Dear Steven Patrick Marshall

This method little bit practical but let have a try, Take the amount of water in the jug in litres (e.g. 0.8 litres) and multiply this by 10. This will give you your flow rate in litres per minute (e.g. 0.8 litres x 10 = 8 litres per minute).

Kind Regards

Qamar Ul Islam

Flow rate is volume divided by time. So just put a floater and determine the time the floater goes round. Secondly determine the volume of water that you are stiring. This will give you a flow rate. Though this flow rate is higher than the middle one.

I think by using some simplifying assumptions, the volume flow through an open bathtub may be estimated with the Bernoulli equation.