This is the water from the tap connected to your house by the local authorities. You have no control over its quality even though there is a standard that they have to keep within.
There is usually a connection fee and this amount can be found usually on your planning permission or your Local Planning Department.
This fee has to be paid before you start anything.
Make sure that you have placed the right water pipes to the house at the initial stage of the construction as the water board would only connect you to the edge of the site. All the internal plumbing are your responsibility.