Why do we have to drain the w heater at the tank?

[wdonovan]

Basic Atwood heater layout diagram show cold comes in the bottom, hot goes out the top of the tank. If cold is at the tank bottom, why doesn't the tank drain when you open the low point drains?

[The Hoff]

Mine did. It has something in the nautilus you have to turn and it will drain. Open air pressure valve and you will hear it drain. Did it on two different GD RVs.


2019 RAM 3500 Longhorn Megacab
2021 RAM 3500 Blackout Megacab
2019 OpenRange 3X427BHS
2020 Jayco NorthPoint 382FL
2021 Luxe Elite 42FL
2022 Grand Design Solitude 380FL-R

[xrated]

In order for a liquid to drain out of a sealed container (let's use the water heater for example), there has to be something to replace the volume of the liquid that is being drained....remember, it's a sealed container. So the most common replacement it air coming into a container, replacing the liquid that is coming out.

[sande005]

Basic Atwood heater layout diagram show cold comes in the bottom, hot goes out the top of the tank. If cold is at the tank bottom, why doesn't the tank drain when you open the low point drains?

Mine does, completely. I still pull the plug, just to check. Maybe one of these years I'll begin to have trust.

[wdonovan]

Oops! Sorry I forgot to mention. Before I opened the low points, I opened all faucets to allow the system to breathe. I also opened the pressure relief valve on the tank but it made no difference.