Seeping threaded fittings... *stainless/brass plastic*

[Deuce]

Hi all, just joined to try and get a definitive answer on this!

When connecting threaded fittings, metal of plastic, what single application thread seal product works best?

We have tried:

• PTFE + silicone. Virtually always seals but will seep if agitated after cured.

• PTFE with Fernox general purpose thread sealant, still sometimes seeps on larger threads 1" or over, and can also fail if agitated after cured.

And also just silicone on some ABS/PVC threaded fitting, as advised by the manufacturer (PTFE can react apparently).

We have to quite often adjust the layout of the kit we assemble and we need to be able to make and break threaded connections relatively quickly, cleanly and not waste time re-working seals as we currently do sometimes. We use threads up to 2" max.

Cost of solution is really not an issue as it's having way more impact on time than we can afford as it is. We also need to be really confident our kit will not leak/seep at all.

I have been looking at Loctite 5776 (LOCTITE 5776 - Thread Sealant - Loctite) and wondered if anyone here had used it, or similar, or could reccomend another product.

I guess as it's so important we don't get leaks, products used reliably for gas might prove most appropriate?

Many thanks in advance

David

 

[ShaunCorbs]

577 is great but won't work on anything plastic

Sounds like you need loctite 55 or boss white and hemp

 

[Chalked]

As Shaun says . Don't use 577 on plastic! It ONLY works with metal.

 

[Deuce]

Thanks both of you.

How reliable/foolproof is 577 generally? For example silicone smoothed into first few threads is normally extremely reliable, initially. But it's not reliable long term. So we need a high tech product that seals as reliably but also copes better with a little movement over time. Can't use a thread 'lock' product though as we do need to be able to break the connections sometimes..

 

[ShaunCorbs]

Never had a leak and you can disassemble when you need to

 

[Deuce]

Have you used on threads up to 2"? And I assume just the 577, no other products used alongside it?

 

[ShaunCorbs]

Yep and straight medium non tapered pipe

Even done an pita 4" one that was in a floor

Follow the spec tho eg need to clean the cutting oil off before you apply it

 

[Last Plumber]

Hi all, just joined to try and get a definitive answer on this!

When connecting threaded fittings, metal of plastic, what single application thread seal product works best?

We have tried:

• PTFE + silicone. Virtually always seals but will seep if agitated after cured.

• PTFE with Fernox general purpose thread sealant, still sometimes seeps on larger threads 1" or over, and can also fail if agitated after cured.

And also just silicone on some ABS/PVC threaded fitting, as advised by the manufacturer (PTFE can react apparently).

We have to quite often adjust the layout of the kit we assemble and we need to be able to make and break threaded connections relatively quickly, cleanly and not waste time re-working seals as we currently do sometimes. We use threads up to 2" max.

Cost of solution is really not an issue as it's having way more impact on time than we can afford as it is. We also need to be really confident our kit will not leak/seep at all.

I have been looking at Loctite 5776 (LOCTITE 5776 - Thread Sealant - Loctite) and wondered if anyone here had used it, or similar, or could reccomend another product.

I guess as it's so important we don't get leaks, products used reliably for gas might prove most appropriate?

Many thanks in advance

David

I take it this is a threaded joint?
What are you putting together?

 

[Deuce]

Yep and straight medium non tapered pipe

Even done an pita 4" one that was in a floor

Follow the spec tho eg need to clean the cutting oil off before you apply it

That's very reassuring to hear! I'll get it ordered.

Yes we clean the fittings, we use loctite spray cleaner.

Thank you so much for the help

 

[Best]

Don't use actual Boss White on anything plastic. It is oil based and will react with most plastics and destroy it

 

[Deuce]

I take it this is a threaded joint?
What are you putting together?

Yes, threaded fittings. Everything else we don in solvent weld as far as possible.

The equipment itself is mostly pool filters/pumps. Which are normally all done with solvent weld. But we have to make the kit modular, mobile and very tough, so we often go onto stainless/brass fittings. We use composite bulkheads to go from one to the other unless we have no choice but to directly mate metal and plastic threads..

