dielectric union after the fact

[K6JEK]

This is a plumbing question.  

Is there any way to turn a union into a dielectric union after the fact?

The guys who installed the solar water pre-heater in my house neglected to use dielectric unions for the connections to the regular water heater.  I failed to notice it at the time.  Now a year and a half later I have a lot of corrosion.  

I am trying to track down the original plumber to have him make good on this but if I don't, I figure I'll have to dive in.  It's a regular maze of pipes and valves so either or both of the heaters can be in the loop, so the water doesn't end up too hot and so things can be drained.  Working on it is going to be a fight.

I've attached a photo for your amusement.  

Here's the unit that keeps the water heating bills to a minimum out here:  http://www.tctsolar.com/homeowner.htm

[Bill, KD0HG]

Wow, what a crazy setup.

Here's three suggestions:

You could replace the copper tank fittings with brass ones.
Many plumbers use brass fittings instead of dielectric fittings on water heaters.

There are flexible water heater lines that are also dielectric unions.

OR you could replace the short pieces of copper attached to the tank with CPVC (hot water rated) plastic pipe.

It's fairly easy to cut out chunks of copper pipe with a little pipe cutter.

[k4kyv]

That looks a lot like the back of my audio rack.

[WA1GFZ]

That looks like copper screwed on to a steel nipple coming out of the heater. I seem to remember that fitting has a washer like a garden hose. I used stainless flexable lines on my heater at the new place. I also put some teflon pipe dope on the threads. I bet all you need to do is break that union above and remove the fitting on the steel nipple and clean it up I bet it was just weeping through the threads until the particles in the water sealed the leak. Maybe it will be fine if you just clean the outside.
I would start with a wire brush and clean the area. I would just shoot some paint on the rust if there is no leak.
The steel nipple is part of the heater so I don't think you can change it.
Mr. HVAC will provide the real story.

[Bill, KD0HG]

That looks like copper screwed on to a steel nipple coming out of the heater. I seem to remember that fitting has a washer like a garden hose. I used stainless flexable lines on my heater at the new place. I also put some teflon pipe dope on the threads. I bet all you need to do is break that union above and remove the fitting on the steel nipple and clean it up I bet it was just weeping through the threads until the particles in the water sealed the leak. Maybe it will be fine if you just clean the outside.
I would start with a wire brush and clean the area. I would just shoot some paint on the rust if there is no leak.
The steel nipple is part of the heater so I don't think you can change it.
Mr. HVAC will provide the real story.

I think you're correct. That does look like a thread leak that could be cleaned up and repaired.
On closer inspection, those do look like brass fittings attached to the steel pipes of water heater and if so, they shouldn't corrode.

How long has that been in service?

[W2VW]

I had the same exact problem here.

It killed my hot water tank in 7 years. It looked like Bonnie and Clyde's car.

The new one now has insulated couplings. They go in place of the ones right on top of the tank and have orange plastic insulators.

Many hot water tanks also have replaceable zinc inserts.  

I have everything in this house bonded together. Ground radials, tower base, plumbing and HVAC. The first water heater died a natural death before all the ground work took place. It had no rust on the outside.

[WA1GFZ]

look closer the union above it also leaked for a while. Maybe was a tad loose form the start. My heater had a plastic insert inside the steel pipe. I am anal about teflon tape and teflon pipe dope to avoid these problems. It makes taking things apart later a lot easier.

[WA1GFZ]

I used flexable lines covered with stainless that came from home depot. I still used Teflon pipe dope on the threads.

[KF1Z]

Looks to me like the corrosion was caused by a water leak from the green valve at the top.............(or the leak from the ceiling around the vent-pipe).
Dripping down on the hood, and onto the heater around that one connection.

I'd just clean it up with a wire brush, and stop the leak from above.

[Opcom]

what a mess. yeah the guys have said the right things to do, try and isolate the water heater from the pipes.

Isn't there supposed to be a simple electrical way to prevent the corrosion?  or is that hogwash? i am not sure i understand where the current is flowing in that setup.

So.. my heater has direct pipes to it. one from the main, one to the house. Plus the gas pipe is metal. Do I need to insulate them?

[W3LSN]

This is a plumbing question.  

Is there any way to turn a union into a dielectric union after the fact?

The guys who installed the solar water pre-heater in my house neglected to use dielectric unions for the connections to the regular water heater.  I failed to notice it at the time.  Now a year and a half later I have a lot of corrosion.  

Flex connections are fine in most circumstances, but I presume you are a K6 in earthquake prone territory, so you may want to consider hardpiping it again if you ever expect the water heater to rock n' roll.

We had this same problem on a new water/glycol HVAC system at work. The installers didn't use dielectric unions where the copper pipe connected to the cast iron body of the circulating pump, and I found significant corrosion evident after only 6-months. The corrosion is from the galvanic action of two disimilar metals touching each other. This creates a weak electric current that gradually corrodes the junction. Think of the dielectric union as an insulator.

If the plumbing contractor won't honor his workmanship warranty, you can fix the problem yourself by learning how to sweat solder pipe, and making a trip to your local plumbing supplier for some dieletric unions of the right size, some couplers, nipples, a short length of pipe, and a propane torch. Plumbing is not rocket science.

