Gravity feed recirculation system
ericmueller
| Posted in Construction Techniques on
I have an existing gravity/convection recirculation system in my home that works very well. I’ve recently finished the basement and added a bathroom and a bar with a sink and dishwasher. Can I create a second recirculation system that returns to the hot water tank at the same place as the existing system, or do I need to extend the existing system. If possible, I’d like to add the second loop system based solely on the fact that it will require significantly less materials. Thanks.
Eric
Replies
Fist, I'm not a plumber.
Second, if it is a true gravity recirc system, it needs an elevation change to work. In our home in Raleigh my plumber installed it and we loved it, but the master bath was on the second floor and the water heater in the basement.
Unless your hot water heater is at the bottom of a well I don't think you could use a separate loop for this.
Let's not confuse the issue with facts!
I use the term gravity feed since that's what they're commonly referred to as, but in reality it's convection, not gravity that makes the system work.
True that, but - 'not to confuse the issue with facts' -would a 'convection' system work without an elevation change, to allow the cold water to 'fall down' to get the recirc going? Does this not make it, at least partially, a 'gravity' system?Let's not confuse the issue with facts!
Gravity is essentially the attraction of particles to one another, which has nothing to do with the principle that makes this system work. This system works because when a vessel of water is heated, the warm water rises while colder water descends. As the water heats and expands, the column of hot water in the supply line will push the slightly cooled water ahead of it. You need to have the heat source below the level of the horizontal runs, otherwise, the warm water would just collect at the top of the tank.
I can't think of a theoretical reason why 2 separate loops connected to one water heater won't work, but I'm hoping that someone has some practical experience and can confirm that it will work.
Au contraire - gravity is exactly why this system works. Cold water sinks because it is more dense than hot water and thus is acted upon with more force by gravity than the hot water, which is pushed about as the cold water is pulled downward. On the space station with no gravity, there would be no circulation of the water in such a system. To work, there needs to be a column of cold water of sufficient mass pushing down to push the column of warm water up to where it is wanted. The weight of the cold water needs to overcome the friction of the pipes as well as the mass of the hot water. I have no idea how tall the section of cold water must be push the water to where it is wanted, however.If the height differential of the top and bottom of the cold water pipe is not sufficient to move the water through the pipe, an auxiliary pump can be used. Someone a couple of days ago posted the link to just such a pump that is activated as desired to move warm water to the faucet:
http://www.gothotwater.com/
I've been told 8' is a good starting height. Never tried less than that.