Uhhhh??? Now I am scratching my head!. Why would I be worried about a bacteria growing in the water?
Taking the side of those that believe the water bath is a good thing.
One of the arguments against you is contaminants in the water. One specifically cited was salt, assuming most dive shops operate near a body of salt water. However there are other contaminates than simply salt that can be transferred as well even in fresh water. I believe through out this thread and the one reference article, the agreed solution to those contaminates is frequently changing your dunk tank's water. Presuming that would be done with already treated fresh water(tap), why would you need to add MORE chlorine (bleach) to that water? At least in North America most of the tap water already enough chlorine in it for a day or two. If your the shop is dumping the water, cleaning the dunk tank and refilling the tank with treated water regularly, why on earth would one need to add a possibly unmeasured amount of Chlorine in addition to what is there already? Is that water even tested before more chlorine is added?
What is the effect of an uncontrolled amount of chlorine on metal (the tank and value)? I think if a dunk shop wish to go longer between replacing the water they would be better off using vinegar (just an opinion, not an expert one). To me having to add chlorine 1) just says the shop is not replacing the water often enough and 2) because sh*t going to grow in it is another argument against the use of the water bath.
Out of this discussion a couple things come to mind.
1. I think someone in this thread stated after filling they take the tank to sit in a dunk tank (i.e. is not in the water during the fill). With a scalding hot tank in mind I cannot help but to picture a drinking glass (real glass) that has been taken directly out of a just completed dry cycle in the dishwasher and cold water put into it. The glass cracks and can explode. Again with a scalding hot tank does metal have the same response to the rapid temperature change or difference between inside an out. isn't rapid contraction just as bad for the tank as expansion? Please note I am not saying that the shop that takes the take to sit in a bath after filling and the one that delivered the scalding hot one are one in the same. It is more of a what would happen if, we will call them a new uninformed employee at the shop, filled tooooo fast then dropped the tank in the bath?
2. Does the argument for the ability to do faster fills hold water (sorry for the pun)? So even though we cannot see it with the naked eye, we know that during each and every fill the metal of the tank expands. The force of the air being compressed into it cause the molecules in air to be active causing the energy that contribute to the heat and additional force on the tank. When things settle down the metal will contract a little but never as much as it expanded. We are talking tiny tiny tiny changes. Agreed? While the heat of the tank after a fill might be an indicator of a problem, it is not the concern or real safety issue. It is that expansion that is more of the safety concern. More specifically, rapid expansion(or metal fatigue). Agreed? While the water bath may or may not keep the tank cooler; it may just keep the outside cooler and do nothing for the inside, Does it actually do anything for preventing that expansion (or slowing it)? Does it do anything to address that outward force on the tank during a fill?
I expect someone to come back and say yes it does using the argument that water does not compress. Okay but, all the tanks baths I have ever seen are not sealed and the tank is never completely submerged. The top of the tank bath is open and the neck (or more) of the tank and value are exposed. So does the fact that water does not compress stop or slow the tanks expansion at all? -OR- does the expanding tank simply displace more water - much like my fat body getting in to a tub full of water causing the water spill out over the edges?
If the water is not displaced and does help with slowing the expansion - wouldn't the part that is still out of water then get more force pushing out on it? While its not metal, think of a balloon that you squeeze at the bottom - the top expands, right. Wouldn't that be basically what the water is doing to the tank if it was controlling the expansion at all?
Science experiment time: For those that have bathes and believe they must be used - Take two tubs with an equal amount of water to start in both tubs; either measure the water you put in or do it by level without tanks in them; four tanks of the same type and size -fill two of the tanks in one of tubs(wet) and two tanks outside(dry); filling all four at the time and rate; after the fill put the two (dry) tanks filled out of water in the second tub. If the water level in both tubs is near the same with the tanks in them then the water did nothing or little for the expansion and the water is just being displaced.
Maybe the argument is that metal is more pliable with heat. So when the tank gets hotter it makes that rapid expansion quicker and easier; out of control. If that is true, I go back again to the parts that are out of water - they are neither getting cooled nor expansion controlled by the water. If you are controlling the energy both heat and force for only part of the storage vessel would that cause more energy to parts that are exposed? If heat causing the metal to be more pliable is the issue that would cause a failure, would it be an explosive catastrophic failure, or would it simply melt way a tear or hole through the metal?
Another Science experiment: Someone in the thread showed the temperature of a tank after a fill with an Non Contact Infrared Thermometer. Using one of those and during the fill bath (i.e not dunking the tank in a tub after the fill) - what is the temperature difference between the top of the tank (or neck) the furthest point not submerged in water and the bottom of the tank - the most submerged?
All things that I simply do not know but do have an opinion about.
What I do know is - Yes OP, a scalding hot tank with nothing else causing it than the fill, is a problem. A tank you pickup right after it has been filled will be warm - but not scalding hot. They filled it way too fast whether it was in a bath or not. Whether the tank is in a bath or not during the fill - I do not think it really matters as to the speed you should fill them. It should always be slow and steady. As you can tell it is a much debated subject as to whether the bath provides a benefit are more harmful. I do believe that the current overall thought, belief and trend is they do not have a benefit. There was only one shop my local area that had a bath, they quit using it with the agreement that after they had filled a few tanks the water was no longer cool enough to make a difference so they either have to swap the water out all the time or not use it. I do not know if that is true or not they have since closed their doors. All the shop local now only do open, none bath fills.
