The Tank › dielectric unions/nipples
- January 23, 2010 at 8:51 pm #12703
I have heard numerous comments regarding dielectric connections when piping out water heaters and boilers. What is the real deal with water tanks and dielectric fittings? And should it apply to all dissimilar metals touching water and other metals? The tubibing for hot & cold domestic water? The P&T valve? Mixing valve? My head is spinning.January 24, 2010 at 1:16 pm #12712
Pretty much you should always use them, unless you want something to rust/corrode, leak and make a giant mess. All you have to do is screw a galvanized steel nipple into a brass fitting sometime and in pretty short order, you’ll see what I mean.
You raise an interesting question about the T&P valve, which is brass and screws straight into the water heater. I’m not sure why nobody ever tried to separate the two, but the problem is more urgent in places where water is constantly flowing, such as at pipe nipples.
A corollary to this can be found in Quick, regarding going back and tightening fittings after six months.
Randy SchuylerJanuary 24, 2010 at 2:28 pm #12713
Appreciate that Randy, although most friends of mine tend to go with brass nipples or couplins directly off the tank. They clain the brass will accomplish the same thing. To be on the safe side, for now, I installed brass couplings onto the supplied SS nipples coming out of the Smart-40 and put dielectric nipples into them. Eventually I will probably use dielectric unions there to simplify everything. The P&T valve does pose an interesting question, especially with the indirect tank hitting very high temps.
When I finally settle on the proper piping for the mixing valve, i will change all the domestic water conections. For now, the wife insisted upon having hot water–so in order to sleep with both eyes closed, I piped it out for now. Heat traps!!!:shock:January 24, 2010 at 5:50 pm #12716
Brass does accomplish that — for the brass. But it may cause interesting things to happen inside the tank. Our favorite is where a brass nipple is used on a recirc return, and, reacting with the anode rod, clogs itself up and burns out the recirc pump.
Randy SchuylerJanuary 24, 2010 at 7:26 pm #12720
Interesting, indeed. Even when I install dielectric nipples on a tank, I often find one or both nipples clogged when replacing the tank. I have yet to figure out why. Many times it appears like a rusty colored “cholesterol” clogging the pipe. Any suggestions?January 24, 2010 at 8:31 pm #12723Larry WeingartenParticipant
Hello: My dielectric of choice is to put a plastic lined nipple in the tank. Use the type that has the ends wrapped over in plastic. From there simply a copper flex connector that has a plastic bushing under the brass nut. This combination gives a true dielectric without exposing any steel to the water. It also puts distance between the copper pipe and steel tank. The tank likes it 😀
Yours, LarryJanuary 24, 2010 at 9:24 pm #12724
I have used many standard dielectric nipples but the plastic insert always falls short of the threaded end. Which always makes me wonder how it can possibly work. The flexable connectors I have never tried. I’ll pick up 2 in the morning to see how they might help me.
I must be doing something wrong, for every time I attempt to attach a photo it comes up “error” due to too many bytes. Is there something I need to do to make a simple photo fit?January 24, 2010 at 9:51 pm #12726Larry WeingartenParticipant
Hello: Have a look at this: http://perfectioncorp.com/library/menu/documents/ClearFlowSheet.pdf It shows, (not too clearly) the sort of nipple I’m talking about, with the ends wrapped. This, when used with a copper flex is nice because the rubber washer of the flex presses into the plastic, keeping the steel nipple dry.
I seldom offer computer advice as all I do know about computers is they are out to frustrate me. Still, you might be able to “resize” the photo, smaller, to use up fewer bytes. http://www.irfanview.net/ might be useful 😉
Yours, LarryJanuary 24, 2010 at 9:55 pm #12728
Thank you, Larry I will look into those right now.January 24, 2010 at 10:04 pm #12729
I see the difference, the nipples I usuall use are much more crudely made–possibly China or Tiwan. Then again, we do not do potable/domestic water, only heat and HVAC, and from what I understand in a closed system, dielectric fittings do very little.January 24, 2010 at 11:33 pm #12730
The truth is, Jimmy, I can get plain ol’ plastic-lined nipples like Larry describes, known as fitted-end (FE) nipples, and I can get dip tubes with the same, but every combo anode I’ve come across, from several different sources, comes with a nipple that has the plastic slightly recessed from the steel, something like what you’re describing. I’m still trying to figure out if I can make anybody give me a combo with an FE nipple.
Randy SchuylerJanuary 26, 2010 at 4:58 pm #12748
Ok, I have one of my dielectric nipples in my hand, a 1″ Gruvlok/Di-lok fig 7000, made in USA. The plastic does stick out, maybe, 1/8 of an inch past the threads. It is a heavy duty nipple, better than what I have encountered, where the plastic stops inside the nipple’s threaded ends. I am still searching the basement for one of the many 3/4″ nipples we’ve been using.February 1, 2010 at 3:03 am #12789sky_techParticipant
There’s an extra space (%C2%A0) at the end of your link making it not work. The correct link is:
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