Originally Posted By: psmothers This post was automatically imported from our archived forum.
There should be an dielectric union used to separate the dissimilar metals. It prevents the corrosion with a insulating sleeve and washer that “isolates” as you phrased it, the metals from each other. I have seen water heaters that have had both lines hot just due to not having water drawn from them for long periods of time and the heat in the tank transferring up the line. Another possibility could be if there were two water heaters in the home incorrectly installed together in “series.”
Wow its late! 
Originally Posted By: James D Mosier This post was automatically imported from our archived forum.
Peter,
How would you call out a set of water heaters plumbed in series? My old neighbors moved into a former "all electric" home. I attended the inspection last year. The inspector said nothing about the two water heaters in series until I brought up the fact that I thought it odd to preheat the water with electric then reheat with natural gas. He said it wasn't a preheat/reheat thing, that the size of the original electric tank probably wasn't enough for 5 baths and two kitchens.
Originally Posted By: Guest This post was automatically imported from our archived forum.
Uh guys,
The piece of galvanized there could in fact be a dielectric union. Normally they have a line in the center but I've seen them witout one.
The galvanized is 3/4 pipe thread and screws into the tank. Someone has mashed on a compression style fitting and forced it over the 3/4 tapered pipe thread. the rust on the copper is probably just that..rust. I imagine the fitting leaked a while before the rust from the galvanized sealed it up. The stain is probably just that, a stain and has nothing to do with the copper/brass connection. Copper and brass are very close to each other on a galvanic scale and need no isolation from each other.
If you look close at the stained area you can see the copper tapers down at the nut. Someone squeezed the bejeezus out of the tubing trying to mash the ferrule into the galvanized and get it to stop leaking.
Originally Posted By: psmothers This post was automatically imported from our archived forum.
Quote:
If you look close at the stained area you can see the copper tapers down at the nut. Someone squeezed the bejeezus out of the tubing trying to mash the ferrule into the galvanized and get it to stop leaking.
Good eye on that one, did not see it last night. You are 100% correct about copper and brass being very close to each other on a galvanic scale and not needing isolation from each other, not questioning that point.
James-
In larger homes or homes with special hot water needs there are two ways of correctly accomplishing this using standard hot water heaters.
1) You can install two separate water heaters in different parts of the house that serve different plumbing fixtures in effect creating hot water zones.
2) You can install water heaters side by side that are in parallel.
http://www.ccdeh.com/commttee/food/documents/Guidelines/water_heaters_in_parallel-drawing.pdf
The pipe lengths running through both should be the same length. When this is done both water heaters share the load.
The incorrect way would be to install two side by side water heaters in series. This means that the 2nd water heater would be feed by the 1st and the 2nd would rarely turn on leaving the first to do most of the work.
How would you call it out?
Just state "The two side by side water heaters are incorrectly installed in series. Consulate a licensed plumber for review and repair as needed."
Originally Posted By: jsavino This post was automatically imported from our archived forum.
The piece of galv. pipe was not factory installed, but that’s OK. The pipe was installed so that no heat got to the plastic drip tube inside and melted it during the sweating of the pipe.
The installer should have used a 3/4x female copper adapter in place of the compression nut, which I’m suprised it held.
Did you check the temp. setting of the tank? Did you run the hot water? Did it remain hot or did it get cold after a minute or two?
Could just be as easy as a heat transfer up the drip tube, or the drip tube may be damaged.
-- John Savino
HomeWorks Inspection Services, LLC
St. James, NY
631.379.4241
Originally Posted By: Guest This post was automatically imported from our archived forum.
These have a plastic liner and qualify as dielectric as well. Some of them even have a little flapper thing thats serves to prevent convection from carrying hot water out of tank while not in use.
Originally Posted By: psmothers This post was automatically imported from our archived forum.
Thanks for the pics Chad. I had not seen that type before. You stated that some have a line down the center. Is is simply scribed in the pipe or is it colored?
Originally Posted By: Guest This post was automatically imported from our archived forum.
Most have a groove in the middle, and if there’s a groove it’s dielectric. These pictured don’t have a groove, and I’ve seen a few like these. Usually, if there’s a three inch nipple on each side it’s likely that it’s dielectric. If there’s no groove there’s no good way to find out w/o disassembly.
Originally Posted By: jpeck This post was automatically imported from our archived forum.
Chad Fabry wrote:
Some of them even have a little flapper thing thats serves to prevent convection from carrying hot water out of tank while not in use.
Those are called 'heat trap fittings' or heat trap nipples, however, I've always heard them called just 'heat traps'. Down here, either a heat trap fitting, or a heat trap (made out of the piping system piping) is required by the energy code.
Those dielectric nipples are also not referred to as 'dielectric unions', because the 'union' part is like those shown in the photo Foxe linked to. Just a minor correction.
Originally Posted By: Guest This post was automatically imported from our archived forum.
Thanks Jerry
Damned if I could think of the heat trap thing when I was writing and the union part was plain oversight.
I take solace in the fact that I'd have corrected you if you made the same mistakes. I have to admit, I'd do it just for sport with no thought to educational benefits what so ever.
Originally Posted By: syared This post was automatically imported from our archived forum.
Are the water heaters being in series really “incorrect”? Or is that just a different type of installation and we could explain the benefit of changing the installation. Or is this listed in IRC?
Originally Posted By: Guest This post was automatically imported from our archived forum.
The water heaters aren’t really “incorrect” ; either series or parellel plumbing is acceptable. I mention series plumbed heaters only because A.O. Smith suggests parellel as a preferred installation. Honestly, it’s a non emotional issue for me.
Originally Posted By: jpeck This post was automatically imported from our archived forum.
Chad Fabry wrote:
I mention series plumbed heaters only because A.O. Smith suggests it as a preferred installation.
?? Chad, A O Smith prefers parallel, right?
The reason A O Smith gives is that the life of the first water heater in a series installation is shorter than the life of the second water heater. In parallel, they are both just as short. 
Once you set the difference in life aside (likely only months difference from years of life, and did one just 'go bad' sooner anyway, or was it because it was the first one in series?, what if the second one 'went bad' first?), there are those who prefer parallel and those who prefer series, and each side has good reasons to support their preferred choice.
Series or parallel ... the search for that answer is the source of a long and happy life.
Originally Posted By: jpeck This post was automatically imported from our archived forum.
Chad Fabry wrote:
Honestly, it's a non emotional issue for me.
Are you implying that I'm 'emotional' about this issue? Well, then, here's an 'emoticon' for you - 
