To All, I have a 2015 409 and connected the bypass for winterization and dummy me I did not take a picture. In putting it back together one of the original 15mm tube pressure fittings leaked and did every combination to confirm. Put in new metal mesh hose(s) and upgrade fittings and tubbing...perfect. The question I have is the tank has a red plastic ID ring on the top water input fitting (has a temp adjustment knob) and blue color plastic ring on the bottom water input fitting. I connected hot water tank to the main water line to corresponding colors red to red and blue to blue but seems strange the cold water would fill the tank from the bottom? Did I do this right or do I need to switch the cold water to feed the hot water take from the top fitting?
There are two advantages in having the cold water enter at the bottom and the hot exit at the top.
One is that if there was an interruption to the cold water supply but the hot water could still drain, there would be a possibility of overheating the element and burning it out in an electric hot water system, or just boiling the water, causing salt deposits which degrade the heating surface performance. Of course, in our case, it is hard to see how the hot water flow could continue if the cold water stopped. Perhaps a leak low down on the hot water side.
The other reason is just function. If the cold water entered at the top, it would descend through the hot water due to its higher density, thus mixing the hot water with the cold and lowering the temperature throughout. You would have to continually adjust the hot water for your shower, and the water for washing up would probably be too cold to be effective if you used more than a tiny proportion. Easy to do in such a small tank. Putting the cold water in the bottom means that the density difference causes the cold water to stay at the bottom, reducing that mixing, so the hot water exiting at the top stays at a higher temperature for longer. The total amount of heat involved is the same either way, but by keeping the hot and cold separated a little, you effectively get hotter water for longer before the whole lot is overwhelmed by the incoming cold. Your home hot water service is probably similar.
The humble Boy Scout camping water heater made from a kerosene tin/drum with a funnel at the top for pouring in the cold water has an internal pipe from that funnel to the bottom of the tin, and the hot water overflows from an outlet at the top as more cold is poured in through the funnel. As the fire heats the water at the bottom of the can, it only rises when it is warmer and therefor less dense than the water above. There is always water in the drum so the metal never gets red hot. My scout group always had one of these made from a five gallon drum as part of the camp kitchen facilities.
The actual connection arrangement is affected by the parts we can’t see on the inside, so always best to double check what was intended. But those coloured rings are the clue in this case.