Let me share with you a very costly assumption.
Last month I had one of my small investment properties become vacant for 36 days in between tenants. This is a 2000 sq. ft. industrial unit with 2 washrooms. So the hydro bill comes directly to me for the 36 day time frame until the new tenant takes over. I was shocked to find a water usage of 63 cubic metres (220 gallons per metre) and at a cost of $215.00. I immediately called Oakville Hydro to tell them they made a mistake reading the meter and I actually accussed them of not reading the meter but just assuming the amount because of the previous tenant's use of water in the unit. They said they physically went to the unit and read the meter when the old tenant vacated, and again when the new tenant moved in. I again protested the amount of the bill because but no one had been there during the 36 days to use the water. The person I was speaking to told me the biggest use of water often comes from leaking toilets and I should go and inspect them. So I did, and I found that both toilets were leaking very slowly from the tank into the toilet bowl. The cause was the flapper valve not creating a tight seal when it closes each time after a flush. This valve comes down with gravity as the tanks empties and does not always create a tight seal. It appears that after 3 to 5 years the rubber wears out and small leakage starts.
Flapper valves are only $6 items at Home Depot and can be easily installed using the great instructions that come with them. So do yourself (and your family and friends, and the environment) a favour and inspect your toilets. Is is estimated that 80 percent of all toilets will leak a bit - even new ones - simply because of ill fitting flapper valves. If I had not experienced this myself, the new tenant, who does not use water other than for personal needs, would have had an approximate $3000 water bill this year. After I brought this to his attention he immediately shut off water to both toilets and went to purchase two new $6 flapper valves. He then thanked me for being a good landlord who cares.