Ask the municipality or water association who owns the pipes or who is responsible for their maintenance – the municipality or the farm. Also check the register of construction obligations; the building authority is your contact.
If they belong to the municipality, you will certainly be able to relocate them for construction purposes (who pays for this is another matter). If they belong to the farm, then the farm needs an easement. Whether this is the case should be shown to you by the seller with a current land register excerpt (the second part of it is your friend). If this is not available, then they are out of luck; you can cut the pipes after giving notice and waiting. There is something like an emergency pipe right, but this requires choosing the least possible burden on the party obliged to tolerate it, meaning: at the farm’s expense, you can lay the pipe in such a way that it no longer interferes with the construction project.
If there is an easement in the land register, then it is legal. In that case, you must come to an agreement with the farm; or I would consider the property value to be significantly reduced.