 

[Deuce]

Don't use actual Boss White on anything plastic. It is oil based and will react with most plastics and destroy it

Thanks. As it happens I just ordered Loctite 5331 for the plastic threads. So should be all OK.

 

[ShaunCorbs]

Loctite 55 for metal to plastic threads
Loctite 577 for metal to metal threads

 

[ShaunCorbs]

Thanks. As it happens I just ordered Loctite 5331 for the plastic threads. So should be all OK.

Never tried that myself let us know how you get on

 

[Last Plumber]

Yes, threaded fittings. Everything else we don in solvent weld as far as possible.

The equipment itself is mostly pool filters/pumps. Which are normally all done with solvent weld. But we have to make the kit modular, mobile and very tough, so we often go onto stainless/brass fittings. We use composite bulkheads to go from one to the other unless we have no choice but to directly mate metal and plastic threads..

I see. I was asking just to make sure that they are taper threads and not face joints.
If you've sorted it, then all's well and good.

 

[Deuce]

I see. I was asking just to make sure that they are taper threads and not face joints.
If you've sorted it, then all's well and good.

Most are taper threads, some straight. For straight we normally apply sealant on male and female, rubbing it down right into the threads before assembly. This generally means the sealant isn't just pushed down the female thread. Obviously a lot is... But we don't have to worry about contamination as not potable water. Also anything that is pushed down the thread, will get picked up by filters down the line.

But is there a better way for straight threads?

 

[Last Plumber]

Most are taper threads, some straight. For straight we normally apply sealant on male and female, rubbing it down right into the threads before assembly. This generally means the sealant isn't just pushed down the female thread. Obviously a lot is... But we don't have to worry about contamination as not potable water. Also anything that is pushed down the thread, will get picked up by filters down the line.

But is there a better way for straight threads?

More often than not, yes.
What make/ type of fitting are you using and I'll let you know if there is a better way.

 

[Deuce]

This kinda stuff..

Low Pressure Stainless Steel Fittings - Dual Pumps

Or

Low Pressure Brass Fittings - Dual Pumps

From any number of manufacturers. We often get very short lead times and have to hunt the UK for stock.. But essentially, brass and stainless. Typically 1" - 2".

 

[Last Plumber]

This kinda stuff..

Low Pressure Stainless Steel Fittings - Dual Pumps

Or

Low Pressure Brass Fittings - Dual Pumps

From any number of manufacturers. We often get very short lead times and have to hunt the UK for stock.. But essentially, brass and stainless. Typically 1" - 2".

Most look like taper threads. The ones that aren't sometimes you can get a fibre washer to sit in the female if there is a shoulder inside so that the male will screw right down onto it but that is normally only possible when the male will screw fully in easily, as in parallel threaded or not tapered enough to tighten into the female thread, if that makes any sense at all?

Do you use BES?

 

[Deuce]

Most look like taper threads. The ones that aren't sometimes you can get a fibre washer to sit in the female if there is a shoulder inside so that the male will screw right down onto it but that is normally only possible when the male will screw fully in easily, as in parallel threaded or not tapered enough to tighten into the female thread, if that makes any sense at all?

Do you use BES?

No shoulder in the female sockets usually. Yes even parallel threads often don't go all the way without quite some effort... plus the thread itself isn't often fully cut for the last 10mm of some fittings. With parallel we probably get less leaks though, as we simply got OTT with sealant. which is messy, yet effective.

We do use BES and others. It really depends what we need and lead time to be honest.

 

[Last Plumber]

I tend to use Loctite 55 on metal threads. Never tried it on plastic though.

 

[quality]

Sorry to butt in here but Ive used 577 since it was introduced in the early 90`s is 5776 something new?

 

[Deuce]

Sorry to butt in here but Ive used 577 since it was introduced in the early 90`s is 5776 something new?

It's just a variant within the range, fast curing. Which for us is good.

