Plumbing Forum - Professional & DIY Plumbing Forum > General Plumbing Discussion > Water Heaters and Softeners > Corroding Dielectric Union



Reply
 
Thread Tools Display Modes
Old 06-10-2013, 07:09 PM   #1
Noahboa
Junior Member
 
Join Date: Jun 2013
Posts: 5
Default Corroding Dielectric Union

I recently installed a Whirlpool hot water heater (Model No. ND50T122-403) in my home. I connected the water heater to the copper piping in my home using dielectric unions. Within a week or two of installing the water heater I noticed that I would get a burst of brown rust colored water the first time I used the hot water heater after it had sat overnight or while I was away at work. When I disconnected the dielectric unions I could see rust on the galvanized nipple of the dielectric union (see photos). I tried replacing the unions and made sure that I did not over tighten them to ensure that there would not be any inadvertent contact between the dissimilar metals. This did not help and I started noticing the brown rust colored water within days of installing the new unions. When I drain water from the tank at the spigot at the bottom of the tank the water is clear.

Does anyone have any ideas as to what might be causing the corrosion and what I may be able to do to correct the issue? Thanks in advance for your help.



IMG_0780.jpg   IMG_0789.jpg   IMG_0852.jpg  
__________________
Noahboa is offline  
 
Reply With Quote Quick reply to this message
Old 06-11-2013, 03:56 AM   #2
Caduceus
Senior Member
 
Caduceus's Avatar
 
Join Date: Apr 2011
Location: Pittsburgh, PA
Posts: 949
Liked 205 Times on 149 Posts
Likes Given: 116

Default

Try to give us very accurate timeline of the new installation and experiences with the old tank that was replaced. The details are important, because there may be a catalyst causing premature corrosion of your tank. Are you on well or city water? Do you have a softener? How hot do you set your tank? Stuff like that may help us.
If you run your water for a bit and the rust starts, it sounds like the tank body is corroded inside. Just rusting in the nipples usually doesn't show much in what comes out of the faucet.
Shutting the water down during the tank/union change and turning it back on may cause discoloration from the backwash in the pipes, but that goes away soon. Also, if you run the hot water for 5 minutes straight, is the water coming out rusty the whole time or just in the beginning?
Even some photos of the surrounding area and connected piping for the new install may help. Please understand this can be a tricky thing to diagnose without being there.



__________________
Caduceus is online now  
 
Reply With Quote Quick reply to this message
Old 06-11-2013, 06:48 PM   #3
Noahboa
Junior Member
 
Join Date: Jun 2013
Posts: 5
Default

Caduceus,

I first noticed the brown water approximately 1.5 to 2 weeks after the installation. I did experience a similar problem with my old tank but this was only after it sat unused for a week or more when we were gone on vacation. With the new tank it only has to sit overnight before I observe the brown water. The water is only brown for a short while after I turn on the hot water. Maybe 1-2 seconds after it has sat for roughly 8 hours. I have city water and no softener. My tank is set to 120 deg F. I don't observe any brown water when using just the cold water. I have attached a few photos of the heater. Thanks for your help.

IMG_0775.jpg   IMG_0776.jpg  
__________________
Noahboa is offline  
 
Reply With Quote Quick reply to this message
Old 06-12-2013, 02:31 AM   #4
Caduceus
Senior Member
 
Caduceus's Avatar
 
Join Date: Apr 2011
Location: Pittsburgh, PA
Posts: 949
Liked 205 Times on 149 Posts
Likes Given: 116

Default

From what you have told me I am more enclined to believe the problem is in your pipes and not the tank. If you can try a few tests, they may help to solve this mystery. First, shut the cold water supply to the tank off. Be careful not to scald yourself and open the T&P valve (temperature and pressure) on the upper right part of your tank with a clean bucket at the end to retrieve some water. Only let it out for a few seconds and click the valve closed. See if the water is rusty. With the cold water still off, open the boiler drain at the bottom of the tank, with a hose attached to it and do the same to see if the water is rusty.
I'm thinking that there is a possibility that there are either old steel pipes or old valves, maybe both, on the hot water system and that is causing the rusty water to develop. If there is a dead ended pipe or an unused branch of pipings, the rust will collect and when you turn the water on it gets flushed out.
Try what I've recommended and look around at the piping in the house and see if you can find anything like the circumstances that I've described.

