More accurate way of determining pre-boil Eff?

OK, I am going to ask a dumb question. Typically when I mash, using 1.25 qts/lb. I drain, and batch sparge twice to get my boil volume. I pour all of the wort into the Keggle, mix, and take a reading for the pre-boil volume OG.

Would it be MORE accurate if I took readings coming out of the MLT at each phase, added them together and divided by three?

Does anyone have any insight on this? Have I been doing it wrong? Or would the result be the same?
Thanks

Prost

You are doing it the correct way, taking 3 different readings of not necesarily the same volume and adding them up is less accurate. The formula takes in to account the potential extraction per pound per gallon, so if you were to look at the efficency of just your first batch sparge say 12lbs per 3gallons you would get horrible numbers. Similarly if you look at the last runnings there is not much to be extracted there. I can't type effectively enough to go into depth explaining this, but you are doing it correctly, keep doing it that way.

I typically take readings for each runnings, but they are only useful if you also know the exact volumes of each. I use the gravity of the runnings to predict my pre-boil efficiency before I am done sparging, particularly for higher gravity brews where extract efficiency tends to suffer. If I see I am undershooting a bit, I adjust my sparge water volume to collect some additional runnings and boil a bit longer to reach my target gravity.

Of course, if you only get the gravity of all the runnings, you can still adjust your target gravity with some DME or water, as necessary. That's the easier method, IMO. Also, if you were comparing the accuracy of measuring gravity using separate runnings vs. the combined runnings, the latter would be more accurate since you only have one (large) volume of wort to measure and only one gravity measurement (less room for human error than three separate readings).

Cool guys thanks for the replies. Since I am batch sparging, I will just keep mixing it all together and then reading it.
Thanks again