Possible to modify old kettle into mash tun?

I've been doing specialty grain/extract for a few brews now and have finally ordered a new kettle (32qt) with tap and thermometer, something I can really get a full-batch boil going on in. My old kettle is 20qt (5gal) and I was curious, if I put in a false bottom, have a spout put on it to run off the wort into my kettle, is it feasible (or really even worth the effort) to create a mash tun out of the old SS kettle? I've seen some really nice, higher end home systems that have a trio of SS pots staggered to create a nice set up, but wasn't sure if this would be possible to do on my smaller scale.

I suppose the real question comes down to:
Is 5gal large enough to accommodate the mash?
Is this SS kettle going to lose too much heat during the rests?
Anyone have experience with a system like this?
Any suggestions of what the smaller kettle could still be used for?

you def can convert it to a mash tun, you may be a little restricted on the amount of grain you can mash in it but it'll def work none the less

For 5 gallon batches a 5 gallon vessel is large enough for the mash but you'll be limited in what you can do. Search for the chart of how big your mash tun needs to be for different size batches/gravity beers.

You'll likely lose a lot of heat but you can insulate with Reflectix to help, or use a pump and flame to recirculate the mash to maintain temps. To do that you might start to consider bigger equipment though...

I think the majority of people doing 5-gallon batches use the cooler type mash tun. They are easy to make and pretty inexpensive if you buy the parts locally and not fully assembled on a supplier stores website. Search Cooler MLT and you'll find the thread in no time.

You could use the smaller pot as is for heating sparge water, use it for soaking bottles on bottling day, use it for smaller test batches or extract batches you might do down the road. Lots of uses for a nice SS kettle in the world.

I agree with Slow. You will be quite a bit limited in the beer you can make, because you can only accomodate so much grain/water in the mash. Because remember, your false bottom is going to take up some space on the bottom of the kettle, so you dont actually have the same amount of space you have now.
However, you would be able to convert it by doing exactly what you said; get a false bottom and pop a ball valve on the side. Heat loss could be dealt with by actually keeping the pot on an open flame (such as on your stovetop), just reguating the size of the flame to keep it at mashing temps.
I use my old 5gal kettle as a Hot Liquor Tank for sparge water.

A SS pot will not lose heat very quickly. If you wrap it in a blanket, you can probably manage to maintain your mash temps even without adding extra heat. Besides the volume limitations, it will make an excellent mash tun. Then later, you can always buy a 40qt cooler for higher gravity beers, and use this pot for experimental batches. You won't be out any more money than the valve and/or thermometer and false bottom you add to your pot.

I'd say go for it. The risks are minimal, and you can always upgrade later if needs be.

It's possible, but I say just go for broke with a big cooler and fittings. You will probably want to end up making that investment anyway. Just my two cents. But don't let me stop you! This hobby's all about experimenting with your system.