 

[quality]

I will stick with 577 it ok above 60 degrees but 5776 maybe cheaper

 

[Deuce]

I will stick with 577 it ok above 60 degrees but 5776 maybe cheaper

The only difference I can see is that 577 says it will lock the thread, whereas 5776 says only seal. Price is the same, £20 ish for 50ml (without discount).

As for price, I would pay £300 a tube for something that was always 100% reliable. £500 if it was overseas work

Our work goes into TV & film studios with 400v power cables strewn across the floor, £200k per day downtime costs etc.. threaded fitting are not the most popular subject in our workshop..

 

[quality]

Hey ho everyday is for learning

 

[Chuck]

As for price, I would pay £300 a tube for something that was always 100% reliable. £500 if it was overseas work

Our work goes into TV & film studios with 400v power cables strewn across the floor, £200k per day downtime costs etc.. threaded fitting are not the most popular subject in our workshop..

Try calling the Henkel/Loctite Technical hotline:

Contact & Services - Loctite

I've never called them myself, but they're a serious outfit so I'd expect them to know their stuff.

 

[Deuce]

Try calling the Henkel/Loctite Technical hotline:

Contact & Services - Loctite

I've never called them myself, but they're a serious outfit so I'd expect them to know their stuff.

I did just before posting on here - they transferred me to the right department and all I got was a voice recording saying technical services were down due to a technical fault haha!!!

But yes, given their prominence (and prices) I'm sure on a normal day their tech support is first rate.

 

[oz-plumber]

I can't fathom how you are having so many problems with threaded fittings.
You are obviously having major problems, hence coming on here.

Are you putting the tape on the correct way?
Is the tape not gripping to the plastic fittings and spinning / slipping.
Try roughing the threads up a little, so the PTFE grips to the thread.

We did some waterlines recently that were between 1400kPa & 1600kPa, used PTFE tape on all the threaded fittings and didn't have one drip. The largest fittings were 50mm

 

[rpm]

Hi all, just joined to try and get a definitive answer on this!

When connecting threaded fittings, metal of plastic, what single application thread seal product works best?

We have tried:

• PTFE + silicone. Virtually always seals but will seep if agitated after cured.

• PTFE with Fernox general purpose thread sealant, still sometimes seeps on larger threads 1" or over, and can also fail if agitated after cured.

And also just silicone on some ABS/PVC threaded fitting, as advised by the manufacturer (PTFE can react apparently).

We have to quite often adjust the layout of the kit we assemble and we need to be able to make and break threaded connections relatively quickly, cleanly.

Many thanks in advance

David

The equipment itself is mostly pool filters/pumps. Which are normally all done with solvent weld. But we have to make the kit modular, mobile and very tough[/QUOTE]

Pool pumps & filters are quite low pressure things even on 2" so don`t see why you struggle.
You tried these?
Mega Union coupler | Bosta UK Ltd
Come threaded for plastic or metal pipes or solvent weld

 

[Deuce]

Pool pumps & filters are quite low pressure things even on 2" so don`t see why you struggle.
You tried these?
Mega Union coupler | Bosta UK Ltd
Come threaded for plastic or metal pipes or solvent weld

Yes we use hundreds of those a year. Fantastic as the seal is perfect each time and allows components to be switched out in moments, tool free. But sadly the pump/filter ports themselves are threaded, so threaded seal connections still exist in the system. We don't struggle so much with the pool kit really though. But when we have 3000 solenoids all with threads going into a single distribution manifold, all of which have to be (and remain) leak free, even a 99% success rate would mean 3 leaks per assembly. So that's why we're looking for quick and foolproof sealants to use.

 

[Deuce]

I can't fathom how you are having so many problems with threaded fittings.
You are obviously having major problems, hence coming on here.

Are you putting the tape on the correct way?
Is the tape not gripping to the plastic fittings and spinning / slipping.
Try roughing the threads up a little, so the PTFE grips to the thread.

We did some waterlines recently that were between 1400kPa & 1600kPa, used PTFE tape on all the threaded fittings and didn't have one drip. The largest fittings were 50mm

Not major problems, it's just the sheer number of connections and importance of zero drips that makes me seek the ultimate product/method.

