Measuring water volumes

[Foghorn]

I am having issues with the volume of water going into my boil pot! I can measure the volume going into my mash tun(cooler). I batch spare so I am having issues measuring the amount of water coming out, and ultimately my boil volume. I thought of just using a measuring cup but as the hot liquid comes out but at 150 degrees I don't want to get burnt. I measured my deadspace at about 1 quart and I get another 2 quarts out of the mash tun while the boil happens. Not sure if that is considered deadspace or not? Is there a way to measure (inexpensively) the wort coming out, or do I just need the dial in my system and math procedures.
My last batch I added 7.25 gallons to 13 pounds of grains and got back approximately 6.5 in my boil. I will need to very my "deadspace" but any ideas?

 

[kh54s10]

Forget all the calculations.... Make a dipstick. Ideally heat the water to mash temperature (4% expansion with heat), measure a gallon of water and put it in the BK. Mark this level on your dipstick. Repeat until you have enough marks for your batch size. Mine is just over 7 gallons to end up with just over 5 into the fermenter.

Or for added bling, add a sight gauge to your BK.

After a few boils you will know your boil off rate, then you just collect enough wort for the preboil amount and start the boil.

 

[acidrain]

You can squeeze the last bit of wort by pressing the grain bed with a lid.
Then calculate how much more wort you need for your pre-boil and add that amount of water for your sparge. You should collect the exact amount needed (you may have to squeeze again), but yeah... you have to be able to measure those amounts somehow.
The amount left in the tun that you cannot get out is the deadspace.