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Old 17-05-2018, 20:30   #1
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Sealants for Holding Tank Fittings?

Hey gang-

We just purchased a new Ronco holding tank for our (new to us) 1984 Tartan 28. Having just spent a few days removing the original cracked Kracor tank, I never want to do this job again!

So, I just received the tank and fittings from Ronco (they were wonderful to deal with btw). The Ronco catalog recommends Teflon plumbers tape as the sealant for the inlet and outlet fittings. It also specifically counsels against "compounds such as sealants, pipe dopes, greases, petroleum jellies, glues or adhesives..."

Sooo...does anyone have a favorite technique or product for holding tank nylon fittings in a polyethylene holding tank?

I am personally inclined to go with the Teflon tape recommendation, but wanted to check here if there were any major "yeas or nays" or other recommendations.

Thanks gang!

Kupe
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Old 17-05-2018, 21:26   #2
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Re: Sealants for Holding Tank Fittings?

I would rely on the tank manufacturer for reccomendations. Many pipe sealants are not suitable for use on plastics and will cause stress crack failures over time. Rector seal was great for steel pipes but would cause almost 100% failure on plastics.
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Old 17-05-2018, 21:42   #3
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Re: Sealants for Holding Tank Fittings?

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I would rely on the tank manufacturer for reccomendations. Many pipe sealants are not suitable for use on plastics and will cause stress crack failures over time. Rector seal was great for steel pipes but would cause almost 100% failure on plastics.
Wow thank you! Because I was actually looking at Rector Seal tonight at Home Depot. It mentioned Polyethylene on the list of acceptable uses, but not Nylon, and not dissimilar plastics in general.

Funny how one cracked holding tank will scar you forever LOL!

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Old 17-05-2018, 21:43   #4
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Re: Sealants for Holding Tank Fittings?

I've heard not to use teflon tape for plastic pipe/fittings, but I'm guessing this comes from people using it on household white PVC. Tighten it down hard and it cracks the female fitting, either right away or worse, after it's been in service a while.

BUT polyethylene is not PVC, and is generally very ductile. Considering teflon tape is recommended by the manufacturer, I can't imagine any justification for going a different route. Just don't over do it and don't over tighten it.
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Old 18-05-2018, 03:00   #5
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Re: Sealants for Holding Tank Fittings?

Greetings and welcome aboard the CF, Kupe.
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Old 18-05-2018, 06:07   #6
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Re: Sealants for Holding Tank Fittings?

Welcome aboard Kupe! Teflon tape is the ONLY thing to use. Tank fittings are NPT standard, which is slightly tapered--so slightly that it's impossible to see the taper in a "pipe" that short...so you need to be be careful not to OVERtighten hose fittings. That will result in a cracked female fitting, if not immediately within a short time. A maximum of one full turn past hand tight plus enough to aim an elbow where it needs to go is all you need. If it leaks, use more tape.

And if you have more questions, ask 'em BEFORE doing something instead of asking "is that what I should have done" and finding out it wasn't.

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Old 18-05-2018, 07:35   #7
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Re: Sealants for Holding Tank Fittings?

To add to want Peg is saying on tightness.
I like to use a lot of the tape, but only hand tighten, but about as hard as I can turn it by hand. Of course watch for cross threading.
Remember there should never be any real pressure, but you donít want a leak.
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Old 18-05-2018, 08:28   #8
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Re: Sealants for Holding Tank Fittings?

A trick I used when dealing with any plastic female screw fitting was to put a hose clamp around it before threading in the male. Never worried about over tightening or leaks and never had a cracked male fitting
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Old 18-05-2018, 10:04   #9
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Re: Sealants for Holding Tank Fittings?

Quote:
Originally Posted by Kupe View Post
Hey gang-

We just purchased a new Ronco holding tank for our (new to us) 1984 Tartan 28. Having just spent a few days removing the original cracked Kracor tank, I never want to do this job again!

So, I just received the tank and fittings from Ronco (they were wonderful to deal with btw). The Ronco catalog recommends Teflon plumbers tape as the sealant for the inlet and outlet fittings. It also specifically counsels against "compounds such as sealants, pipe dopes, greases, petroleum jellies, glues or adhesives..."

Sooo...does anyone have a favorite technique or product for holding tank nylon fittings in a polyethylene holding tank?

I am personally inclined to go with the Teflon tape recommendation, but wanted to check here if there were any major "yeas or nays" or other recommendations.

Thanks gang!

Kupe
If the MFG said use Teflon tape use it.
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Old 18-05-2018, 10:34   #10
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Re: Sealants for Holding Tank Fittings?

Well this is unfortunate good news.. Unfortunately, I used pipe dope on my new Ronco holding tank fittings and will require a lot of hose taking off. Good news is that it's still clean. Will tackle this when I get home from work.

What is safe to wipe the pipe dope off the tank and fitting threads?
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Old 18-05-2018, 13:50   #11
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Re: Sealants for Holding Tank Fittings?

It's not the male fitting that cracks, it's the female "collar" that does from being "stretched" further than it can be. Putting a hose clamp on it may have prevented you from doing that. Extreme seasonal temperature changes, or lack of 'em, can also be a factor. I've seen fittings that cracked within an hour of putting the hose on 'em, and I've seen it take up to 18 months.

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Old 18-05-2018, 14:53   #12
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Re: Sealants for Holding Tank Fittings?

Thanks everyone for the great replies! Teflon tape applied liberally, and our new holding tank with fittings is leak-testing here at home in our bath-tub as we speak!

Cheers to all!

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Old 19-05-2018, 07:28   #13
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Re: Sealants for Holding Tank Fittings?

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Originally Posted by a64pilot View Post
To add to want Peg is saying on tightness.
I like to use a lot of the tape, but only hand tighten, but about as hard as I can turn it by hand. Of course watch for cross threading.
Remember there should never be any real pressure, but you donít want a leak.
Thanks! I was burning some major brain cells on that last night as I assembled my tank and fittings to leak test it. Just how many ft/lbs (hand/lbs? ) is "hand tight". I mean, if you can still turn it at all by hand, then it wasn't really hand-tight, right? But then, how do you account for a 300 pound guy with the grip of steel LOL!

And of course one has to be very careful when tightening an elbow so as not to inadvertently "cheat" and use the elbow itself as a "wrench handle". Of course hard to grip the thing at all if you don't just a little bit. Gahhh!

Well- great news! Not a drop of leaking last night, so heading to the boat today. Of course I'll be stressing about did I "over tighten" or "under tighten" for a long time, or until the next boat issue crops up LOL!

Thanks gang!

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Old 19-05-2018, 09:25   #14
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Sealants for Holding Tank Fittings?

Way I see it is that I can always tighten just a little more if it was loose to start with, but the nature of pipe thread is an interference fit, if you overtighten it from the beginning you have opened the clearances up in the female portion and except for a little bit of elasticity of the material, your not getting the tolerance to close up again.
Itís like running in a pipe thread tap in too far, once you remove that metal, your not putting it back.

Be real tough I think to overtighten. 1.5Ē plastic nipple by hand, real tough.
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Old 21-05-2018, 14:28   #15
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Re: Sealants for Holding Tank Fittings?

A couple of months ago I had to change a fitting on a Ronco tank and called Ronco for the part and advice. They sold me the replacement fitting and recommended Dap Gutter Sealant in a caulk tube for the threads. So far so good.
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