How to deal with AG in a 7gallon kettle

[Surye]

I was thinking of moving to all grain, planning on buying a 10gallon cooler to convert to an MLT this weekend, before summer price gouging.

My problem is that I don't have a very large kettle, and I have to boil stove top (for now anyways). After mash and sparging, I expect I'm going to need more boil capability than ~6gallons I can fit in my kettle.

My question is if I can use my other 5 gallon kettle to pull the last of the sparge water, and boil that at the same time, and after evaporation from both, combine them? What would be the issues involved here? Would I have to do the combination before the first hopping (meaning 90 min boils), or could I just hop the mash and add the sparge water at the end? Would there be a better solution than this?

My first grain bill is 15 lbs, so I think this will be relevant.

 

[BlindLemonLars]

For starters, look into ferm-cap. Just a few drops in your kettle will allow you maximize your kettle volume without fear of boilover. It's great stuff, and makes my brewdays a lot more relaxing since I don't have to babysit the kettle.

I'd just boil the final runnings in a second pot, and add them to the main boil once the level has boiled down enough to allow it. Since your main boil will be a little more concentrated, you may have slightly lower hop utilization. Honestly though, I wouldn't worry about it, and I certainly wouldn't let it stop me from switching to AG!

Meanwhile, start looking for deals on a 10 or 15 gallon kettle...once you find one, you can use your 7 gallon as a hot liquor tank.