But what you have said is quite concerning. PTFE is not generally good for plastic threads. It increases the internal pressure on the female fitting, which combined with a medium to long term reactions with certain plastics can cause the fitting to split. We have had that happen. As your lines were 14bar pressure any such additional pressure on the fitting could be critical.

The thing is, I agree PTFE does work very well on plastic fittings. Initially. But it's a thread lubricant, sot sealant. Any future agitation and drips tend to start. And over time as the tape shifts and compresses the same can happen. But the worse thing is, the reason it works so well on plastic is it allows you overtighten the fittings - causing a fantastic seal initially but at the expense of over-stressing the female fitting.

It does depend entirely on the type of plastic fitting of course. If it were a GF reinforced PP fitting, as many pressure fittings are, then no problem. That stuff's near indestructible. But ABS and especially PVC, teflon tape is really not correct.

We genuinely have had quite a few 1.5-2" PVC threaded fittings split due to the use of PTFE. None were above 3bar pressure. And none split due to water pressure, it was the non-design force from the PTFE that did it. Most common when we combined PTFE with silicone as this made over-tightening very easy by even the most sensitive of hands. That was in the early days and not used PTFE of plastic since.

 

[oz-plumber]

How many wraps do you do with PTFE tape on each size of fitting?

If someone asked me for a quick and fool proof method of sealing a threaded joint - I would reply PTFE tape.

For pool equipment under minimal pressure, I wouldn't consider using anything else on any size of fitting

 

[oz-plumber]

My post may seem not to answer the question - we were posting at the same time.

If you are having fitting split after a while due to stress on the fitting due to PTFE tape, I would find another type of fitting.
I would put that down to the quality of the plastic in the fitting not the jointing method

 

[Deuce]

How many wraps do you do with PTFE tape on each size of fitting?

If someone asked me for a quick and fool proof method of sealing a threaded joint - I would reply PTFE tape.

For pool equipment under minimal pressure, I wouldn't consider using anything else on any size of fitting

It really depends on the exact scenario and fittings to hand. Generally 3-4. That doesn't remove the issue of extra pressure on the female fitting though as you don't know whether or not the tape shift/creases/folds as it's tightened. 4 wraps could in one spot be the equivalent of 7 wraps.

You're outside of most manufacturers advice when it comes to the use of PTFE on plastic. Although, if you're not willing to consider anything else, I guess you have no option!

The only manufacturer I have spoken to that does say teflon tape is ok is spears. But even they stipulate no more than two tooled turns of the threads beyond finger tight. Effectively leaving at least half the thread exposed in most cases. And in any case, they like others prefer the use of sealant in general.

It also has little to do with line pressure. Yes swimming pool kit is relatively low pressure. But I have seen pvc fittings split due to PTFE use on drained systems sat in storage.

 

[Deuce]

My post may seem not to answer the question - we were posting at the same time.

If you are having fitting split after a while due to stress on the fitting due to PTFE tape, I would find another type of fitting.
I would put that down to the quality of the plastic in the fitting not the jointing method

We do keep crossing posts but all useful stuff!

Yes I agree. and per my last post, this may well be why Spears are OK with PTFE tape. The quality and conformity of their fittings is above average imo. Perhaps the worse fittings we have come across are the 'mega' fittings range. We once had a union roll off onto the workshop floor and split. We ripped it apart for a closer look and there were voids in the PVC wall!! I would think that more premium fittings are weighed during production for conformity.


But still the fact remains - PTFE can apply spot pressure to the female fitting which increases failure potential. And it will often drip if agitated after an initially successful seal. It's a common enough problem and if you google it, it's not hard to find examples and various experts explaining at length the reasons why it's not ideal.

 

[Deuce]

So.. the 5776 arrived this morning. I grabbed a couple of old 1.5" fittings, one brass, one stainless and applied to product to the male thread, and finger tightened. I left it about an hour and noticed the product was still fully liquid, I had expected it to gel over at least. But anyway, it said it would work after a few minutes so I hooked it up to a pressure tank we have and then wound the pressure up to 3 bar. That was 2 hours ago and no drips. Not bad for old fittings, finger tight and no real care in the application of the product.

