Fly sparging Temperature regulation question

Books I've read state that the sparge temp should be no more than 170 degrees. I know I'm going to lose some degrees after the water goes through the plastic tube and the sparge arm. I'm looking for some advice on how to regulate the temp so it's in the proper range once it reaches the grainbed. I'm using a 5 gallon round iglo cooler for my hot liquor tank and a 10 iglo cooler for my MLT. I've been adding 5 gallons of water in the Hot liquor tank temps around 175-178 degrees "hoping" that it reaches the right temp by the time it gets to the grainbed. Am I making more out of this than need be?

Only one way to find out, take the temp with a thermometer coming out of your sparge arm and adjust accordingly on your next batch. Sounds like you are already on the right track and should be fairly close.

I get pretty close by doing a mash out first to raise the grain bed temp to 168 - 170, and adding 185 degree water to the HLT. I don't bother to pre-heat the MLT, so it cools down somewhat before I use it, and I have long tubing, so it loses more temperature on it's way to the sparge arm. It also varies with the sparge rate. I spent a few brews testing the temperature of the grain bed during the sparge before I got something that suited my equipment, but increased my efficiency by 10%.

-a.

What I haven't been doing is mashing out so I'll try that next time before I start sparging. Thanks to all for the advice

I add enough nearly boiling sparge water to the mash to bring it up to 168º. The rest goes into my HLT at about 180º.

Yeah, I wouldn't worry too much about the temp of the sparge water. The main this is not to let the grain bed temp get above the 170-175*F threshold. My understanding about tannin extraction is that it is a combination of the temp and the pH climbing through the sparge process. Otherwise, batch spargers would have have tons of tannin problems and they don't.

I usually sparge with water in the 175-180*F range after mashing out and the grain bed temp will actually fall or hold at 168*F for the duration of the sparge.