Water is becoming a contentious issue in strata where most of us only have one water meter for the building.
Even if it is legal, I don’t think attempting to split the bill by the number of occupants is equitable either. Someone who is water-conscious and has 3-minute showers with an efficient showerhead running at 9 litres/minute can still end up subsidising those having 10-minute showers under inefficient heads running at 30 litres/minute.
Your water consumption does appear to be excessive. If for example you’re under Sydney Water that is currently charging $2.13 per kilolitre, a rough calculation shows your usage to be around 320 litres/bedroom/day. This is on the high side according to the recent benchmark data for apartments. More information on that is at http://www.greenstrata.com.au/category/know-where-your-water-used.
There are several options you could consider. Unfortunately none of them are quick and easy, and they’re also dependant on how your building is plumbed, and how old it is. A very quick summary of them is:
(1) Eliminate a single cause
If your consumption increased dramatically at some stage, there could be a serious leak or a problem with the meter. You’re obviously on to that one with what your plumber is doing. Some buildings in the past noticed huge increases when their water meters were changed, because there was a faulty batch.
(2) Individual water meters
This is the ideal equitable situation, but has physical, logistical and cost issues. If you want to spend time investigating this I suggest you talk to your water utility first. If it is physically possible depending on how your building is plumbed, you also need to have assurance that your water utility will have easy access to and will actually read the meters. The cost of doing this will also depend very much on your current plumbing.
(3) Individual sub-meters
The next-to-ideal solution. Your water utility would still bill your owners corporation for total water consumption, but you’d allocate each apartment’s share by reading the sub-meters yourself. So there are upfront installation and ongoing administration costs.
(4) Building-wide water efficiency project
Sydney Water’s study identified that over 90% of building-wide consumption is within apartments (info on this also at the above link). The steps to decrease consumption are the same as in houses – water-efficient fixtures, fittings and equipment. It’s just more difficult to achieve because you can’t force people to make changes inside their apartments. What you can do however is make easier for them.
A common approach these days is for the owners corporation to pay for and organise services such as Sydney Water’s WaterFix (https://www.sydneywater.com.au/Water4Life/InYourHome/WaterFix/index.cfm) . The payback on that is generally less than 12 months so it’s well worth the effort.
I know of a 70’s building of 14 units that reduced its consumption by 47% by facilitating the WaterFix and Toilet Replacement services (replacing single flush with dual-flush toilets) building-wide.
(5) Annual inspection of all units
Unfortunately some occupants don’t do anything about leaks until they’re drastic and have also caused other damage. In a lot of cases we know of terrible leaks that no-one knows about until occupants change. An annual inspection for leaks, combined with inspecting those parts of common property that can only be seen from within an apartment, are beneficial both for keeping on top of consumption and also budgeting for common property maintenance.
(6) Pass a by-law to avoid overcrowding
Seven occupants in a 2-bedroom apartment are too many. Overcrowding is a growing issue that not only impacts water consumption by also fire safety. Many buildings are facing this problem and are implementing by-laws that restrict occupancy to 2 adults per bedroom.
Cheers
Chris