How To Keep Pipe Fittings Dry: Sealant and Teflon Tape Tests

The article uses the name “Oatley” but it is Oatey, the name and link (there is a spare “space” %20, character in the link preventing it from working) is correct in the contacts section of the print and online article.

It is my experience that threads degrade. Time and tide are a bugger. I have seen this on boats and ships, of course, but on antique cars and Museum relics such as rail cars too. I replace with new whenever I can, and this goes for nuts and bolts as well as fittings

For cleaning female threads- especially on small fittings- I found that a 22 cal. bore cleaning brush works very well and doesn’t take up much room on my toolbox. (It is hard on the hands unless you can find/make a threaded handle for the brush). I also use a home-made pick made from a sail needle (triangular cross-section) set in a wooden handle.

My understanding is that teflon tape and pipe dope should be thought of primarily as a lubricant for threading pipe and fittings.( I too have experience as a master plumber, a pipefitter and as a licensed engineer in commercial and petrochemical plants.) Properly cut threads on pipe and fittings will seal themselves if they can engage with the help of lubricant to overcome friction. The secondary function of those products is to assist in sealing if the threads are not cut correctly or are worn from reuse.

I keep teflon paste on board my 31 as well as some tape. But for exhaust piping and its engine gasket, I use “Never Seize” that is lightly brushed on the threads. It withstands very high temperatures and is an excellent lubricant.

Drew is certainly correct that threads can be damaged or cut wrongly at the factory. Avoid products from foreign countries that have poorly-enforced quality control standards. Sometimes chasing the thread with a tap or die helps but if threads are cut too deep, the joint will likely leak and should be rejected.

When assembling a proper threaded joint, one should be able to turn the fitting 3-3 1/4 turns by hand before needing a wrenches.

This is a symptom of people having to accept low cost crap. Engineering stuff to fail so you have to buy it over and over.
Sadly a Canadian engineers concept from the 1970’s. He worked for a train locomotive manufacturer in London Ontario. He said we are building stuff too well. We need to build it to break so we can sell more parts.
One of the few things I am not proud of my country.
Cheers Rob Legate

You would think that after all this time more modern fittings would be available! We’re still using fittings from the 40’s 🤔 Some one will become a $$$$$$ air ,let’s get going !

Very good article. In my old business in the offshore oil industry, we used the two Loctite sealants in preference to PTFE thread tapes for corrosion protection as much as anything. We found that when joining screw thread fittings for use with salt water, especially when joining dis-similar metals (stainless to galvanised, or stainless to alloy) that after a short while with thread tape, the joints would seize and become wedded for life. The Loctite sealants would allow dis-assembly months or years later.
Be careful when using the word “buggered”. It is an English European term meaning sodomised (which explains its use here) and although I confess we use the term a lot in the marine survey industry, it sometimes causes offense amongst the more straight laced.
Cheers
Al

I asked my engine mechanic what to use on my Westerbeke Diesel engine’s heat exchanger Zinc when you change it every 90 days. He suggested a Teflon paste he said because the zinc and the heater changer or just similar metals. It keeps corrosion to a minimum.

Now, after reading your excellent article, I wonder about using teflon paste at all on the zinc, because of the temperatures involved.

I am not sure if the exhaust and heat exchanger reach 500 degrees I’m worried about toxic emissions from the heated Teflon. The engine heat exchanger is actually in the aft cabin that I sleep in.

What is the best paste to safely use for high temperature applications like the heat exchanger Zinc?

Specifically, What is the best paste to safely use for high temperature applications like the heat exchanger Zinc?

Specifically, What is the best paste to safely use for high temperature applications like the heat exchanger Zinc?

This is not a duplicate comment.

It’s my understanding NOT to use a thread sealant for heat exchanger anode (zinc). A metal to metal electrical connection is desired for the anode (zinc) to function most effectively.

I’ve spent the last 40 years working as a pipefitter and have found that in most applications a layer of Teflon tape followed by a thin coat of Rectorseal #5 is almost foolproof. Also regarding unions, the seal is made at the mating surface and not at threads. A little neversieze on the threads combined with a light coating of pipe dope on the sealing surface takes care of most leaks. The neversieze eliminates some of the friction and allows the union to be tightened slightly more and also makes for easier disassembly when needed.

Don’t use thread sealant on heat exchanger anodes! It will electrically insulate the anode from the heat exchanger and render it useless! I speak from the experience of having galvanic damage occur because I made this mistake!

Thank you for the engine zinc answer. It make’s good sense.

Practical Sailor is a gift to this newbie. Thank you!