K
kirkgas
but i think the initial point of the post was(had to read it again) is that the engineer said it was ok to have a 4mb drop on the old pipework even with the appliances isolated..thats definetely a no no then isnt it
im not reading the whole post again, but i will answer your Q here, you are right it is a def no-no to leave ANY leak on a pipe only, (thats why a lot of people test existing carcass and existing appliances with the appliances connected, so that if there is a small leak it can be left operating)