So I'm very happy so far! It still hasn't 'cured' in any way. I'm not sure if it will - but clearly whatever it's doing inside the threads in working. It's also locked the two fittings together very well. I'm sure I could break them apart if I tried but already better than PTFE when it comes to resisting movement.

When i've broken the fittings apart I'll repeat the test, this time applying pressure after just a few minutes. I have a feeling it'll still work fine.

I haven't had chance to try the plastic thread sealant yet, but I'm optimistic based on how well the metal thread sealant works.

So thankyou to all who contributed to this thread - I'm very grateful!

 

[ShaunCorbs]

It won't cure for a long time you can wipe it away once you've finished tightening to make it look neat

 

[Deuce]

It won't cure for a long time you can wipe it away once you've finished tightening to make it look neat

Good to know. And yes it's certainly neater than general sealants we have bought over the counter in the past. This is far better. Even at the price, which is irrelevant really if it works this reliably.

 

[Chuck]

5776 is an 'anaerobic cure' adhesive. For it to cure it requires (a) absence of air (oxygen in fact) and (b) the presence of metal. See here for details:

Thread Sealant | Thread Sealing | LOCTITE® - Henkel Adhesives North America

So, the reason your excess doesn't cure is that it is in contact with air. Clever stuff.

 

[Deuce]

5776 is an 'anaerobic cure' adhesive. For it to cure it requires (a) absence of air (oxygen in fact) and (b) the presence of metal. See here for details:

Thread Sealant | Thread Sealing | LOCTITE® - Henkel Adhesives North America

So, the reason your excess doesn't cure is that it is in contact with air. Clever stuff.

Indeed. I had assumed it would cure due to moisture in the air as many other products do. Far cleverer this way though - gives me a virtually instant seal yet overspill can be easily cleaned no matter how long it's left.

It's exactly the type of high tech solution I was hoping to find. Bit neater than the old fashioned way too haha!

 

[rpm]

Hope that is a left handed thread in the picture.

 

[Deuce]

Hope that is a left handed thread in the picture.

Good spot! I was about to say maybe the image is reversed but looking closely I can see the direction of the thread

And that image was from some sort of guide/tutorial I think!

 

[rpm]

Good spot! I was about to say maybe the image is reversed but looking closely I can see the direction of the thread

And that image was from some sort of guide/tutorial I think!

TBH, anyone copying that would end up having the problems you experienced and some of the things you said about PTFE tape and fittings, lubricant, sealing and split fittings
I`ve never had any of the issues you talk of in 40yrs.

 

[Deuce]

I`ve never had any of the issues you talk of in 40yrs.

You've never used just PTFE on threads and had a drip occur? That's very good going! I'd say we get a drip/seep per 50 or so connections. But that's critical for us. We have to make hundreds in a single assembly sometimes and all extremely tight and hard to access. Also, we can't pressure test as the systems are not closed, or closeable. We really just needed a virtually impossible to fail solution - which it seems we have now.

 

[rpm]

Oh I`ve had drips and seepages which I nip up or add a smear of something on top of the PTFE, even binned fittings if in doubt but the other stuff you talk of, no never! Perhaps it is the quality of the tape and fittings or the experience of how tight is tight that makes the difference.

 

[Deuce]

Oh I`ve had drips and seepages which I nip up or add a smear of something on top of the PTFE, even binned fittings if in doubt but the other stuff you talk of, no never! Perhaps it is the quality of the tape and fittings or the experience of how tight is tight that makes the difference.

Failure to make a perfect seal is the only problem we have that is frequent enough to cause an issue. The splitting fittings was from a long time ago and due to PTFE combined with silicone. Which does make a perfect seal everytime, but also makes it extremely easy to over-tighten.

Sadly we just don't have the time to cope with little drips. If it was plumbing in my house I'd just sigh and do the connection again. But commercially, If I have 300 threaded fittings built into a slim case that requires makes access almost impossible without disassembly, then I stand to lose a lot of time for the sake of just one failed connection.