Most plumbing companies will sell you an annual maintenance plan. Some of it is worth doing. Some is not. Here is the honest take on what is actually useful.
Worth doing every year
Clear your roof gutters and downpipes. Done in October before summer storms. Cost $150 to $300 if you hire someone, or a Saturday morning if you do it yourself. Prevents most storm-related water damage.
Check stormwater pits and grated drains in the yard. Lift the lid, clean out any leaves and debris, run a hose to confirm flow. 10 minutes per pit. Done before storm season.
Lift and clean bathroom drain grates. Pull out hair. 5 minutes per drain. Prevents the gradual slow-draining problem.
Worth doing every 2 to 3 years
Inspect under all sinks for flexi hose condition, P-trap leaks, and any signs of water damage. Replace flexi hoses if they are more than 10 years old or showing any corrosion.
Check your hot water system. Pressure relief valve still working, no rust at the base, no leaking. Replace anode rod every 5 to 7 years for storage tanks.
Worth doing every 5 years
Get a plumber to do a full house plumbing check. Costs $200 to $400. They look at everything: taps, hot water system, gutters, stormwater, accessible drain lines. Catch problems before they become expensive.
If your house is older than 30 years and you have not done it before, get a CCTV sewer inspection. Cost $250 to $400. Tells you the condition of your underground sewer pipes. Lets you plan any future relining or repair before it becomes an emergency.
Worth doing for older homes
If you have terracotta sewer pipes (most pre-1975 Melbourne homes), consider a yearly maintenance jet to keep tree roots back. Cost about $400 to $700 per session. Cheaper than full relining if your pipes are otherwise in reasonable shape.
Not worth paying for
Most monthly plumbing maintenance plans. The actual work that gets done is usually less than the annual fee. You can do most of it yourself or pay for individual checks as needed.
Chemical drain treatment products marketed for prevention. Mostly snake oil. Hot water and a clean grate do more good.
Insurance plans that bundle plumbing emergencies. Usually expensive and excluded for the things you actually need them for. Better to keep an emergency fund.
The bottom line
Annual gutter clearing and a 5-year plumbing check. That covers most of what is worth doing. Plus prompt attention to any problem you notice, rather than waiting for it to get worse.