Can I replace water supply pipe without telling the water company?

[yellowcone]

our supply pipe from the water meter to stopcock in house is lead , want to replace by moling new plastic pipe under tarmac driveway with different route to other side of house . When I spoke to water company they said the communication pipe is copper and to change to plastic would be £5,000 but that if we change the supply pipe to plastic then we have to pay for them to replace the communication pipe ? Is this correct ? Plumbers seem to think there is a misunderstanding and that we can do what we want within our property boundary and the communication pipe is fine to stay as copper.
We would use a WIAPS approved contractor.
any ideas ? Thanks!

you are responsible for the piping after their meter.
End of discussion

Thanks !

They will need to turn the supply off for the whole street to reconnect you.

but OP wants to change the pipe after the meter, there is no need to "interfere" with the communication pipe owned by the water company which brings their water to the meter.

turn the meter off and you can do whatever you want on your side of it without needing to involve the water company.

As the OP alludes to, there has been some level of misunderstanding between OP's desires and water company's thoughts.
Water co has "confirmed" the communication pipe is copper, so need to do anything with it. OP however is convinced the supply pipe from meter to stopcock remains original lead and thus very much needs changing, which cost is entirely down to the customer, not the water co.

Yes, they can re-lay the service pipe but the water company will need to be making it connect in. The householder is can lay the pipe up to their boundary but if the external stop tap is located in the public footpath or highway then all the householder can do is leave enough tail of pipe to allow the water company to work with when making the connection, as they will hold the correct licences with the council to excavate the public footpath or highway.
If the valve that feeds the entire street isn't turned off then there will be a flood! Only the water company can do that switch off.
I have replaced my service pipe and I've worked in the water industry.

The external stop tap is located in the pavement around half a foot from our boundary , we have been told by the water company when we asked for a pressure check that the supply pipe is definitely lead and the communication pipe copper. We were under the assumption that if we use a WIAPS approved plumber they will not need pre approval from the water company ? And that we will be given a certificate to show the work was undertaken by them. Our only confusion came about when we were told by someone at the water company if we change our supply pipe we have to change the communication pipe regardless of the fact it’s copper.

This will only be the case if you a having a full new supply put in, it will be left with your new mdpe pipe sticking out of the ground , known as a pipe-out until it is passed. Then it will be connected. The street supply does not need to be turned off for this to happen. The main is tapped live. Replacing a lead section of pipework after the meter on your property can be done without any need to inform the water supplier.