__________________
Caduceus is online now  
 
Reply With Quote Quick reply to this message
Old 06-13-2013, 03:22 AM   #5
Noahboa
Junior Member
 
Join Date: Jun 2013
Posts: 5
Default

When I drain water from the tank, it comes out clear and not rust colored. If my problem is due to rust in my pipes there are two issues which I don't feel it explains. First, why would the condition have become so much worse after installing the new water heater and secondly how would this explain the corrosion I observe on the dielectric unions?

__________________
Noahboa is offline  
 
Reply With Quote Quick reply to this message
Old 06-13-2013, 03:41 AM   #6
havasu
Administrator
PLF_ADMIN.png
 
havasu's Avatar
 
Join Date: Jan 2010
Location: Southern California
Posts: 6,672
Liked 525 Times on 433 Posts
Likes Given: 81

Default

I would recommend a different type of dielectric union (the ones I use are about 4" tall and are made from a stainless steel material) but that would be alot of work which would including cutting and soldering.

__________________
havasu is offline  
 
Reply With Quote Quick reply to this message
Old 06-13-2013, 12:37 PM   #7
johnjh2o
Senior Member
 
johnjh2o's Avatar
 
Join Date: Jul 2011
Location: Melbourne, Florida
Posts: 2,602
Liked 438 Times on 345 Posts
Likes Given: 282

Default

May not have anything to do with your problem but what are the water lines at the bottom of the heater? One of them appears to have a galvanized union connected to it.

__________________

John

johnjh2o is offline  
 
Reply With Quote Quick reply to this message
Old 06-14-2013, 01:03 PM   #8
Noahboa
Junior Member
 
Join Date: Jun 2013
Posts: 5
Default

Havasu - I have checked two different hardware stores and the only dielectric unions they had are the ones I installed. Do you have to go to a plumbing retailer to find the ones you refer to?

johnjh20 - The water lines at the bottom of the water heater are copper. I think what you are seeing is the gas line which runs in front of the water lines.

Is it possible that there is a short somewhere within the water heater that is driving the corrosion of the dielectric unions? Is it likely that replacing the water heater will solve the problem?

Thanks.

__________________
Noahboa is offline  
 
Reply With Quote Quick reply to this message
Old 06-14-2013, 01:51 PM   #9
havasu
Administrator
PLF_ADMIN.png
 
havasu's Avatar
 
Join Date: Jan 2010
Location: Southern California
Posts: 6,672
Liked 525 Times on 433 Posts
Likes Given: 81

Default

The dielectric unions I purchase come from either Lowe's or Home Depot's big box store. Remember though, I am just a handyman and not an expert like John, Phish or Cad.

__________________
havasu is offline  
 
Reply With Quote Quick reply to this message
Old 06-15-2013, 03:32 PM   #10
camaroderrick73
Senior Member
 
camaroderrick73's Avatar
 
Join Date: Apr 2013
Location: Sacramento, California
Posts: 152
Liked 30 Times on 29 Posts
Likes Given: 1

Default

New water heater do not rust out in 2 weeks. The water lines look installed properly to me. The test you did tells me that the water heater is not the issue. Now here in ca we normally use stainless water flexes (24 inches) to attach the copper the the galvi nipples.



__________________
camaroderrick73 is offline  
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Rotating union for a hose-reel??? Scavenger General Plumbing Help 3 04-30-2012 09:36 PM
PVC union peasthope Plumbing Products 2 11-18-2011 01:54 PM
Do I need dielectric for this? KwaiChang General Plumbing Help 4 11-02-2010 05:15 PM

Newest Threads

Job