Water loss and Calculation

I'm sure this has been asked before and is probably a dumb question but how should I calculate my boil volume? I use 2 10g rubbermaid coolers and a keggle. I lose 1 gal between both coolers and 2 gal remains in the keggle unless I tilt it. Should I over estimate by 3gal?

thx

Wow -- 3 gals is a LOT of loss. And that's not just water loss, that's mostly wort loss which is very different.

I use the same setup: 2 10 gal round coolers and a keggle. I lose less than a quart in each vessel. Are you sure you can't improve on your system? Do you have a pickup tube on the keggle? Seriously, if I were losing 2 gals from my keggle every batch, I would just rack out of it and skip the tap.

Anyways, assuming you can improve on your losses, some level is inevitable. Losses to deadspace in the mash tun, boil kettle, and chiller (if applicable) all take away from your volume in the fermenter. So, work backwards. If you want 5 gals in the fermenter, first add your wort lost to the boil kettle, then from that figure out your evaporation loss to get your pre-boil volume, then add to that your mash tun loss. That should be the target volume.

Thanks. I knew I missed something. Jeez I feel dumb. Should I just make a pick-up tube or add a false bottom with one? I've seen alot of designs, but is teflon tape ok to be in there?