Heat exchanger zinc - teflon tape on threads?

[Kingfisher1]

I recently had my heat exchanger cleaned. It came back with a new pencil zinc threaded in to the brass plug which is good. The brass plug is threaded into the side port of the exchanger with teflon tape on the threads. Seems like this may eliminate the effectiveness of the zinc. Or should I assume the threads of the plug will cut through the tape and make electrical contact with the threads in the exchanger?

[jamhass]

Likely OK, but you can check continuity with a decent multimeter set at a low-ohm scale.

[Jim Cate]

The seating of the threads will cut th rough the thin teflon and electrical continuity will be achieved. The current that flows is tiny and only small contact area will be sufficient.

Above is opinion, backed by years of usage.

Jim

[BillKny]

No problem.

Teflon tape is routinely used in all kinds of marine, industrial and household piping systems were electrical conductivity is required for safety and corrosion control.

Find something else to worry about!

[FPNC]

Teflon tape is not a good idea. Use a pipe dope or just silicone if required. Generally speaking you should not use teflon tape in any system that involves any kind of pump down stream from the tape.

[Jim Cate]

Generally speaking you should not use teflon tape in any system that involves any kind of pump down stream from the tape.

I've never heard that before. Could you please explain why this is so?

Jim

[gonesail]

one thing for sure is the tape will stop any small leaks.

[BillKny]

Originally Posted by FPNC

Teflon tape is not a good idea. Use a pipe dope or just silicone if required. Generally speaking you should not use teflon tape in any system that involves any kind of pump down stream from the tape.

This is a case of taking some very specialized advice and generalizing it beyond what is correct.

There are places where TFE tape should NOT be used because it can shed little bits of stringy debris. This can cause real problems in a diesel injection pump (for example) where there are VERY close tolerances. I'd probably avoid it upstream from a high pressure pump on an RO system, because of the risk of jamming debris in the check valves.

BUT... The idea that a little bit of TFE tape floating around has any potential to cause a problem with a rubber vane water pump">raw water pump is just plain WRONG.

And for what it is worth, pipe dope is WAY better--for a lot of reasons--at sealing pipe threads than silicone.

[skipperpete]

Originally Posted by FPNC

Teflon tape is not a good idea. Use a pipe dope or just silicone if required. Generally speaking you should not use teflon tape in any system that involves any kind of pump down stream from the tape.

Why not? I use thread tape on hydraulics, air fittings, fuel fittings and water line connections on both suction and delivery although I’m now using the loctite dental floss stuff. What don’t you like about teflon tape and pumps?

[Stu Jackson]

Originally Posted by BillKny

>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>


BUT... The idea that a little bit of TFE tape floating around has any potential to cause a problem with a rubber vane raw water pump is just plain WRONG.

>>>>>>>>

True, Bill. Just to add: the HX in this and every other freshwater cooled marine engine I've heard of is AFTER the pump. I know YOU know this, but just for the uninformed...

[rwidman]

My choice when electrical conductivity is important (as in this case) would be pipe dope, not Teflon tape.

If it were my boat, I would remove the anode, remove the tape and reinstall it with pipe dope as the sealant.

[jamhass]

Proper application of teflon tape nicely avoids the possibility of loose threads shedding from the joint.

You "simply" avoid putting tape on the first full thread of the nipple which ensures the tape is only on the internal part of the threaded joint and cannot shed to the inside of the plumbing.

[Manateeman]

Jamhass is correct. The manatee crew is using nickel impregnated tape on all their stainless steel pipe fittings in their new turbo powered beer brewery.
They put Tef-Gel on everything but pizza.
Happy trails to you.
Captain Mark

[GordMay]

Originally Posted by jamhass

Proper application of teflon tape nicely avoids the possibility of loose threads shedding from the joint.

You "simply" avoid putting tape on the first full thread of the nipple which ensures the tape is only on the internal part of the threaded joint and cannot shed to the inside of the plumbing.

Indeed.
But, also be careful how much tape you use. If you use a lot, and do not tighten the thread enough, you can insulate the joint, to some extent.

See also: ‘Thread sealant on engine anodes?’
➥ https://www.cruisersforum.com/forums...es-208156.html

[BillKny]

Originally Posted by jamhass

Proper application of teflon tape nicely avoids the possibility of loose threads shedding from the joint.

You "simply" avoid putting tape on the first full thread of the nipple which ensures the tape is only on the internal part of the threaded joint and cannot shed to the inside of the plumbing.

That is the correct way to install tfe tape, but it is still NOT recommended for critical systems with close tolerances.

Your “simple” solution might work when assembling parts, but there is no simple way to prevent contaminating the inside of the system with shredded tape when you remove a part, or reinstall a part into a fitting that previously had tape on it.

Keep it out of fuel lines and other systems with tight tolerances.