TET & deadlegs

[Tom098]

whats the view on TET's creating dead legs - i know they are typically on the cold side but IMO with a long branch its still a deadleg?

 

[Reach4]

Not dead normally. When you take a shower/bath, and turn off the water, water flows into the thermal expansion tank. Then, water flows out.

 

[Sponsor]

 

[Tom098]

Thanks for the reply but the post before mine today showed a sketch of how that user name would install his TET on a branch.
on a branch like the one in the sketch the water in the pipe would not be drawn down when hot was supplied - the incoming mains pressure might overcome & isolate the branch water head pressure? Hence, water in the branch might, in time, become stagnant?

i ask the question out of curiosity.

 

[LLigetfa]

An expansion tank would normally be empty and only take on water when expansion happens. When water is used, the extra pressure is bled off, which drains the tank.

Your post is the first in this thread. There is no post with a sketch before yours.

 

[Tom098]

my mistake calling a thread a post.

Reach4 posted a sketch yesterday in the thread before mine, his post showed a sketch of a possible TET position in an installation.

Depending on its position & location a TET would not "normally be empty".
Pressure, of course, varies. But there is always water in the TET tank.
However, my question concerns TET's on branch lines where it might be possible for the water to remain stagnant in both the tank and the pipe?

 

[Reach4]

my mistake calling a thread a post.

Reach4 posted a sketch yesterday in the thread before mine, his post showed a sketch of a possible TET position in an installation.

Depending on its position & location a TET would not "normally be empty".
Pressure, of course, varies. But there is always water in the TET tank.
However, my question concerns TET's on branch lines where it might be possible for the water to remain stagnant in both the tank and the pipe?

https://terrylove.com/forums/index....all-thermal-expansion-tank.86412/#post-620001 is the post you are referring to. The location of other posts can vary with how the person is viewing things, and if one of the posts gets a follow-up. You could have linked to the post as I just did, or even put the picture in your post, like this:

Your concern is worth discussing. I maintain that there will be normal sufficient flow. I think reducing the path to 1/2 or 3/8 or 1/4 inch pipe would increase the washing-out, but there will be daily flow in occupied houses that use hot water, I think. I am not a plumber. I believe if this were a problem, there would have been more discussion, and even code changes. Maybe you are starting the discussion that will lead to code changes or clarifications. Maybe, in some future code, there will be some limit to the volume of pipe that can be used to connect to a thermal expansion tank.

 

[Phog]

I'm not sure if this is helpful at all. And I'm not sure what plumbing codes have to say about this; but I can't think of a functional reason why the expansion tank has to be near to the water heater. From a functional standpoint it can be located anywhere in the home's plumbing system & still do its job (as long as it is not isolated from the hot water tank, for example by a check valve). You could put the TET on the other side of the wall, or 30 feet away, and it will still take up the expansion.

 

[Reach4]

I'm not sure if this is helpful at all. And I'm not sure what plumbing codes have to say about this; but I can't think of a functional reason why the expansion tank has to be near to the water heater. From a functional standpoint it can be located anywhere in the home's plumbing system & still do its job (as long as it is not isolated from the hot water tank, for example by a check valve). You could put the TET on the other side of the wall, or 30 feet away, and it will still take up the expansion.

I agree, with an exception that you would want to avoid putting it before the water softener, if you have one. The reason is that the flow could be measured both ways, as it goes through the softener. The turbines just report the turns and do not distinguish direction. Yes, the volume is probably not all that big, so it would not be a big deal in practice.

The opposite can occur for people with city water which has pulsating water pressure, and there is no check valve. For those, the pulsations can run water into and out of the tank at the WH. The turbine can be ticking off flow. This is pretty rare.

 

[LLigetfa]

Depending on its position & location a TET would not "normally be empty".
Pressure, of course, varies. But there is always water in the TET tank.

Not true. A properly charged tank would have higher air pressure than the baseline water pressure. Water only enters the tank after expansion raises the pressure.