Get the owner of number 3 to pay for and sign a legal agreement (written by a lawyer and notarised) that they will
- Have the valve fixed immediately
- pay for it themselves
- indemnify the owners corp in perpetuity against any costs resulting from the repair work.
- allow the owners corp access to the property for estimates and repair work if the valve is not fixed withing 14 days.
Something like that …
Otherwise you can commence action at NCAT under Section 122 (Power of owners corporation to enter property in order to carry out work) If it’s a genuine emergency you can probably get orders more or less immediately allowing you to demand access. If they refuse, there’s a maximum fine of $550.