To find out the actual output and the variations on a Stenner pump, we did a very informal test with a new 220 volt 10 gallon-per-day Stenner metering pump.
We used a stop watch, a pail of water, and a standard kitchen measuring cup.
The pump has a 1 to 10 setting wheel.
Here's what we found:
On the highest setting, 10, the pump produced about 11.8 gallons per day.
On the middle setting, 5, the pump produced about 5.9 gallons per day.
On the lowest setting, 1, the pump produced about 1.8 gallons per day
There is an ultra-low setting below 1. The production is noticeably lower than the 1 setting, but we lost patience and quit before we could get enough water in our measuring cup to yield a calculation.
The Moral: There is a great range variation, but the manufacturer's output rating seems to describe more accurately the high range than the mid range of the pump.
(whole house & well units)