I use the standard 20 qt brewing pot for mashing exclusively. I actually had two of them from my earlier bout with brewing in the mid-90's. I heat the sparge water in the second one.
I keep the mash in the oven to maintain temps, then "Pyrex" it over to a stainless pasta strainer to collect the first runnings, which I run back thru the grains into the first (mash) pot after I first clean it out. (The strainer size and my back strength limit my grist to eight pounds and ten quarts of water.)
So the mash pot becomes the boil pot, and I continue to sparge and add wort to the boil pot until it's full and topped off. It is labor intensive and creates a few dirty pots, but I'm utilizing assets paid for long ago. The primary physical demand is lifting the full mash pot in and out of the oven, ~30 pounds.
I personally prefer to stick with all-grain, so my batch size is about 3.7 gallons, but you could easily add DME to reach normal gravities and 5 gallons for most beers. I brewed a pumpkin ale Wednesday and my friend brought his bigger boil pot, so I sparged more and we only needed 0.5 pounds of DME to reach 1.052 for ~4.5 gallons.
Cowboy - If you are interested or have questions, feel free to PM me. Below is an ESB I did today if you want to see how the numbers play out for a small-batch, all-grain recipe using this type method.
Particularly with BeerSmith, this method is very accurate with strike water forecasts since the pot is pre-heated. I was within 0.5 degree F this morning. Pour, stir, put in oven.
Style: Extra Special/Strong Bitter (English Pale Ale)
Recipe: 08C English Pale Ale v2 TYPE: All Grain
---RECIPE SPECIFICATIONS-----------------------------------------------
Est SRM: 12.8 SRM SRM RANGE: 6.0-18.0 SRM
Est IBU: 52.3 IBU IBU RANGE: 30.0-50.0 IBU
Est OG: 1.061 SG OG RANGE: 1.048-1.060 SG
Est FG: 1.016 SG FG RANGE: 1.010-1.016 SG
Est BU:GU: 0.858 Calories: 275 cal/pint Est ABV: 5.89 %
EE%: 78.00 % Batch: 3.90 gal Boil: 4.50 gal BT: 65 Mins
Total Grain Weight: 8.19 lb Total Hops: 2.00 oz.
---MASH PROCESS-----------------------------
Single Infusion, Medium Body, Batch Sparge
Step Time Name Description Step Temp
60 min Mash In Add 10.24 qt of water at 164.2 F 152.5 F
10 min Mash Out Add 0.00 qt of water at 168.0 F 168.0 F
---SPARGE PROCESS---------------------------
Add first wort hops during sparge
Amount Item Type % or IBU
0.50 oz Challenger [5.70 %] (70 min) (First Wort Hops 17.8 IBU
0.50 oz First Gold 7 [6.70 %] (70 min) (First WorHops 20.9 IBU
Sparge with 2.92 gal of 168.0 F water.
---BOIL PROCESS-----------------------------
Est Pre_Boil Gravity: 1.053 Est OG: 1.061 SG
Boil Ingredients
Boil Amount Item Type
30 min 0.25 oz Challenger [5.70 %] (30 min) Hops
30 min 0.25 oz First Gold 7 [6.70 %] (30 min) Hops
15 min 0.25 oz Challenger [5.70 %] (15 min) Hops
15 min 0.25 oz First Gold 7 [6.70 %] (15 min) Hops
13 min 1.00 items Whirlfloc Tablet (Boil 13.0 min) Misc
10 min 2.20 gm Wyeast Nutrient (Boil 10.0 min) Misc
9 min 1.00 items Wort Chiller (Boil 9.0 min) Misc
---NOTES----------------------------------------------------