What's a good soaking temp? I can be more precise now that I have a temp gun.

Warm. Like what you would use for a baby.

The temp of the water should be comfortable when you place the back of your hand into the water. If it feels too hot, it probably is too hot to put your baby in.

standard hot only water is 120 which is scolding. 88-92 is a good temp for a soak.

Does a temp gun really work well on the surface of water? I'd think you'd get low readings due to evaporation. I used the outdoor probe from a wired thermometer. They are made to be water proof since they sit outside. I like my water right around 90.

Might be 1 silly question. But why use the warm water? I do that at first when I first adopted all my torts during holiday time. But then I need to work, then I learn that my maid has been soaking using normal tap water in the morning. But all the torts have been pooping like normal using normal tap water. So now I don't change the routine.

Because most of the time the water coming out of the pipes is pretty cold. Not a good idea to have a cold wet tortoise.

The tortoise will become the same temperature of the water very quickly, but will take a long time to warm back up. Also, who likes to sit in cold water? I think that the water/air ratio for warming/cooling is about 10:1

I agree that sometimes water coming out of the pipe will be a bit colder, so that might be a problem for country with winter season and we sure don't want our torts to get sick due to it.

Also agree as they are cold blooded animals, but we have the basking spot for fast warming up purpose right?

I use a real scientific method. I run the water in the faucet until it reaches a nice warm temperature (felt on the same wrist I used to use over 40 years ago to test the temp of my baby's bottle).

I leave the babies in this same water for at least 15 minutes. I don't worry about the changing temp or the cooling of the water. My house is usually in the 70's F and the water isn't going to get any cooler than room temperature and 70'sF is perfectly fine for babies.