Turning off the water

[clonkel]

If I turn off the water at the stopcock in the house to work on the kitchen sink and lets say there is no isolation valve then how does turning of the water work. Sorry if it sounds like a dumb question. So if I have a cold mains feed which branches with one branch going to the kitchen sink and the other to sink B. When I open the kitchen sink cold tap does all the water have to drain from the other branch (the one going to sink B) or is it only the water in the kitchen sink branch that will drain as the other branch will be held by a vacum (I am thinking thumb over a pipe with water in it that when turned the water stays where it is).

Also, I have an unvented system what happens to the hot water? I believe that the water in the cylinder will come out by the force of the cold feed into the cylinder and this is turned off so does that mean that only the hot in the pipe from the cylinder to the kitchen sink tap will be drained?

Finally, do I need to open other taps apart from the kitchen sink if I am only working on the kitchen sink?


Thank you

 

[Aquarius]

Yes turning off your stopcock should isolate both hot and cold supplies for your setup. Depending on what work you’re doing, you might need to drain all other outlets, so bathroom for example. In answer to your question, it stops any more water coming in.

 

[clonkel]

Thank you.

 

[Timmy D]

Turn mains off.
Open hot and cold at highest outlet.
Open hot and cold at lowest outlet.
System will drain.
Commence work.

 

[clonkel]

Thank you. The highest outlet is the upstairs bathroom sink the lowest is the kitchen sink/bath downstairs. The house is 2 floors so 'I guess' that would mean the outlet that I am working on (lets say utility room tap downstairs) + something upstairs

thanks again