Tap water in Sweden is of high quality and is perfectly safe to drink. However, contaminations may occur.
If the tap water is suspected to contain harmful bacteria, viruses or parasites, the municipality may issue a recommendation to boil the water. In that case, water used for drinking or cooking should first be brought to a heavy, rolling boil.
In case of a shortage of potable water, the municipality may deploy water tanks, so-called emergency water. There may also be pre-assigned tap sites where you can fetch water. Contact your municipality to find out where these sites are located. Bring your own vessels to fill up.
During large-scale power outages that may occur after storms, for instance, running tap water may stop working. So whenever storm warnings are issued, it is advisable to store water in advance.