Heat Exchanger Zinc

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Brad Young

Did something pretty stupid this weekend. I wanted to replace the zinc in Heat Exchanger. I could not get the old one out. Well I got out the breaker bar. Then I broke the nipple or flange that the zinc screws into. I did not realize that there was a place to put an opposing wrench. So, the damage is done and is fixed.

I think there was a small drip when I put the since in 6 months ago, so I tighten it up pretty good.

I now want to put in a new zinc. Can I put Teflon tape / copper or Teflon washer on the zinc?
Brad Young
Boat
Year 1986
Model C34
Hull# 84

Kevin Henderson

Brad,  I just went through the changeout of my HX Zinc as well... although without the difficulty that you went through.  As I understand it you cannot or should not use any Teflon tape between the the threads of the Zinc and the HX.  Full metal to metal contact is necessary for the Zinc to work.  I'm certain others will voice their more seasoned insight into the matter than me but to my knowledge.. no Teflon tape.
The sail, the play of its pulse so like our own lives: so thin and yet so full of life, so noiseless when it labors hardest, so noisy and impatient when least effective.
~Henry David Thoreau

Ron Hill

Brad : You need thread to thread contact so you are "electrically" connected.  Use Teflon tape and you could isolate the Zn and then the copper in the HX would arrode instead of the Zn!!

Clean the threads both male and female with a battery terminal tool.  Then see if it will install with out a leak.  If you still have a leak, my advice is to use antiseize on the threads, the copper antiseize would be the best.  That is a tapered pipe thread so no washer will work.   A few thoughts
Ron, Apache #788

Bob K

Brad,
A trick I learned (by accident) to remove a stuck heat exchanger zinc is to run and warm up the engine first. 
Bob K
Prosit
1992 #1186
Northern Chesapeake Bay

Tom Clay

#4
A difference of opinion.... When my boat was delievered new it had teflon tape on the zn. I have used teflon tape for the last 5 years, and never had any leaks. I check the zn every 3-4 months and usually 50% or more is gone so I replace it, it's apparently making a solid connection. In talking to different mechanics it appears they are split on this issue, some use it and some don't.
Tom and Lynn Clay
2006 34' Hull #1760......Somewhere
Olympia, Wa.

Ted Pounds

I would guess that as long as some of the threads are exposed (not covered w/ teflon tape) that you would have a good enough electrical connection for the Zinc to do its job...
Ted Pounds
"Molly Rose"
1987 #447

Bob K

Teflon tape tears very easily  - if you wrap it tightly you can see the threads will cut right through it as you wrap.  So you are still making metal to metal contact. If no contact  the zinc would not corrode.  Having said that, I'd still opt for a conductive sealant like Ron suggested.
Bob K
Prosit
1992 #1186
Northern Chesapeake Bay

Indian Falls

Here's my advice after 30 years of working in fittings: Since it is a tapered pipe thread you can leave the Teflon tape off the first 2-3 threads where it will make more than adequate contact with the HX fitting. 3 wraps of Teflon on the remaining threads will seal if the threads old or new are prone to leak.  Even if you put Teflon on all the threads it is pretty unlikely that running the plug into a taper with a wrench will not obliterate the Teflon on the first thread.  Chance of isolation is pretty small but possible, say, if you screw it in with your fingers only.

If it leaks after this, remove, clean it off, and apply a few more wraps of Teflon tape in the same manner as before.  This only has to hold water for a year or 6 months, so tighten just enough or you'll wear out the permanent part prematurely.  If it leaks and you crank it in more you're just trying to make up for lack of sealant by ramming it in.  This is a maintenance thread, not a permanent threaded connection, so don't use the old addage that you don't use sealant because tapered threads self seal. True, but if you do you'll need a new bushing on you HX in short order.



Dan & Dar
s/v Resolution, 1990 C34 997
We have enough youth: how about a fountain of "smart"?

Ralph Masters

Teflon tape is a lubericant for the threads to assist in obtaining a leak proof seal, not a sealing tape.  Joint sealing compound is ment to seal.

Ralph
Ciao Bella
Ralph Masters
Ciao Bella
San Diego
Hull 367, 1987

Indian Falls

Ralph is correct, but again that is for connections that are meant to stay together for awhile. 
Teflon tape is used to seal between almost all threaded plumbing fittings, whether it be copper, brass, plastic or steel pipe thread.  Brass to brass sort of self lubricates and "usually" no sealant/lubricant is needed there.  Pipe dope contains Teflon or other lubricant as well as the sticky goey petroleum base it's made from.

Tef tape is my choice for a maintenance thread like the zinc plug.  Stick with the tef tape, it's clean and easy if nothing else and still stops leaks in spite of it being a lubricant.  Always make sure you wind it on clockwise when viewing it from the zinc end or it will shred and pile up as it goes in. 
This is not a mandate just some friendly advise.  Over and out.
Dan & Dar
s/v Resolution, 1990 C34 997
We have enough youth: how about a fountain of "smart"?

SeaFever

Guys, it has been said before. The Teflon tape is an electrical insulator and can prevent the electrical connection between the zinc and the HE.

What is the primary purpose of the Zn? To save the engine parts from corroding due to electrolysis. Yes, the secondary, albeit important, purpose is to keep the water leaking from the HE. So keeping the primary purpose in mind, I would avoid any possibility of an impaired electrical connection.

It has also been said that Zn plug has a pipe thread hence it will bite into the HE and make its water tight seal. Yes, it will then also bite into the Teflon and make an effort to make the electrical contact but why oh why would we make it any difficult for it to get the electrical connection? If the water is leaking, there is a reason why it is. Find the reason and fix it.

My two cents...
Mahendra, Sea Fever, Pearson 10M, #43, Oakland, CA

prh77

If you have ever taken apart a fitting sealed with teflon tape, you will note that most of it is missing from the threads. I think the nature of pipe threads strip most of it away. If it stops the leak, I think you will still have plenty of metal to metal contact. Just a thought or 2 cents or whatever.
Peyton Harrison Hull # 597 1988 "Trinity"

Ron Hill

#12
Guys : FACT -- The contact between the threaded plug on the Zn, temperature sender/switch and the oil pressure switch/sender is the ground electrical connection necessary for those items to function properly!!

Just do what ever you please.   Stu's saying --- Your boat Your choice   Out !!   :rolling
Ron, Apache #788

Stu Jackson

#13
Quote from: prh77 on March 26, 2011, 04:49:16 PM
...most of it is missing from the threads. I think the nature of pipe threads strip most of it awayI..still have plenty of metal to metal contact.

Reality check, please.

Most?  Usually just the top of the threads, which means, at BEST, only 1/3 connectivity.

Would you deliberately do that kind of connection on your electrical system?

Yup, your boat, your choice.
Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

"There is no problem so great that it can't be solved."

Brad Young

Here is what happened.

Got the nipple welded back in. Cleaned threads with a battery terminal brush. Put in the zinc, it did not leak.  :clap
I did not have to add Teflon or Anti-Sieze.

Brad Young
Boat
Year 1986
Model C34
Hull# 84