If your supply runs dry you need to be prepared for outages, extreme dry weather, someone disconnects your supply, contamination.
There are things you can do to prepare:
Ask friends, neighbours, or family for help. If they are on public mains water, you could perhaps fill containers
Treated water tank in a bowser but ask the supplier if they comply with BS 8551:2015 (Provision & Management of Temporary Water supplies and distribution networks code of practice)
If you are a commercial business or a private landlord then you will need to have a contingency plan in place on how to deal with a lack of water
Water suppliers of treated water and water engineers can be found on the internet. Alternatively if you contact the Council they will be able to provide you with a list but cannot endorse any companies