73, Jim
WA2AJM/3

[W3SLK]

I guess I can add my 2 cents here. FWIW, it looks as though the union is leaking through. I think most people who have commented will agree that hot water heaters have a unique knack for water demineralization, thus the some of the corrosion. If you have to sweat a fitting on to replace the existing one, a neat little hint I learned from our pipe fitters is to stuff a small piece of bread, (I'm not kidding, it works!), where you are sweating the pipe. It will wick the water away and make it easier for the joint heat evenly and take the solder. Otherwise, you wind up with a big solder blob and very leaky joint. Gud Luck.

[W1ATR]

Wow, that actually hurts my brain to look at it. Dielectric union's are a whole different animal. If you have room against the ceiling to push that rack up an inch or so, you will have to heat and remove them from the piping. (Don't heat while connected to the water heater.) From there, you can sweat on a 3/4" copper male adapter to the bottoms of that rack and screw the brass side of the new union to it. clean up that dip tube fitting and connect the steel sides of the new unions to the water heater. Put the washers in and put them together.

Kinda had to make it short and ugly as I have to get on the road now. If you have any Q's, you can click my email to the left and send me a message. I get my email on my crackberry and I'll send you back my number.

The piping is fugly, but that's just calcium from a drip. Don't use white pipe dope and DON'T use teflon tape, but look for a product called 'Blue Blocker'. Clean threads and tight fittings are a must.  

[WA1GFZ]

Jared please explain. I'm an antiseaze, coat every thread kind of loon so interested in any cool product.
I'm thinking that job is so fugly because there was no room in the closet to do a better job....or the guy was a hack

[W1ATR]

The Blue Block?

It's a heavy duty pipe dope made by Hercules. It has a very smooth texture to it and it spreads very nicely into the threads. Unlike others, this stuff semi dries and it won't leak ever. I don't know how or why, but it seals the fittings so well, that you'll need to heat the joint with a torch to get it back apart again. In my opinion, I'd swear it works more like a glue than a sealant because it really REALLY sticks to the materials. That's the downside, you'll need kerosene to get it off your tools, 3 days of showers to get it off your skin, next haircut to get it out of your hair, and it'll never ever come out of your clothes. It has a nice thick, smooth consistency, so you won't have to worry about it dripping off your work.  I've used it exclusively for probably the last 15 years on everything from LP and NG gas installs, water, oil tanks and lines,  all the way to 10Kpsi hydraulic lines. It also works when used for sealing gaskets like circulator flanges and auto thermostat housings. About $10 bucks for a little can and 16 for a big one.


On Edit: heres a quick google link. Scroll down for specs.
http://www.accentshopping.com/product.asp?P_ID=148706#tabtop   

[WA1GFZ]

man I could have used that stuff on my sewer  line under the basement floor. Building inspectore would not let me pour the floor until I demonstrated the sewer line would hold air pressure. I had 1 PVC clean out cap that would weap. I must have put 10 feet of teflon tape on the threads and painted it with teflon dope.
I finally threw a few handfulls of fine silt sand in the pipe and filled 1/2 full of water to seal the threads.

[K6JEK]

Thanks for all the responses.  The plumber is showing up in a week.  I'll keep you posted.

In response to a couple of comments, yes indeed it is cramped in there.
I have used the bread trick myself.  Use white bread, not whole wheat.
Great tip on the pipe stuff.

It hurts my head to look at all that stuff too.  I have to draw diagrams to figure out which way the water is going.  The anti-scald valve makes it all just that much more complicated.

Incidentally, the thing does work. 

[W1ATR]

man I could have used that stuff on my sewer  line under the basement floor. Building inspectore would not let me pour the floor until I demonstrated the sewer line would hold air pressure. I had 1 PVC clean out cap that would weap. I must have put 10 feet of teflon tape on the threads and painted it with teflon dope.
I finally threw a few handfulls of fine silt sand in the pipe and filled 1/2 full of water to seal the threads.

Yeah this stuff would have worked well for that. On a loose thread like PVC threaded plugs, you would apply it to both sides, but it's hell to get it opened again down the road for servicing the drain. Cotton string works good for PVC. I have cotton string on all the cleanouts here and they don't leak at all and are real easy to get out.   

[Opcom]

Looking back at it, I'm wondering whether it would be better for 220 or 70cm.

[N0WEK]

That corrosion seems to be from a minor leak/seepage and wouldn't have anything to do with the lack of dielectric unions. Any corrosion on the outside of the pipe is due to leaking. That said, I never thread copper fittings into steel tanks or fittings and I never use soldered in fittings on threaded connections.

I gave up on dielectric unions after looking at a couple of them a year down the road. If there are ANY stray currents in the piping the dielectric unions are where all the deposited minerals and such go. I've seen unions that were half blocked after less than a year and were still clean on the outside (they weren't leaking)!

I use brass compression fittings threaded directly into the steel tank and bond the hot, cold and gas lines together near the tank. I've never had a problem with leaking or corrosion, inside or outside of the pipe. A plus is that if the threaded connection seeps when you install it, all you have to do is loosen the compression fitting and tighten the fitting; not something you can do with a soldered fitting. Brass and steel go perfectly well together in plumbing, look at all the brass valves in the older iron pipe systems.

[K6JEK]

Gregory, N0WEK called it.  That's a brass connection to the tank and a brass to copper union.  The union was leaking.  The plumber took everything apart and cleaned it up. Nothing seemed to be damaged so he put it back together, tightened it up and watched it for awhile.  No leak.

He asked me to keep an eye on it.  If it leaks, he'll replace the union.

Incidentally, it was the big cheese who showed up.  A guy working for him installed it in the first place.  He checked it out himself this time, charged nothing.  Isn't it great when something like that happens?

Thanks to everyone for the education.