Little Baptism Help?!?!?!

I have a practical baptism question. Since Tapestry is what would be referred to as a nomadic church (i.e. a church without a building – though I also like the idea of us as being a raiding party) our baptisms are usually done at one of two places: Warm weather = Iverson Park, cold weather = the Metallo’s hot tub. It works really well and I love baptisms, both for the proclamation of faith that happens during the baptism and the fun everyone has together during them (baptisms for us equal potluck dinner). It is a really good setup that I don’t want to change in any long term manner,

With that said, I would like to try at least one baptism at the school where we normally meet (Washington Elementary School). Anyone have any ideas for a tank big enough to dunk someone in, that could be setup, filled, and (this is key) brought to room temperature in 2 hours and then completely torn down in 45 minutes? We have 4 hours total at Washington which makes things a little difficult and it costs us per hour to reserve more time.

Sometimes it would be so much easier to just sprinkle. 😉