system last night and I noticed that the water comes in from the cold water pipe into the tank. Pipes then come from the boiler(to heat it up I guess) and then a pipe comes out with the hot water into the house system. The off things [to me] was there was no shut off valve so it got me think if it can be shut off. Does the hot water pressure come from the same source as the cold?

 

[Scuba_Dave]

The main valve coming into the house should shut off all water
In some cases they are so old they need to be replaced as theyw ill not shut off the water

Sounds like your boiler also provides hot water
So shutting off any input to the boiler will shut off hot water
My boiler has a separate shut off valve, I do not need to shut off all water to the house

 

[RyanD]

The main valve coming into the house should shut off all water
In some cases they are so old they need to be replaced as theyw ill not shut off the water

Sounds like your boiler also provides hot water
So shutting off any input to the boiler will shut off hot water
My boiler has a separate shut off valve, I do not need to shut off all water to the house

So even if there is water in the tank it wont flow of the main valve is off?

 

[Maintenance 6]

If you have a boiler to heat your domestic water, shutting off the main water supply (cold) will also shut off the supply to the boiler, essentially shutting off the hot water too. You said it has a tank. It is possible to have a domestic water storage tank, but it more likely that the tank is the expansion tank for the heating water loop. That tank will still have boiler pressure even with the supply turned off. That is normally a small tank strapped above the boiler with a drain cock and a single pipe going into the bottom of it. Don't open that drain while the water supply is shut off. The water that circulates to provide space heating is separate from your domestic hot water.

 

[RyanD]

The tank I'm talking about is about 4.5' tall and about 2.5-3' wide. A big blue water tank next to the boiler.

 

[Scuba_Dave]

So even if there is water in the tank it wont flow of the main valve is off?

Correct - water is fed thru the pipes by pressure
Most house have between 35-80 psi
Once the water is shut off the pressure will drop - after a vlave is opened to remove remaining pressure in the lines

The exclusion to this is if you have a supply that is LOWER then the boiler
I have never seen this - except for the valves that are used to drain the boiler
If you do drain the boiler make sure the power is off 1st
You don't want it to kick on & try heating air