What is a dialecric union and exactly where is it located? What does it do?

It is on top of the water heater, connecting a galvanised nipple to the copper piping system. In my area, they tend to attract every mineral in the water and clog up. The proper name is dielectric union.



Post Edited (08-28-03 21:30)

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"You can't get there from here"
Berry/Buck/Mills/Stipe

When you have dissimilar metals such as ferrous and non ferrous,copper connected to steel, it creates an electrolis which will cause that joint to corrode and leak over a period of time.It looks like a regular pipe union,But has a plastic sleeve on the copper side of joint,can be located any where.

Thank you for the information

Thank you for answering. I think I get it now.

Used on water heaters to slow down electrolysis.

Copper flexes work as a dyelectric union also, much easier to work with.

6" of brass, like a 6" brass nipple, will also do the job.

-Steve G

Copper water heater flexes work as a dielectric union but stainless flexes are far superior for that.

Besides lasting longer and staying flexible longer, the main reason that I use stainless flexes between copper and steel water heaters (98% of all water heaters today are still made out of steel) is that stainless steel is a metal that is in between copper and steel as far as metal elements is concerned.

What I mean is that we plumbers should not only deal with electrolysis by breaking the electrical connection but also the dissimilar metals problem.

Stainless steel is a great metal between the two dissimilar metals. Much better than a copper flex.


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Plbg.com's sponsor sells great stainless steel water heater connectors:

[www.plumbingsupply.com] wrote:



Post Edited (08-29-03 10:13)

Steve,
I asked about brass a while back and couldn't get a straight answer. Is 6" the minimum you can use to isolate the two metals to prevent electroylisis? I have a few places where I need to join copper to galvanized. I have also thought about using schedule 40 PVC nipples.
Brian

SCH 40 PVC NIPPLES

YOUR KIDDIN RIGHT?

No I wasn't kiddin, except I meant schedule 80 nipples. The location is a crawlspace under a home in the southwest desert. I need to replace the deteriorated galvanized piping laying in the dirt but I am not ready to tear up the walls yet so the piping in the walls will need to remain for one or two more years till I can afford to remodel. The piping that is not lying on the ground is in remarkably good shape but the parts on the ground are pretty far gone.
Brian

Post Edited (08-29-03 22:44)

Schedule 80 nipples inside the house might be one of the worst ideas you have had in a long time.

Be careful when installing any non metallic piping into an existing water system. Many homes have grounds that go to the water pipes. Electrical grounds, telephone wire grounds, fridge, and washer machine grounds. If non metal pipe is installed or a dielectric union, this ground could be lost and a liability could be found. I prefer dielectric nipples over unions and rather use brass nipples than anything. GOOD LUCK

Except that stainless steel flexes, if you mean the braided ones, are not carrying the water. That is done by a rubber tube inside the flex, which can deteriorate and rupture.

Could you explain why? What would be so different about sch80 nipples under the house as compared to plastic PEX fittings inside the walls?
And what about brass? Would I need 6" or would 3" be long enough?
Thanks,
Brian

Thanks HT but no worry here, my home has none of these once accepted but now illegal grounding methods.
BrianW (electrician)

Good deal "Sparky" (I usually call all the electricians this on the job) As for as 6" of brass I don't know. The most common dielecteic nipple comes in 4" lenght. Good Luck

I love this site.

We can all learn something. Even people who I consider top experts.

Guess in your area they don't offer those as it sounds like you haven't seen them?

I've been installing all stainless flexes water heater flexes for over 10 years.

Not braided, not with plastic lining.

They look just like your copper flexes except the material is stainless.

Picture your copper water heater flexes.

Now picture the identical picture but instead of corrugated copper....it is stainless.

Far superior product and not much more expensive.

Easy to recognize the reasons why they are so superior as connecting copper and steel tanks with stainless in between it is far better for electrolysis.

Also I have found after ten years that they don't become as hard as copper flexes.

You can buy them online at Plumbingsupply.com

Jim

p.s.
These non braided, all stainless flexible connectors also come in 1" and 1 1/2" and are great for water softneres and commercial water heaters.



Post Edited (08-30-03 00:26)

My local codes state that 6" brass separation is the minimum.

If this is truly a temporary situation, you may get away with a 3" brass nipple for a while, although it would seem to be just as easy to use 6" nipples in most cases. I would not recommend using PVC.

-Steve G

Thanks HT. I guess I will go with brass at six inches. There will only be a few of these anyway.
Brian

Thanks for the help Steve. I have a schedule 80 pipe now running undernearh the house in a 2 foot crawspace. It was put under the house to run to irrigation on the other side of the house. It has been in place for at least the five years I have lived there. Do you think I should change it to copper? Keep in mind it will not freeze under there as I am in a desert climate. All the irrigation pipes are pvc.
I will use brass for the transitions. It would be too much of a pain to use plastic anyway with the soldering and all.
Brian

They sell both here, but the DTU's sell the braided ones.

And who says that plastic PEX fitting ARE good inside a house?
1. PVC nipples of either schedule can snap off at the thread.
2. PVC is almost universally banned inside a building.
3. Even if it is not banned it can never be used on hot water piping.

Thanks for the answers hj. I am going to use 6" brass nipples. At one point I thought about using PEX because of the limited working space but instead I am digging out work areas.
Brian

I just use a 3/4" brass FIP's on all my HWT's, they have worked fine for all my tanks with no problems. they will easily last longer than the tank.