Work on fixed water and heating installations needs an autoriseret VVS-installatør (authorised plumbing contractor), or a firm that brings one. Ask which it is, and ask for that on the invoice (faktura). Authorisations are looked up at Sikkerhedsstyrelsen, sik.dk.
Horsens has a tight centre and houses further out. The harbour and older apartments downtown are a different access problem from newer terraces. The same 4 businesses as the Danish page: ADELHOLM VVS ApS, HON VVS A/S, MØLLGAARD BYENS VVS A/S, Åes Smedie & VVS v/Søren Roslyng.