Blocked Stack

[dave-air]

I have just purchased a house where we have removed the kitchen. We also removed the old sink waste pipe but now when the upstairs loo is flushed there is a surge of water from the kitchen stack connection.
Is this normal or is there a stack blockage? The stack is cast iron so no obvious rodding point.

 

[Softus]

Which do you consider to have the lesser resistance - several metres of soil pipe above- and underground, with bends and turns, or a 4" hole opening directly into a kitchen?

 

[dave-air]

Which do you consider to have the lesser resistance - several metres of soil pipe above- and underground, with bends and turns, or a 4" hole opening directly into a kitchen?

True, however, I would also consider that several metres of soil pipe to have the capacity to take 5 litres of water before a bend.

 

[Softus]

I would also consider that several metres of soil pipe to have the capacity to take 5 litres of water before a bend.

If that several metres of pipe is filled by a vacuum, i.e. is 'empty', then I might agree with you, but it isn't empty - it's full of air. We're talking about the rate at which air can be either pushed along the pipe and vented elsewhere, ahead of the water, or change places with the water and be vented at the same property. These things aren't as simple as you seem to think.