Earlier this month I attached the toilet in my powder room to my high pressure rain water system. At the same time I installed a flow meter to measure how much rainwater I was using. I checked tonight, and after 10 days I used 206.1 gallons of water.
The other noticeable thing is the 1.8. My toilet clearly says "1.6 gpf" right on it. That's either a lie or the meter is wrong. I guess since the water is free I shouldn't worry too much about it.
I should also note that not all 206 gallons was due to the toilet. I did wash my cars the other day. I checked the meter then and had used about 30 gallons.
I'm happy with the result, but it doesn't tell the entire story! The flow meter only measures the high pressure water going through the pump. It doesn't measure the low pressure drip irrigation system. I'm saving water there too! I just don't know how much. I connected the flow meter to the drip irrigation line, but the flow was too slow to register.